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$3.50 a year.

4.50 a year.

To any contributor, on request in advance, one hundred copies of the issue containing his article will be sent without charge. More copies will be supplied at about cost, also if ordered in advance. Reprints are not supplied, as for obvious reasons we desire to circulate as many copies of Science as possible. Authors are, however, at perfect liberty to have their articles reprinted elsewhere. For illustrations, drawings in black and white suitable for photoengraving should be supplied by the contributor. Rejected manuscripts will be returned to the authors only when the requisite amount of postage accompanies the manuscript. Whatever is intended for insertion must be authenticated by the name and address of the writer; not necessarily for publication, but as a guaranty of good faith. We do not hold ourselves responsible for any view or opinions expressed in the communications of our correspondents. Attention is called to the "Wants" column. It is invaluable to those who use it in soliciting information or seeking new positions. The name and address of applicants should be given in full. so that answers will go direct to them. The "Exchange" column is likewise open.

STATISTICS OF THE MISSISSIPPI RIVER.

BY H. L. WHITING, WASHINGTON, D.C.

PERSONS familiar with the range of tide along the seaboard can hardly realize how much the waters of our great interior rivers are affected by the rainfalls and watershed upon and from the vast surrounding valleys. The records of the Mississippi River Commission give much relevant data in regard to these phenomena. The following figures have been selected, from the voluminous reports of the Commission, to give more briefly a knowledge of facts that do not come before the general public. As an instance of the great rise and fall of the Mississippi River at Cairo at its confluence with the Ohio - in the spring of 1891, at its low-water stage, the surface of the river was within a few inches of the top of the levee that protects the city of Cairo from inundation, and from the deck of the steamer the writer looked down into the streets of the city several feet below the line of the water rushing by with a velocity of nearly seven miles an hour. In the fall of the same year, at the low-water stage of the river, the steamer, at the same place, was fifty-one feet below the elevation at which she floated six months before; and this was not the greatest range of the river at this point.

Difference between highest and lowest water-readings.

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Illinois, Kentucky, and Tennessee...
White and Arkansas Basins (west side of river),
Helena to Arkansas City.....
Yazoo Basin (east side of river), Memphis, Tenn.,

to Vicksburg, Miss...... Macon, Boeuf, and Tennessee Basins (west side

of river), Arkansas City to Red River...... East side of river, Vicksburg to Baton Rouge... Atchapalaya Basin (west side of river), Red

River to Bayou La Fourche.... Pontchartrain Basin (east side of river), Baton Rouge to Gulf of Mexico..

La Fourche Basin (west side of river), Donaldsonville to Gulf of Mexico...

4,955

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Nearly thirty thousand square miles, or three and a half times the area of the State of Massachusetts.

Although, as stated, the high-water depth of the Mississippi River at Cairo is over fifty feet, the low-water depth, on shoals and bars, does not exceed four feet. This great highway to the ocean is, therefore, at these latter seasons, practically unavailable for navigation. Ten of the large steamers of the Anchor Line, which ply between St. Louis and New Orleans, are now laid up, while the elevators of St. Louis have accumulated some nine million bushels of wheat, waiting transhipment. This is but a partial showing of the importance of the improvement of the Mississippi River, in its low-water navigation, to the commercial interests of the country; aside from the injury to agricultural interests from the overflow of the lower basins of the river.

Mississippi River.

St. Louis, Mo....

Cairo, Ill...

53.2

New Madrid, Mo..

41.4

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ON THE USE OF THE COMPOUND EYES OF INSECTS.

BY R. T. LEWIS, EALING, ENGLAND.

FEW subjects connected with the study of insects have given rise to more widely differing opinions than the rationale of their complex organs of vision, the physical structure of which presents to us one of the most elaborate optical combinations to be found in nature, and this, too, upon a scale so minute as to require no ordinary skill on the part of the microscopist to unravel its marvels.

Attempts to work out the problem as to what is the impression produced upon the consciousness of an insect by an arrangement so complicated have seldom resulted in satisfactory conclusions, not a few failures in this respect apparently being due to inadequately clear conceptions as to the application of the laws and phenomena of refraction to the cases in point. But whether the subject is approached from the standpoint of those who regard an organ as having elaborated itself in obedience to the necessities of

1 November, 1892.

31.0

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external conditions, or from the opposite position of those who aver it to have been designedly contrived to meet the special requirements of those conditions, it is a matter for surprise that any should have been found to express a belief that, for distinctness of vision and other purposes for which eyes are required, these specialized and elaborate contrivances are little better than optical failures. Such a notion, if capable of proof, would be a unique exception to that perfect adaptation of means to ends, which, wherever our knowledge is complete, we find everywhere else in nature.

