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ing rain, it follows, from a great number of observations, that the on two circular springs D. These springs, pressing upwards, act indications of this instrument are then extremely probable. As upon the lever p, and oppose the pressure on the part 2. Now, to the sudden variations, either in the one direction or in the other, suppose that the atmospheric pressure increases, the top m is they indicate bad or stormy weather. If to these considerations pressed down, the lever p is lowered and transmits its motion by be added the observations on the direction of the winds and the the piece K to the lever B, and to the plate A which presses on the temperature of the air, indications may be drawn from the baro- | springs D. But this plate carries an arm which rests on a rod E; meter, which are very useful for agricultural purposes. But it and this rod by means of a bent lever H, communicates the motion must be remarked that the table showing the relation between to a chain o wound on the axis of an index c; and thus the chain the height of the column and the state of the weather is the result conveys its motion to the index. Under the index is fixed a dial, of old and numerous observations in some particular locality; and fig. 78, which is experimentally graduated so that its indications that it is not adapted for every country in the world, or even for may agree with the barometers of MM. Fontin and Gay-Lussac. every place in the same country. In every country, the indica- The aneroïd barometer is very sensible and very portable; but tions of the barometer are greatly modified by the geographical the number of pieces in it is very considerable. When we come position of the place, and this must always be taken into account to treat of the manometer, a barometer of new construction, and in the accurate construction of such instruments.

without mercury, will fall under our notice. The Wheel Barometer, or Weather Glass ---As an elegant piece As the barometers we have described are chiefly of French conof household furniture, and not as a philosophical instrument, the struction, the scales in our engravings have been marked with the whcel barometer is specially intended to indicate good or bad initials of the words used by the makers of these instruments, and weather! It is sometimes called the dial barometer, because it is with their graduations in millimetres, a millimetre being •039371 furnished with a dial and index like a clock, see fig. 76. This of an inch, or very nearly one-twenty-fifth part of an inch. instrument is merely a siphon barometer furnished with a Accordingly, we give below a table of the initials engraven on mechanism which is put in motion by the rising and falling of the these instruments, the French words for which they stand, and mercury, see fig. 76.

the corresponding English words; the number of millimetres

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In this mechanism a pulley o is fastened to the axis of the on their scales, and the corresponding number of English index, and over this pulley a cord passes, carrying a weight P at inches. ore extremity and at the other extremity an iron float, a little

. heavier than the weight; this float rests on the mercury in the Initials. French Names. English Names. Millimetres. English in. smaller branch of the barometric tube. If the atmospheric pres- T. Tempete, Stormy;


28.78 sure increases, the level of the mercury falls in this branch, and

G. P.

Grande pluie, Very rainy; 740 the float descends and moves the pulley and the index from left to P. Pluie, ou vent, Rainy, or windy; 749 right. The contrary motion takes place when the pressure V.


Changeable; 758 diminishes, because then the mercury rises in the smaller branch B. T.

Beau temps,

Fair Weather; 767 of the tube, and causes the float to rise with it. If the instru- B.F. Beau fixe,

Settled fair; 776

30:55 ment has heeu carefully constructed, the index will point to the T. S.

Very dry; 785 words changeable, rainy, fair weather, &c. when the barometer takes the heights corresponding to these indications; but this is

Measurement of Heights by the Barometer --The pressure of the 90 seldom the case in the instruments brought to the market, atmosphere decreasing in proportion to the elevation of the place that they can only be looked upon as pretty philosophical to which the barometer is taken, the height of the barometer .

follows the game law, and thus it becomes an instrument for

deterinining the altitudes of mountains. It was, in fact, soon The Aneroid Barometer.-A new kind of barometer, in which observed that when the altitudes of the places of, observation no mercury is employed, has attracted notice for some years past, increased in arithmetical progression, the densities or pressures known under the name of the aneroïd barometer (from the Greek, of the atmosphere decreased in a geometrical progression. The signifying a Liquidless Barometer). This instrument is constructed following approximate table of the densities of the air at different by M. Vidi of Paris

, and was originally suggested by M. Conté, heights above the surface of the earth, will give some idea of this a learned inember of the French expedition into Egypt. The principle. parts of this instrument are shown in fig. 77, and in fig. 78; the


Dercitat. whole is represented as enclosed in a case with a dial, its diameter

I being only about 3} inches. The principal part of this barometer is a cylindric,reservoir M, made of brass, and having the top very

37 miles thin and flexible. A vacuum is made in this reservoir, so that

7 the atmospheric pressure tends always to push in the top part M.

