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ON PHYSICS, OR NATURAL PHILOSOPHY.-No I.

OBJECT OF THE SCIENCE.

senses.

The object of physics, or natural philosophy, is the study of all in the air, and a great number of other bodies, to which the phenomena which material substances present, except those general appellation gas or aëriform fluid is applied. In gases which relate to changes of internal composition; the latter the mobility of the molecules is still greater than in liquids ; but come under the domain of chemistry. For example, selecting the special characteristic of gases is their unceasing tendency the metal iron as a subject of contemplation, we may study its to expand into a greater volume; a characteristic expressed by specific gravity, its degree of hardness, its property of weld- the term expansibility, and which will hereafter be demonstrated ing, of being drawn out into wire, and rolled or beaten into experimentally. The general term fluid is applied both to plaies; all these phenomena depend upon the physical proper- liquids and to gases. The greater number of simple bodies, ties of the metal, and the study of such phenomena comes under and many compound ones, are capable of presenting themselves the domain of physics, or natural philosophy, sometimes called successively under the three forms of solid, liquid, and gaseous, mechanical philosophy. But iron is endowed with another | according to the variations of temperature to which they are set of qualities. It is capable of being dissolved in certain exposed. Of this successive change, water affords a well-known acids, and rendered invisible as iron, although its presence may example. Hereafter, when we farther advance into the regions be recognised by various tests. All this department of study of natural philosophy, it will be found that the three states of belongs to chemistry.

solid, liquid and gaseous, depend chiefly on variations of We have stated that matter (or material bodies) admits of molecular attraction and repulsion. being studied under two aspects : but what is matter? It is On Physical Phenomena.-Every change which the state of a necessary to arrive at some understanding as to this qucstion body may undergo without involving alteration of composition before proceeding farther. Perhaps the best definition of mat- is a physical phenomenon. The falling of a body, the sound ter is comprehended in the expression, whatever falls or is produced by such falling, the freezing of water, all are physical capable of falling under the immediate cognisance of the phenomena.

Laws and Physical Theories.--The term physical law is applied At this time, there are sixty-three known elementary or to designate the constant relation which exists between any siinple bodies ; that is to say, bodies out of which chemical particular phenomenon and its cause. For example, in demonanalysis has not succeeded in extracting more than one species strating the fact that a given volume of gas becomes one-half, of matter. Nevertheless the number sixty-three is by no one-third, one-fourth, &c., its original size, according as it is means to be regarded as the permanent representative of simple exposed to a degree of pressure, twice, three times, &c., we illusbodies. Possibly their number may hereafter be increased or trate the well-known physical law which is expressed by saydiminished, according as new simple bodies may be discovered, ing that the volumes of gases are in an inverse ratio to the or those with which chemists are at present acquainted may ( pressures under which they exist. A physical theory is the colbe proved to be made up of simple constituents.

lection of laws relating to the same class of phenomena. Thus Bodies, Atoms, Molecules.-Every definite or limited amount we speak of the theory of light, the theory of electricity. of matter is termed a body or mass, and the properties of such Nevertheless this expression also applies, though in a more bodies or masses show that the matter of which they are com- restricted sense, to the explication of certain particular pheno. posed is not continuous, but is made up of elements, as it were, mena. In this latter sense, we speak of the theory of daw, the infinitely small; so small that they are incapable of physical theory of mirage, &c. or mechanical division, and not in actual contact, but in near Physical Agents.-As causes of the phenomena which bodies proximity; the distances between them being maintained by present, philosophers admit the existence of physical agents or reciprocal repulsions, known under the name of molecular natural forces, by the operation of which all matter is governed. forces. These minute elements of bodies are terved atoms, These agents are universal attraction, caloric or heat, light, and groups of atoms are termed molecules,--of which latter, a magnetism and electricity. Mere physical agents only manifest body or mass is only an aggregated collection,

themselves to us by their effects, their ultimate nature being Mass.—The term mass of a body is applied to the amount of completely unknown. In the present state of science, the matter which it contains. The absolute mass of a body cannot question still remains undetermined, whether the physical be determined, but its relative mass, considered with regard | agents are to be regarded as properties inherent in matter, or to the mass of some other body taken as unity, can be readily whether they are in themselves subtle material bodies, impalarrived at.

pable, pervading all nature, and the effects of which are the Physical Conditions or States in which Bodies exist. These states result of movements impressed upon their mass. The latter are three, each being well characterised and readily distin- hypothesis is that most generally admitted ; but being admitguishable from the others. 1. The solid state. This condition ted, next follows the important question,—"Are these kinds of is manifested at ordinary temperatures by wood, stone, and matter distinct amongst themselves, or are we to refer them to metals. It is characterised by an entire adherence of mole- one and the same source?" This latter opinion appears to gain cules amongst themselves; so that they only admit of separa- ascendency in proportion as the boundaries of natural philosotion by the exercise of a certain degree of force, varying for phy become expanded. Under the assumption that the phydifferent solids, and for the same under different circumstances, sical agents are subtle forms of matter, devoid of all appreciIt is a direct consequence of this molecular adherence, that able weight when tested by balances of the highest sensibility, solid bodies retain their original forms. 2. The liquid state. they have been termed imponderable Auids ; hence arises the Of which we are furnished with examples in water, alcohol, distinction between ponderable matter, or matter properly and oils. The distinctive character of liquids is an adherence so called, and imponderable matter, or imponderable physical of so feeble a degree between their molecules, that the latter agents. slide upon and pass each other with extreme facility, in consequence of which it results that liquid bodies do not affect any

ON THE GENERAL PROPERTIES OF BODIES. external iorm of their own, but invariably assume that of the containing vessel, 3. The gascous state. Of this we have examples 1 or of matter is understood, the different methods by which they

Different Kinds of Properties.-By the term properties of bodies VOL. IV.