Apart from the question as to whether the nervous structure of an insect's eyes enables it to utilize rays which are beyond the compass of our own, it is clear that the nature of light requires in all organs of vision a structure which is analogous in its optical principles; that is, there must be the means of forming an image, a sensitive screen upon which to receive it, and a connecting line along which the received vibrations may be conveyed to the ulti mate seat of the sensorial impressions. Hence we find a lens, a retina, and an optic nerve to be common to all. We may also infer that the external physical requirements will be approximately the same, so that the vibrations must be of proper quality, they must be of sufficient intensity, and they must impinge upon the retina for a sufficient time to enable its sympathetic fibres to respond to and take up the impulses imparted.

The first difficulty which we meet with in approaching the subject is one which does not apply to insects alone, and therefore does not enter exclusively into present considerations.

In the case of human vision the optic angle is so small that each eye sees the same object, indeed confusion is experienced and a double image is perceived unless the optic axes are so converged upon the object as to bring its image upon the correspondingly sympathetic portions of each retina. But in the case of some animals, and in that of birds, the increase of the optic angle precludes the possibility of such co-ordination, so that an entirely dissimilar picture is presented to each eye, and a further complication is introduced in the case of the chameleon, whose eyes are capable of independent movement in every direction within the limitations of their sockets. We are unable to realize in our own minds what the effect of this may be, because, with the exception of impressions received through the sense of touch, we have no analogous experience, but we may readily conceive it to be a matter of interpretation by which the wide extension of the visual field induces the perception of a panoramic view of the surroundings; and if to eyes which are laterally situated we add also others on the vertex, with divergent axes as we find in the ocelli of many insects, we may further imagine that an extension of the panorama vertically may present a picture embracing an area of more than half a hemisphere.

But when we come to regard vision by means of compound eyes, such as we find in insects, other considerations present themselves and it is obvious that the question as to " why and wherefore" requires another answer. I should like to be allowed here to make a protest against the continued application of the term "facetted" to the corneal surface of the compound eye, as conveying an idea which is not strictly correct. At a recent converzatione I found, amongst other objects exhibited, a plano-convex lense, the curved surface of which was ground off into numerous actual facets, and visitors were invited to look through this from its plane face in order to realize the effect produced by the "facetted" eye of an insect. I need not point out that both structurally and optically this conception was entirely erroneous. The structure of the compound eye is, however, now so well known that I do not propose to enter upon it here at any length, but will merely refer to the recent researches of Professor Exner and others as showing (1) that, contrary to previous speculations, it is capable of forming a distinct image of considerable amplitude, towards which each ocellite contributes its share; (2) that in the picture so produced very many of the pictures formed by adjacent ocellites are either superposed or overlap each other in such a way that the corresponding portions of each become coincident upon the retina; and (3) that it is highly probable that the structure of the organ provides an arrangement which serves a purpose equivalent to that of the iris in the vertebrate eye, with

the further suggestion of a means of focussing. Professor Exner's experiments also prove that by the intervention of the crystalline cones this composite, or "summation," image is erect, and is formed at an increased distance from the corneal surface. Those who have access to the last edition of the late Dr. W. B. Carpenter's book, "The Microscope and its Revelations," will have noticed a reference to these researches, but it may be as well to note that the figure on page 908 appears to have been laterally inverted by the engraver, my own recollection and a rough sketch taken at the time enabling me to say that in the original photograph the letter R was not reversed as shown in the wood cut, and the church faced the other way.

Assuming, therefore, that distinct and otherwise perfect vision is enjoyed by the possessors of compound eyes, it is reasonable to suppose that, if we desire to know what is the raison d'etre of their complex structure, we shall be most likely to find the answer, if we proceed upon lines indicated by the further assumption, that it is required to meet some special necessity arising from conditions of life which differ from those of other creatures.

Pursuing the inquiry in this direction the following considerations make it probable that such conditions may be recognized in connection with the extremely rapid movements of insects in flight.