101 But upon this top'are fixed two uprights 8, which, by means of a eonnecting bar, press on a lever p, intended to balance the pressure


3 upon M. For this purpose, this lever is fixed to a bar k, which


&c. oscillates freely on two pivots placed at its extremities. By means of a lover B, this bar K is connected with a plate A, which presses It has been remarked that, according to this approximation

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to the law of progression in the density, or rather in the rarity of speaking, however, this acid seldom comes before the notice of the the atmosphere, exhibited in this table, it might be shown that a chemist; moreover its compounds are characterised by their difcubic inch of the air we breathe at the surface of the earth, would, ficult solubility, hence it may be considered as "hors de combat," at the height of 500 miles above it, fill a sphere equal in diameter Applying the facts just deduced, remembering that the grand to the orbit of Saturn; that is, on the supposition that the power combustion-supporting function is strongly developed in chlorate of expansion in the air were not counteracted by intense refrige- of potash--remembering that nitrate of potash (nitre) is a conration, or by the action of gravity on its attenuated particles. gener of the former, and that it is an essential component of gun

For measuring the heights of mountains by the barometer, powder-you will now know, if you did not know before, the reason Laplace has given a formula, which was modified by M. Biot into why gunpowder burns when ranned into a gun from which all the the following:

atmospheric air is excluded. Gunpowder carries within itself 2(+)

combustibles-charcoal and sulphur, and a supporter of combustion, D=60346 (1 +.002837 cos )


oxygen (in ihe nitre) hence it is totally independent of the aid

of atmospheric air. Many gunsmiths are so ignorant of chemistry, in which denotes the vertical distance, in English feet, between that tbey are not aware of the true conditions under which gunthe two places whose difference of level is required; H, the height powder burns. You may sometimes see a little hole drilled in the of the barometer at the lower station, and h the height at the side of a gun breech, the use of which, gunmakers will tell you, upper station ; T and t denote the corresponding temperatures of is to let in the air and promote the burning of the powder. This the air on the centigrade thermometer, at the stations respectively; | is simply ridiculous. and o, denotes the latitude of the place.

In the first place, the powder does not want air; in the second M. Oltmans has constructed tables by means of which this place, through this hole no air could enter, seeing that the expanformula can be easily calculated in metres; the only difference sive force of the inflamed gunpowder is outwards. This little being in the factor 60346 feet, which in the original formula is hole facilitates the loading of guns-rifles especially, -and facili18393 metres. These tables, with the manner of using them, are tates also the escape of foul air or vapours: beyond this it is of no to be found in the “Annuaires des Bureau des Longitudes.” service whatever. The student will find a similar formula with an example worked, Seeing that nitre is a congener of chlorate of potash, you may in "Miller's: Hydrostatics." If the altitude to be determined by perhaps ask whether it might be used instead of the chlorate für the barometer be uot very great, one observer alone can perform the purpose of yielding oxygen gas. Yes; it sometimes (unmixed the experiment; but if the altitude be very considerable, and with oxide of manganese) is used for this purpose; but yielding requires a long time between the observations in order to complete up its gas with greater ditficulty, it is less efficient. You perhaps the ascent, the pressure of the atmosphere may vary, and it will also ask, whether the chlorate might not be used instead of nitre then be necessary to have two good barometers. One of the as a constituent of gunpowder ? Theoretically I might answer observers with one barometer then remains at the foot of the Yes; but practically, No. Gunpowder made vith chlorate of potash mountain, while the other observer ascends to the top with the is far too explosire for safety. Not only would there be danger other. At a given hour, each obserres his own barometer, and of explosion from the act of ramming, but the danger attendant on thus the true height of the column at each place, the true differ- the manufacture of such guapowder on a large scale would be ence of the columns, and consequently the true difference of level frightful. The French tried the manufacture during the wars of between the places are accurately obtained.

the great revolution, and are even said to bave used chlorate gunpowder in one of their campaigos; but the frequent explosions which occurred at the powder-mills led to the final abandonment

of the process. LESSONS IN CHEMISTRY.-No. XVII. A very simple, though indirect, method of demonstrating ting

facility with which chlorate of potash evolves its oxygen is as RESUMING our consideration of oxygen, I shall require you to follows. Punder two or three grains of the substance separately, arrange the generating apparatus as before; and this being done, and an equal oreight of brimstone separately; incorporate these on to fill several eight ounce, or ounce and a half, bottles full of the a piece of paper, by means of a feather or other soft body; wrap gas. We will proceed to use this gas very speedily. I wish, the mixture in a piece of paper, plan: the envelop on an ånyil or however, before doing so, to direct your attention to certain other hard sui face, and strike it sill i.:19 with a hammer. The properties of chlorate of potash dependent upon the oxygen it whole explodes with a vivient r:!: Occasionally the expericontains.

ment is varied by rubbing a few grains of chlorate of potash and The most prominent characteristic of oxygen, as you are now

an equal quantity of sulphur sharply together in a mortar, by a aware, is its property of supporting combustion; the idea would series of sharp short strokes, or rather downward pushes, half seem likely enough, then, that a substance containing so much stroke, half blow, when a series of explosions results. When per

up We shall see.

but the result of its combustion was found to be so destructive to Dissolve some chlorate of potash in water; dip into the solution the lock, that its employment was soon abandoned in favour of a piece of paper (blotting-paper is best); dry the paper, and bring the so-called anti-corrosive caps, in which fulminating mercury it into contact with flame or a red-hot coal. I do not wish the takes the place of chlorate of potash and sulphur. We will noy paper itself to burst into flame, but the contrary; if therefore this return to the consideration of gasewus oxygen. should occur, blow out the flame, leaving a mere ignited paper If oxygen gas be so powerful a supporter of wood and other ordiedge. Remark now how curiously the ignition traverses the nary combustibles, the supposition would appear likely, from a paper, which no longer burns as common paper. I dare say you priori reasoning, that bodics incombustible in atmospherio air, or will recognise something like this phenomenon. You will say it imperfectly combustible, should readily burn in this gas. I do burns like touch-paper. Touch-paper indeed it is, of the best qua- not know whether you will be surprised to be informed that iron, lity; far better than you could have made with the ordinary agent and indeed all metals without exception, are combustible. As -saltpetre; and now you may remember the following important regards iron, you have often, I doubt not, witnessed its combusfact: that " any substance capable of making touch-paper mast con- tion when heated to whiteness in a smith's forge and rapidly tain an acid which holds five atoms of oxygen." Therefore, know- withdrawn, though probably you failed to reason on the bearings ing this rule, it follows that chlorate of potash, if placed before of the phenomenon. We will now show how exceedingly comyou as an unknown substance for examination, would at once have bustible is iron in oxygen gas. There is an old-established been determined as containing one out of four acids.

conventional-a" lectuning" method of performing the combus

tion of iron in oxygen gas, which I will describe further on. It Nitric

is well adapted for display in lecture-rooms and generally on the Chloric acids

large scale ; but it is not the best adapted to the requirements of Bromic

our little bottles. Iodic

I shall modify the experiment as follows. Take a circular dise Straining a point, we might admit a fifth acid, the “perchloric," of tin plate, fig. 1, large enough to cover the mouth of your oxygen containing no less than seven equivalents of oxygen; practically bottle, and perforate this pipe centrally with a little bole, just


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large enough to admit a needle tightly; finally, stick the eye

end EXPERIMENT. For the performance of the succeeding exof the needle in a cork, so that an arrangement may result as fol- periment we shall require, in addition to the glass jar or bottle, lows; finally, dip the extreme point of the needle in melted brim- cork, and metallic disc, already described, the following little instrum stone, and this part of our arrangement is complete.

ment, fig. 7, being a small copper ladle, secured by rivetting---not Fig. 1. Fig. 2.

Fig. 7.