The angular diameter of the field of distinct vision in the human eye (as distinguished from the visual angle) is much smaller than is commonly supposed, experiment shows that it varies with individuals, but, for present purposes of illustration, we will call it 10°. The inconvenience which would otherwise arise from so circumscribed an area is in practice largely compensated for by the celerity and freedom of motion common to the eyes and head, by virtue of which also we are able to neutralize the effect of our own movements, and, within certain limits, to perceive moving objects which would otherwise cross the field in less time than the minimum required for the production of a distinct retinal image. The exact duration of this period is a matter of personal equation, but may usually be taken as about of a second. Now it is a matter of common experience that when travelling in a railway train at the rate of, say, fives miles an hour, we can, with fixed vision, clearly distinguish the flowers growing adjacent to the track, but, as the speed increases, we become less able to do so, until, at 50 miles an hour, they cross the visual area too rapidly to leave more than an indistinct impression of horizontal lines. It is, however, conceivable that if, as soon as an object had traversed the field of one lens, it came successively within the scope of nine others, which, without break of continuity, would project its image upon the same portion of the retina, the persistence of the image would be increased tenfold, with the obvious result that the flowers would then be seen as clearly whilst passing them at 50 miles per hour as they would be under ordinary circumstances at one-tenth the speed.

If there is truth in this suggestion, that the use of compound eyes is to enable their possessors to enjoy distinct vision during rapid flight, it would appear to derive support from the fact that we find, as a rule, that in larvæ and in insects which are wingless the eyes are either simple, or that the ocellites, of which they are compounded, are comparatively few in number; whilst in those with wings the compound character is developed to its highest degree in genera whose powers of flight are most remarkable. Instances are not wanting in which the eyes of apterous females are simple, whereas they are compound in the case of the winged males of the same species.

That such extremely rapid flyers as the dragon-flies and predatory Diptera are endowed with acute and accurate powers of vision seems to require no further proof than is afforded by the unerring manner in which they strike and capture other insects which are also on the wing.

PROFESSOR SOPHUS RUGE of Dresden, an authority on matters relating to the discovery and exploration of America, pronounces Mr. Winsor's "Columbus" "the most important contribution that North America has made to the present commemoration" of 1492.

TURKISH TIME-PIECES.

BY F. A. SEELY, WASHINGTON, DC.

MANY years ago I ventured the opinion that the development of the mechanical clock was hindered for many centuries by the general use of the Roman system of hours. I am more than ever convinced of this. It is perfectly well known that prior to the Christian era trains of gearing and other mechanical expedients were in use whereby the hand of a clock could be made to travel with uniform motion on a dial. There was, to be sure, no true mechanical escapement, but Ctesibius had devised what I venture to call a water escapement, which, under certain restricted conditions, performed the true function of that element of the modern clock. But the ingenuity of the times was not adequate to the production of the varying movement necessary to keep time in a system in which the length of the hours was constantly changing; and so the clock waited many centuries until the system of hours was changed.

This subject has been brought quite forcibly to my mind by coming into the possession of a number of German and Swiss patents for clocks designed to keep Turkish time.

It appears from the specifications that the Turkish system of hours is practically identical with that of ancient Rome, the day commencing and ending with sunrise, and the middle being at sunset, the two periods of day and night being divided into six hours each, which constantly vary in length with the change of season.

It is obviously impracticable to make up a railroad time-table on such a system, or to accommodate it to numerous other requirements of modern social life; and therefore the wonder is that anybody should think it worth while to construct a clock adapted to this system; but, as the patentees are in all cases residents of Constantinople, it may be inferred that, in devising these clocks, they are endeavoring to minister to a felt want of that capital.

The device employed is of the same character in all the patents, though in some automatic, in others requiring frequent attention. It consists in so adjusting the governing member (pendulum or balance-wheel) as to give it a faster or slower rate from month to month; that is to say, in the winter months, when the period from sunrise to sunset is short, to quicken the action of the movement so that the hand shall pass in proportionately less time over that portion of the dial which represents the hours of daylight than it does in summer, when the days are long. It is obvious at once that this does not accomplish the purpose sought for, and the inference is natural that in the German and Swiss Patent Offices the question of utility cannot have been raised on these applications. If the pendulum is adjusted to a slow beat in the month of June, when the hours from sunrise to sunset are long, it might measure time during the day, but that same slow beat will destroy its capability of measuring off the short hours of the night. A parallel statement is true for the month of December. For this reason these inventions are useless, though they may serve the purpose of the patentees by imposing on the credulous Moslem.

It does not seem impossible in the present state of the arts to construct a time-piece capable of marking off this kind of hours with reasonable precision. The exactness of an astronomical clock or even of an ordinary kitchen clock would be unnecessary. But the inventions above referred to do not approach a solution of the problem, the key to which is to be found in a clock presented to this Government by that of Japan at the close of the Centennial Exposition. In this the hand moves around the dial at a uniform rate throughout the year, the adjustment for different seasons being accomplished by shifting the figures on the dial. It is many years since I have seen this clock, but, as I recollect it, the top of the dial represents sunrise and the bottom sunset, the half-circumference on each side being divided into five hours by a set of figures which can be shifted in place as the seasons change so as to make the day hours long and the night hours short, and vice versa, the sunset hour being shifted also.

I see no great difficulty in producing this shifting of the sunset hour automatically to the right or left as the season may require, nor does it appear to me insurmountable to connect the intermediate hours with the sunset hour so that they shall be shifted proportionately with it. With such a contrivance an hour-hand

moving at an equal rate over the dial would point to the true hour by Turkish time at all seasons of the year, day and night. In fact, the problem seems to me so easy of solution that I can only explain the non-appearance of such clocks in the market by the supposition that no actual demand exists for them.

NOTES UPON THE ACTION OF DRUGS AND AGENCIES UPON THE RESPIRATORY MOVEMENTS.

BY HORATIO C. WOOD, M.D., LL D. (YALE), UNIVERSITY OF PENNSYLVANIA, PHILADELPHIA.

THE results of a research which I have recently completed in the laboratories of the University of Pennsylvania, although bearing very directly upon practical medicine, have. I think, sufficient scientific interest to be noted in the columns of Science.

Hitherto, the study of the action of agencies and drugs upon respiration has been made chiefly, if not solely, by noticing their effects upon the rate of respiratory movements. It is evident, however, that increased activity of rate does not necessarily imply increased activity of function, since the respirations, though more frequently repeated, may be so shallow as to have little effect. Aided by Dr. David Cerna, now of the University of Texas, I have measured the amount of air taken in and out of the lungs of the dog under different conditions.

Emotional or nervous excitement was found to be a most potent agency; the dog seemingly expressing his feelings in his respiration as completely as a human being expresses his in his face; so that during excitement more than twice as much air is moved as during quiet. It has long been known that the dog, having practically no sweat-glands, cools himself through the respiration; and so it was found that heating the animal, by such arrangement of apparatus as not to cause pain, nor to bring hot air in contact with the lungs, nearly doubled the respiratory movement of air. Heat, therefore, is to the dog a powerful respiratory stimulant; when in excess, however, it depresses function, as it was found that if the heating were continued the air movement became almost null. The rapid respiration seen in human beings suffering from fever, indicates that they are affected by heat similarly to the dog.

Chloral was found to be a more positive, persistent, and certain respiratory depressant than the morphine salts; it always reduced the air movement, and the reduction, with repeated and increasing doses of chloral, was progressive, until finally respiration was completely arrested.

The actions of atropine, cocaine, and strychnine were studied both in the normal and in the chloralized dog. Each of these alkaloids was found to be a powerful respiratory stimulant, increasing most markedly the air movement. The rather unexpected result was reached that cocaine is probably the most powerful of the three, but that strychnine is the most persistent and certain in its action. Thus, whilst cocaine seemed to be almost powerless against overwhelming doses of chloral, the influence of strychnine never failed to be manifested.

The bearing of this research upon practical medicine is very evident. During the experimental preparation for my address before the Berlin Medical Congress in 1890, I discovered the great power of strychnine over the respiratory centres when almost completely paralyzed by chloroform or ether; a discovery which led to the universal practical use of strychnine in the treatment of the accidents of anæsthesia. Atropine has long been used in narcotic poisoning, but its value as a respiratory stimulant within the last year or two has been very seriously challenged. Our research, however, re-demonstrated its power as a respiratory stimulant. Cocaine has been used to some extent as a respiratory stimulant, but it seems to be much more efficacious than is gen erally thought. It was found in our research that in the deeply chloralized dog, after respiration had been brought up as far as possible by one respiratory stimulant, the second stimulant was able to still further increase the extent and power of the respiratory movements. I have apparently saved human life in respiratory failure, by adding cocaine to the strychnine which was being given in as large dose as was thought justifiable. Cocaine

and strychnine, however, have so much similarity of action upon the spinal cord that the use of one of them would probably somewhat increase any danger that may have been incurred by the administration of large doses of the other.