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soldering—at the point marked l. These instruments are termed

by chemists cleflagrating ladles, and serve the purpose of exposing Now proceed as follows. Ignite the brimstone at the point of to the action of gases, liquids or fusible solids. We shall require the needle, and plunge the latter into a bottle containing oxygen two of these ladies; one for the purpose of igniting sulphur, the gas, fig. 2.' Theneedle will burn vividly, throwing off sparks in other for the purpose of igniting phosphorus, in oxygen gas. all directions, some of which, in all probability, will stick in the

Igrition of Sulphur.-Having put a little sulphur into one glass, partially fusing it. I repeat that the mode of operation here described is not the manner already described, ignite the sulphur by heating it in the

ofmthese deflagrating ladles, attached to a cork and disc in the most elegant, but it is the best adapted to the necessities of our fame of a spirit-lamp. When thoroughly ignited, dip it into a present apparatus. The usual method of performing the experi- jár or bottle containing oxògen. Remark the character of comment is by employing, as the gas receiver,, a jar of this kind, bustion--the pale blue lambent flame, the small amount of light, placed to stand in a plate containing water, and covered with a the gaseous nature of the result of combustion. When the sulglass pane, fig. 3; using a helical or corkscrew-formed wire of this phur has ceased to burn, cover the receiver or bottle with a glass kind, fig. 4. If you can procure some of these gasijars, well and pane, and put it aside.

EXPERIENT.-- Combustion of Phosphorus in Oxygen Gas.Fig. 3.

Fig. 4.

I am about to mention certain details connected with the performance of this experiment, and you must attend to them implicitly, otherwise your experiment will fail, and yourself, most likely, will be severely burned. Pour a lump of phosphorus from the water in which you will purchase it, iuto a plate of water; cut off a very little lump (not bigger than a pepper-corn) under water ; remove the piece thus cat off, not with the finger and thumb; but a pair of tweezers, scissors, or something of that sort; dry it by contact with blotting paper; put it into a defiagrating ladle; ignite it by contact of a hot wire applied to its surface, not by a flame applied underneath the ladle; plunge it into a bottle or a jar containing oxygen, and remark every peculiarity of the combustion which ensues. Preserve the results of this combustion, as you have preserved the others. The examination of all these products shall be the subject of our next lesson.



Fig. 5.

good, you may employ them in performing the experiments about to be detailed; if not, you must be content to use large-mouthed bottles.

LESSONS IN GEOLOGY._No. XLIX. EXPERIMENT.–Bore a hole through a piece of charcoal ; dass through the hole a wire; bend the wire into á sort of knot Bỉ Thos. W. JENKYN, D.D., F.R.G.S., F.G.S., &c. underneath, and attach it above to a tin-plate disc and cork, as

CHAPTER V. représented in fig. 5. Ignite the charcoal ; plunge it into the jar or bótti'e, fig. 6; wait until the combustion has ceased; then secure the

ON THE CLASSIFICATION OF ROCKS. mouth of the jar or bottle with a glass pane. The charcoal will

Fig, 6.

The rocks which contain fossils, and which on that account are
distinguished by the name of fossiliferous rocks, have been
divided by geologists, generally, into three series: The lowest
contain the most ancient forings of animal existence, and
are therefore called pålæozoic (from raadiós, palaids, old,
and lwn, zoé, life), that is, old-life rochi: The series rest-
ing upon the palæozoic are called secondary rocks, or
mesozoic (from usos; mesos, middle, and twn, zoé, life), ,
that is, middle-life rocks. The series resting on the mesozoic
are called the tertiaries, ho called because their beds contain a
third form of organic life. In the lowest and in the middle series,
all the imbedded fossils are remains of animals altogether extinct.
In the third series, or the tertiaries, the lowest group of rocks

contains some extinct species and a few of existing species; a burn with extraordinary splendour, and the sole result of com- higher group contains less extinct species and more of the present bustion vill hereafter be found to be a gt, invisible like oxygen, race; and in the highest group, there are extremely few of the but totally dissimilar to it in every other characteristic.

ancient 'speefes, and à vast majority of the species which cow fites On these accounts, the tertiary series, according to the comparative 1. PEAT Boos. Peat moster are we known in all the mounamounts of extinct and existing fossils which they contain, bare tainous districts of the north of Europe and America. They are been called Eocene, Meiocene; and Pleiocene; terms wbieh will divided into two distinct classes : first, immersed formations probe explained in our next lesson. All the 'tertiary beds contain duced by the accumulation of aquatic plants, such as reeds, sedges, fossils of the present race of animals; but the group called the &c.; and secondly, the emerged formations, caused principally by Newer Pleiocene by some, and Pleistocene by others, contains so the growth and decay of the plant called sphagnum. Some much as 95 per cent of the present species, and is therefore called peat mosses lie frequently in highly inclined planes. Near Kiel, in a rock of MODERN formation:


Northern Germany, vast beds of peat show the two formations But, in the order of superposition, there are series of rocks much superimposed, where the peat bas first grown in a basin or hollow higher and newer in geological sequence than the Pleistocene several feet deep, and when it has reached the surface of the beds; rocks which are characterised by having all their fossil water, the emerged formation has commenced. A third mode of shells identical with the species that are now living. It is this peat growth has been observed in the Vosges, and in Denmark, fact that distinguishes the lowest of these beds from the newer where, in deep, but small basins, the peat-forming plants have pleiocene, or rather the pleistocene, whose deposits always contain begun to grow at the surface of the water, and the basin has some proportion of an extinct species. It has hitherto been found become gradually filled by the immersion of the floating turf, and difficult to coin a term or a phrase that shall properly and fully this continually thickened by the growth of new plants. express the geological characteristics of these later groups of You may easily think that such abysses, concealed by verdure, rocks. Some have called then Post Tertiary, others Post Pleiocene, have often proved dangerous to travellers and to cattle. These and some continental geologists have tried to introduce the name basins are filled with numerous bones and instruments of various Quaternary, or the fourth series, a term which seems as admis- kinds, both ancient and modern, which give a clue to the different sible as the word tertiary for the underlying rocks; and in some epochs in their forination. works they are called RECENT formations.

2. DELTAS OF RIVERS. The streams and brooks which issue
It will answer all the purposes of this lesson, if we agree to from mountain sides are all charged with eartby particles, which
designate all the beds which contain the fossil remains of the they deposit in the beds of rivers as mud, gravel, and pebbles, and
existing races of plants and animals, by the term POST PLEISTO- thus gradually form allurial plains. If the force of streams be
cene rocks. This class of modern rocks comprehend not only strong, the current transports an immense quantity of detritus to
those strata which can be proved to have originated since the the mouths of rivers, where they form the accumulations of silt
creation of man, but also sedimentary beds of much greater and sand, called deltas. In these deltas are imbedded the leaves
extent and thickness, which contain no signs of man or his works, of plunts, branches of trees, remains of animals, shells of fish,
but enclose remains of species of animals identical with races human bones, and works of art. Specimens of such formations
now living. It is true that in some of the lower beds of eren are supplied by some of our rivers in England, especially the
these modern rocks we find the bones of ancient quadrupeds, such Mersey, the Dee, the Severn, and the Thames; but they are pre-
as the mammoth, the mastodon, the megatherium, &c., species sented on a large scale by such rivers as the Nile of Egypt, the
that probably never co-existed with the human race; nevertheless Ganges in India, and the Mississipi in North America.
the stells that are found fossil in these beds are the same as those To constilute a series of deposits a post pleistocene group,
of testacea now living.

it is not necessary that they should always be found superim-
posed upon the Tertiaries, for sometimes they may be found
resting on the most ancient rocks. In the annexed diagram,

a a represents rocks of the greatest antiquity, and d the ante-
Submarine Deposits.

historical deposits; ¢, the rocks formed since the creation of Deltas of Rivers. 1. The present period Coral Reefs.

man, and b rocks that are now in the process of formation.
Deposits in Lakes.-Salt.
Rocks now forining.

Peat Mosses.
Beds of Lava, and Volcanic Cones.
Sand Dunes.




the creation of the


Raised Beaches.

d 2. The historical

Shell Mari.
period, or
Rocks formed since
Submerged Forests.

Fig. 1. Recent Deposits Kesting repon Ancient Rouks.
Deposits in Caverns.
the creation of man.
Beds of human remains.

3. SUBMARINE Deposits. You have already seen in the lessons
9. The ante-historical
Loess of the Rhine.

on the agency of running water, that rivers which deposit their period, or Regur or bottom soil of India.

gravel and sand in deltes, carry their finest particles far into the Rocks formed since The Till.

bosom of the sea, wheto, after having been transported by currents The Newer part of the Boulder forma. and agitated by the waves, they finally sütile dúin as a sediment present races of tion with Erratics.

on the deep and quict floor of the ocean. Colonel Sabine, in his plants and aninals.

calculations on tlie sedínuents carried down by the river Amazon N. B. In the rocks of this ante-historical heriod, all the fossil in South America, has shown that strata are now forming in shells are' of the species now living; they are destitute of regular deposits over great spaces of the bed of the ocean.