On the other hand, atropine has little influence upon the spinal cord, its general physiological action being quite distinct from that of cocaine or strychnine. It is therefore probable that by the consentaneous use of atropine and strychnine, or of atropine and cocaine, the physician may obtain the advantage of what, many years ago, I spoke of as the "crossed action" of drugs; the two drugs touching and reinforcing one another in their influence upon the respiratory functions, and spreading wide apart from each other in their unwished for and deletereous effects.

In conclusion, for the sake of any one who may be interested in the details of this research, it may be stated that it will shortly be published in full in the English Journal of Physiology.

LETTERS TO THE EDITOR.

Correspondents are requested to be as brief as possible. The writer's nume is in all cases required as proof of good faith.

On request in advance, one hundred copies of the number containing his communication will be furnished free to any correspondent.

The editor will be glad to publish any queries consonant with the character of the journal.

Man and the Glacial Period.

A MISLEADING paragraph in Dr. Brinton's otherwise excellent review of a recent publication under the above caption,1 in con⚫nection with the Reverend Professor Wright's response,' seems to demand a further word. Dr. Brinton errs in saying "As a glacialist, the author of this volume stands among the first in the country, and his long study of that remarkable period in the geologic history of our planet invests everything he says about it with uncommon authority."

Within recent years there has grown up a new branch of geologic science, which has been called by its devotees "geomorphic geology," "geomorphology," and still more acceptably "geomorphy," and which is frequently spoken of as the "New Geology." It is the function of geomorphy to read geologic history from earth-forms, as the older geology read history from deposits and their fossils. Beginning a score of years ago with Powell's conception of the "base-level," at which erosion ceases, the primary idea has extended and expanded until now the geologist not only recognizes ancient base-levels in certain topographic forms, but is able to determine from steepness of slopes and other topographic relations the rate at which erosion has proceeded in the past, and thereby the attitude and altitude of the land during earlier ages. This branch of science has been successfully pursued by a number of geologists in this country and a few abroad, and is taught in three or four universities; and it has been found of especial use in the study of glacial deposits It is, however, a sealed book to Professor Wright; not a syllable in his latest work, or in any other of his many publications, or in his public utterances before scientific societies, suggests that he is aware of the existence of the New Geology.

Within two decades the discriminating genius of Chamberlin and a score of fellow-workers in this country has thrown much light on the events and episodes of the glacial period. Largely through the application of geomorphy, it has been shown that the glacial deposits of north-eastern America represent two, three, or more distinct ice invasions occurring at different epochs in a long period, and that the earliest of these deposits is many times older than the latest - indeed the leading authorities agree that if the post-glacial period be represented by unity, then the entire glacial period must be represented by two figures. This succession of ice deposits and ice invasions is not, indeed, recognized by some of those glacialists whose observations have been confined to regions in which only a single deposit is represented; but with one or two exceptions (including our author's namesake, A. A. Wright, professor of geology at Oberlin) every geologist who has studied the 1 Science, vol. xx., 1892, p. 249.

2 Op. cit., pp. 275-277.

marginal drift holds to the bipartite or tripartite or multipartite character of glacial deposits and glacial history. This succession is not admitted by the Reverend Professor Wright. Accordingly, his ideas concerning early man have no definite time-basis and cannot be discussed intelligently by modern archæologists — it would be as easy to discuss the opinions of an author who confounded not only all the successive dynasties recorded in the monuments and hieroglyphs of Egypt but also the works of the modern fellahin, or of a genealogist who argued that the families of a dozen successive generations dined together at the same board. As an exposition of the antiquity of man and the glacial theory, "Man and the Glacial Period" is a cry from the tombs of a dead past; it represents the primitive knowledge of a quartercentury ago, and might then have been considered authoritative; but its publication to-day is an offense to science.