The human remains; and the bones of quadrupeds imbedded in system of DREDGING carried on by scientific men, uniformly shows them are partly of extinct species.

that the strata which are yow deposited in the bed of the sea, are It is right to say that you will not find this distribution of the pebbly where the waters are much agitated, sandy where the post pleistocene rocks, either by name or by arrangement, in any agitation is moderate, and argillarious or clayey where the waters work on Geology, and that it is made solely to facilitate your

are comparatively quiet.

Besides these rocks deposited neobanically in the sea by rivers, progress in the knowledge of this particular forination. This series is divided into three groups of rocks, piz, rocks that are formation by the remicsl ayeury of ite calcareous, siliceous and

it is well known that there are many beds now in the course cr now in the process of formation ; rocks that have been forned ferrugiavus matter which is swepi hy rivers into the ocean. since the existence of man; and rocks that have been deposited the niouth of the Rhone in the Sonth of France, calcareous beds since the creation of the present race of plants and animals.

are now fornring in the Mediterraneanl. On the shores of the Red I. ROCKS NOW IN THE COURSE OF FORMATION.

Sea a rock forination is now in progress, composed of sand, gravel,

corallives, fragitents of older rock., werd, pottery, and bits of Your attention has been already directed to the rocles that are wood wåshed up by the dra and tencnted trigetber by carbonate now in the process of formations in the lessons which have been of lime slightly coloured by oxide of iron. given on the reproductive Agency vf fire, water, and wind, as 4. THE GROWTH UP TORAT, Hecks. The host modern instance agents of change in the crust of the earth. You are therefore of the fortration vf tural rocks is found in the Bermudes, and the prepared for the statement that rocks are being formed in our own Bahatimas. The coral reef in these disti-icts consists of masses day.

of numerous species of madrepores, astræa, and several others,




growing confusedly together, without any other apparent British Museum an indisputable specimen of a human skeleton, order than that of accidental succession and aggregation both found imbedded in a rock of solid limestone formed on the shores upwards and sidewards. In the cavities of the mass are found of Guadaloupe. This rock can be proved not to belong to the fragments of corals, shells and other organic remains, perfect or class of ancient limestones, but to be a very recent alluvial formabroken, sand and chalky mud, and the whole becomes solidified tion; for it contains, besides shells of the present sea, fossil into a compact rock by the aid of calcareous cement, while the arrows, stone hatchets, and pieces of rude pottery. A battle upward growth of the living coral, and the accumulation of loose between the Caribs and the Gallibis took place on that spot in material on the surface proceed at the same time together. The 1710, and there is every probability that this is a skeleton of one coral work is ever in progress until it reaches the surface of the of the slain, either buried there, or sunken and imbedded when

The loose materials are either dispersed through the the coralline mass was soft. crevices and inside of the reef, which thus pack and cement it The circumstance that has occasioned the greatest perplexity to together, or else they are carried landward or seaward to form the geologists is, that some signs of human contrivances, and even compact bases of other formations.

human bones, have been found in caverns, mingled with the bones 5. SALT FORMATIONS. Very little is known of the origin of of animals that are certainly extinct as to those districts, if not rock salt, and geologists have not been able to decide whether the absolutely extinct as to the globe at large. As far, therefore, as precipitation of salt is owing to evaporation, or not. It seems mere geological evidence is concerned, it would be unsafe to say clear that, in the basins of lagoons, lakes, or inland seas, pure that man has not been ai inhabitant of the earth for a much salt can be formed only in the central parts of such basins, parts longer time than modern chronologists assert. As to the human where no earthy sediment could be brought by currents, and bones which have been found mixed with those of extinct animals where no sand could be drifted by winds. We cannot say what in certain caverns of Belgium and France, all of which seem to chemical processes are now going on in the quiet depths of the have been deposited at the same time during the formation of the Mediterranean, the Red Sea, and the Dead Sea; but the Runn of most recent tertiary strata, Dr. Buckland has shown that the Cutch in the delta of the Indus, and some of the lakes in the human remains must have been introduced subsequently, districts of Mount Ararat, explain to us how beds of salt are