Professor Wright objects to Dr. Brinton's "flippant treatment" of the Nampa figurine, and insists that a geologist who happened to detect the fraud on the ground should burden scientific literature with some detailed statement. It does not seem to occur to him that the gentleman in question avoided rushing into print simply because the fraud was too transparent to deceive geologists, who alone are competent to deal with questions concerning the geologic antiquity of man. Respectable and cultured gentlemen seem indeed to have been deceived by this alleged "find," — but they were not geologists; so, too, respectable and cultured people, including an illustrious naturalist, have been deluded by a Philadelphia adventurer with an alleged motor,but no physicist was deceived; in like manner, intelligent and honest people have been deluded by a brazen pretender into the belief that the heavens may be frightened into tears by cannonading but the meteorologists are not deluded; and the circlesquares and perpetual-motion inventors are abroad in the land, yet the mathematicians and the mechanicians are not deceived. And it would be folly for the physicist, the meteorologist, the mathematician, and the mechanician to rush into print and advertise each new fraud, for thereby the press would be flooded and libraries crowded, while fraud would only flourish the more for the advertising. So long as poor human nature remains as it is, the knave and the dupe we shall always have with us; and it is to be regretted that a presumably competent authority in his own specialty of theology should be willing to assume either role in another line of activity.

The author of the work has indeed visited many existing glaciers, and his observations would be of value to geologists if they could be accepted with confidence. A case in point is his measurement of the rate of flow in Muir glacier, in which he employed primitive methods and recorded a result so extraordinary as to challenge credulity. Subsequently, the measurement was repeated by Professor Reid by a superior method, with a widely different result which is in harmony with all other observations. Instead of acknowledging his evident blunder, or even passing over the matter in silence, Professor Wright has the assurance to "talk round" the issue (p. 47), and thereby impugns the excellent work of a later observer.

"Man and the Glacial Period" is published by a reputable house as one of an "International Scientific Series," and thereby acquires a respectability to which otherwise it could not aspire. Dr. Brinton has fairly, albeit charitably, shown its weakness from the standpoint of anthropology; other reviewers have shown that it sinks even lower when viewed from the standpoint of geology. In other ways, too, the title page conveys erroneous impressions as to the profession and standing of the author. Thus, he takes unto himself the title "Assistant on the United States Geological Survey." The facts are, that he was temporarily employed by one of the collaborators of the bureau largely for the purpose of testing his competence as an observer; and that the test resulted unsatisfactorily to the bureau and was brought to an end several years ago.

In brief, the world would be wiser if the book were not written. W. J. MCGEE.

Washington, D.C.

3 E g., Professor T. C. Chamberlin in The Dial, Vol. XIII., pp. 303-306, November 16, 1892.

Pseudaurora Borealis; or, What was It?

THE observations which I am about to recount may not be new to others, but, as I have failed to see or hear of any such after several years' waiting, I communicate mine, hoping that by doing so I may call them out if there are any. The business portions of Minneapolis, Minn., had for many years been lighted by the Brush system of electricity, during which time that method of street illumination had been extended considerably in all directions, leaving, however, much more that continued to be lighted by gas and oil. I had occasion to visit the suburbs of the city under circumstances which delayed my return until a very late hour, and for a considerable portion of my way the latter method of lighting prevailed. On passing into the electrically-lighted section, my attention was arrested by the appearance of the aurora borealis, or northern lights.

It being in the month of February, and their appearance at that season by no means a rare event, while the lateness of the hour, and the severity of the cold, with the air so filled with frost as to give an appearance of a light fog, I was hastening forward as rapidly as I could on foot, when I noticed that the aurora had disappeared, but after a few steps more it reappeared. Pausing a moment, I saw there was no mistaking the fact of my seeing a genuine display of northern lights, I again went forward with the same experience of interruption. This circumstance awakened a suspicion that the phenomena were in some way to be accounted for by the presence of the electric lights, and, after another brief pause to make myself assured of the certainty of my observations, I went back along the way I had come until fully out of the zone of the Brush lights, and well into that of the gas-lamps, where I found no signs of an aurora.

Returning slowly towards and into the former illumination, all of the observations were repeated precisely as at first, until having passed a given burner, when the phenomena again ceased. After repeatedly changing my position in relation to a special burner in a northern and southern direction, during which I discovered that the phenomena was most distinct when I was observing them at or about the angle of 60° to the burner, a corresponding movement east and west gave no more facts, and after once more noting the characteristic movements of the serrated columns of partially prismatic radiations of the auroral beams along the penumbrated arc, I went on my way resolved to keep a good outlook for another such observation, but it has never come after nearly five years of waiting. If others have noticed the same, or similar phenomena, it will be gratifying, and in order, for them to say so. Anacortes, Washington, Nov. 3.

P. L. NATCH, M.D.

few instances I have seen humming-birds perch upon the bark below the holes in order to drink long without being forced to keep their wings moving while enjoying the sweet sap.

In some cases I have placed small birch-bark cups upon trees frequented by the sap-suckers and their guests, and in each such instance the humming-birds have been as quick as the woodpeckers to discover the diluted maple syrup with which the cups were filled, and to drink it in considerable quantities. I remember seeing one drink for sixty seconds, with a ten seconds' rest in the middle of the minute.

Most of the orchards" at which I have seen humming-birds as visitors from year to year have been composed of red maples or gray birches. At one of the birch orchards I shot two humming-birds, a male and a female, in order to ascertain whether more of their kind were visiting the holes. Only nine minutes elapsed before another was at the holes drinking. FRANK BOLLES.

Cambridge, Nov. 28.

Sense of Direction.

SOME time in the fifties, in Oregon, a party of prospectors took a mule team, wagon, and camping equipage on a prospecting tour. In order to be correct in their local geography, and to retrace their steps should they find anything worthy of a re-visit, they took a civil engineer along, who took the bearing of every course and the distance was chained.

When they gave up the prospecting enterprise, their route had been so tortuous that they decided to take the direct route for the home camp. The engineer footed up the latitudes and departures

of the courses run, and made a calculation of the course home, and all struck for the home camp. When they reached the end of their course, night had overtaken them, and they found themselves, not in the home camp, but in the woods, with no objects or land-marks that any of the party could recognize.

As the engineer took no "back-sights," or check bearings, he said that local attraction somewhere in their journey had thrown him off a little and that they were in the neighborhood of the home camp. At this, the driver turned one of his mules loose, which went directly to the camp, about three-quarters of a mile distant. As the mules were not allowed to run at large, for fear of wandering off or being stolen by Indians, this mule had never before been over that route, and must have had a sense of direction. It was a joke on the engineer which he did not relish, though it had great staying qualities. "

Rockville, Ind., Nov. 14.

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JOHN T. CAMPBELL.

The Humming-Bird's Food.

FOR three years I have made a special study of the habits of the yellow-bellied, or sap-sucking woodpecker (Sphyrapicus varius), as found in the White Mountains of New Hampshire. The birds arrive in that region near the middle or 20th of April, and remain until about the middle of October. During the whole of this period they derive the more important part of their food-supply from sap-yielding holes which they drill through the bark of red maples, red oaks, poplars, white and gray birches, the white ash and some other trees and shrubs. In every instance where I have found a well-marked drinking-place established by the sap-suckers, humming-birds have been regular attendants upon it during the summer months.

I have paid hundreds of visits to these "orchards" of the sapsuckers, and have watched them for many hours at a time. By so doing I have ascertained that, as a rule, one individual humming-bird seems to acquire a sort of easement in the sap-fountains of the woodpeckers, and if another ruby-throat attempts to drink sap at his spring, violent resistance is offered.

The humming birds, at "orchards" where they are not molested by the woodpeckers, drink scores of times in the course of the long summer day. When not drinking they are usually perched on twigs a few yards from the holes, keeping their nervous heads wagging from side to side while watching for intruders.

In a

Electrical Phenomena on the Mountains of Colorado. IN Science for Sept. 23, Mr. O. C. Chariton describes a mountain experience, and inquires if it is common or dangerous.

The peculiar buzzing and crackling sound, the standing of the hair on end, etc., are extremely common on the mountains of Colorado. The prospectors, miners, and drivers of pack trains to the high mines (above 11,000 feet) live in the midst of these electrical phenomena, and often find much amusement in observing their effect on the average "tenderfoot," especially when lady tourists, as not seldom happens, find their long hair slip from the fastenings and stand up like the fabled head-dress of the Furies. I have repeatedly heard the sounds at elevations between 6,000 and 7,000 feet, but they are much more noticeable at higher elevations, where they are sometimes terrific. They sometimes mark the tension of the air just preceding a discharge of lightning, but in general they are harmless. I have many times noticed them proceeding with hardly any interruption while the lightning was leaping from cloud to cloud overhead. They are caused by the passage of an electrified cloud, and the effect is rather worse when one is in the midst of the cloud. On these mountains the manifestation of intense electrical phenomena is seldom seen except when there is hail or pellet snow, or the most violent summer showers; and the latter usually have hail in some part of the The loudest buzzings I have ever heard came while a

storm.

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