That some rocks have been formed since the creation of man, is formed in the present day. Professor ABICH, in his notice of evident from the fact that they contain the remains of human “the Natron Lakes in the plain of the Araxes,” says that in one beings, implements of human art, and several vestiges and traces lake, at the north-west foot of the Greater Ararat, the water, in of the operations of man. In basins or hollows covered with peat the warmest season, retires three Pc on which a crust of salt a few feet broad and about half an inch and works of art are imbedded in company with the remains of thick is found deposited, of generally a pale rose-red colour. recent animals. On the west shore of the Red Sea a rock has Other lakes lying to the south-east of Little Ararat, are of the been formed composed of sands, gravel, corallines, pottery, and same description. One of them is remarkable for having a broad weeds, cemented by carbonate of lime, being in thickness from zone of white clayey soil covered with luxuriant reeds and an inch to three or four feet, and sometimes alternating with grasses. This soil forms the margin of the lake all round, and is thin and loose layers of shingle. This rock stands at five or six 80 soft that the feet sink in it. It is covered with an accumula- feet above the high-water level, overlying the raised coral beach, tion of irregular lump-like incrustations of a very compact salt, of and inclosing bones of camels and fish which to this day contain a white colour and inclining to red, and with a foliated structure. animal matter. On the shores of Sicily, Greece, Asia Minor and These saline crusts lie all around the white shore, chiefly floating Aden, similar marine calcareous rocks have been formed. in the water of the lake ; and some fragments that were broken Rhodes, at the height of six feet above high-water mark, a caloff floated about, like shoals of ice, on the deep-red surface of the careous conglomerate is observed that contains fragments of water, which had all the appearance of water just on the point of ancient pottery, recent shells, and. pebbles of limestone, gneiss, freezing. On examining the floor of the lake, as far as could be basalt, serpentine and porphyry. In several places on the caldone by tying several Cossack spears together, it was found careous cliffs that skirt the Mediterranean between Alexandria covered with a similar saline crust in unbroken continuity, and and Aboukir

, there is a bed, about a foot thick, consisting of appeared to increase in depth, from the shore, in such a manner ag bleached human bones, derived from the ancient Roman and Greek to leave no doubt that a layer of salt, several'inches thick, extends cemeteries, intermingled with those of the slain in battle in the over the whole bed of the lake.

neighbourhood. These bones are covered with a layer of sand Our space will not allow us to consider other rocks that are now

and gravel, varying in thickness from a few inches to three or four forming as sheets of lava, as volcanic cones, and as sand duncs.

feet. They appear to have been washed into their present posi

tion by the drainage water running from the higher grounds to II. ROCKS FORMED SINCE THE CREATION OF MAN.

What is remarkable in these bones is, that though they

are in an excellent state of preseryation, they are not fossilised. Every honest geologist acknowledges that he is not able to mark the point of union between historical and geological time, and that he cannot define where geological epochs terminate, and the historical era begins; that is, that he cannot tell, from the contents of rocks, at what time man appeared on the earth. If we might be allowed to argue in the old Aristotelian method, we might infer that, where we find in existence a large number of animals that seem to contribute to the use of man, we have also s'jme evidence of the existence of man: for, if the bones of the ox, the horse, the dog, the deer, &c., the bones of animals Waich are characteristic of the present creation, are found in the sediments of ancient lakes or the alluvium of ancient floods, there is nothing to prevent the indirect inference that the race of man had commenced when such beds were deposited.

When the attention of men was first directed to organic remains found in rocks, many fossil bones were mistaken for the bones of man. In 1577, Professor PLATER, of Basle, found near Lucerne, the bones of a man, which he made out to be a giant nineteen feet high. These turned out to be the bones of an elephant. SCHLEUCHZEE published an account of a fossil skeleton, under the title of “ Homo Diluvii Testis," or man a witness of the deluge. Cuvier afterwards proved that this was the skeleton of a gigantic Fig. 2. The present Cone of Vesuwius, with S09ırma to the loft, salamander or proteus. SPALLANZANI gave an account of a hill

and Naples in the foreground. in the Island of Cerigo, that consisted of fossil human bones; but BLUMENBACH showed satisfactorily that all of them belonged to Geologists can satisfactorily prove that a vast portion of the quadrupeds. Sir Alexander Cochrane brought and placed in the layas, the tufas, and the trap dykes of Etna, of Vesuvius, and of

the sea.

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