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come within the sphere of our cognisance. These properties diagram this correspondence occurs at the eighth division on are distinguished into general and special. The former are the vernier, counting from the point x. This coincidence those which belong to all bodies, of whatever kind and in what shows that the fraction to be measured is equal to eight-tenths. erer state they may be examined. The properties necessary to | In other words, the divisions on the vernier being snaiier than be considered at this time, are impenetrability, extension, divisi. than those on the fixed rule by one-tenth, it follows that if we bility, porosity, compressibility, elasticity, mobility and inertia. begin to count at the point of coincidence, and proceed in the Special properties are such as are observed in certain bodies, direction from right to left, each {uccessive degree on the ver. or under certain physical conditions. Of this kind are solidity, nier falls in arrear of the corresponding degree on the fixed fluidity, tenacity, ducnility, malleability, hardners, transparency, rule by one-tenth. Hence it follows, that in the case under colour, &e. For the present we shail only be concerned with consideration from the extremity s of the vernier, to the fourth the general properties of matter already mentioned ; but it is division on the fixed rule, the intervening space is eight-tenths, proper to remark that impenetrability and extension, are not and we arrive at the final conclusion that the length of the so much to be regarded in the light of general properties of object M N to be measured, is equal to four of the divisions of A B matter as the essential attributes of mater itself, and which plus eight-tenths. Consequently if the divisions on the great or serve to define it. Furthermore we may here remark, that fixed rule are hundredins of inches the length of x x will be the terms divisibility, porosity, compressibility, and elasticity obtained almost exactly correct to one-thousandth of an inch. only apply to bodies regarded as made up of aggregated mole- Were it desired to be still more accurate, to obtain the length cules; they are inapplicable to atoms.

correct to the two or three thousandth part of an inch, it would Impenetrability. This is the property by virtue of which no then be necessary to divide a B into hundredths of an inch, to cut two material elements can simultaneously occupy the same off the vernier rule until its length should be equal to nineteen point in space. This property, strictly speakina, only applies

or twenty-nine divisions of the great rule, as the case might be, io atoms. In a great number of cases bodies appear to be and tinally to divide the vernier into twenty or thirty equal parts. susceptible of penetration. For example, there exist certain But when such minule divisions as these have to be observed, alloys, of which the volume is less than the joint volume of the and the exact line of coincidence between the degrees of the ver. metals entering into their composition. Again, on mixing nier and the fixed rule accurately read off, the aid of a lens is water with oil of vitriol or with alcohol, the mix'ure contracts absolutely necessary. The vernier is not invariably a linear in volume. Such phenomena do not represent actual penetra.' measure, as we have already described it; very frequently yra. tion. The appearance is solely referable to the fact, that the duated circular arcs are supļlied with verniers, which are materials of which the acting bodies are composed are not in then usually engraved in such a manner that fractions of a actual contact. Certain intervals exist between them, and degree are read off in minutes and seconds. It may be proper these intervals are susceptible of being occupied by other here to remark that the vernier is also occasionally termed a malters, as will be demonstrated further on, when we come to monites, and still more frequently in mathematical books of a treat of purosity.

past era, the wonius pernier. I derives this name from Nunez, Ester.sion. This is the property which every material body! a Portuguese mathematician, who is considered by some to possesses of occupying a limited and definite portion of have been its inventor. This, however, is not the case. The space. A multiplicity of instruments has been cons:ructed, instrument of Nunez, although designed for accomplishing a raving for their object the measuring of space. Amongst similar purpose with the vernier, differed from it in some imthese the vernier and the micrometric screw are very portant respects, and was far less etficient. important; we will therefore proceed to their consideration. The Vernier is so called from the name of its inventor, a metric is applied to that variety of screw employed for measur;

The Micrometric Screw and Diriding Machines. The term microFrench mathematician, who died in 1637. This instrument ing with precision the extension of length and breadth. It enters into the construction of numerous kinds of apparatus follows, from the very nature of a screw, that when it is well used in the study of the physical sciences, such, for example, as : and accurately made, its pitch, or the interval existing between barometers, cathetometers, gosiometers, &e. It is composed of any tw. successive threads, must be everywhere throughout its two engraved rults, the larger of which ap (fig. 1), is fixed and length the same. From this it follows, that if a screw be ropadivided into equal parts. The smaller rule is moveable, and to ted in a fixed nut, the former will advance a certain equal disthis in strict language the term vernier is alɔne applicable. tar.ce for each revolution, the rate of advance being proper To graduate the vernier, the process is as follows. First of tionate to the degree of obliquity of the serew-thread. It tol: all it is cut to such a length as corresponds with nine divisions lows, moreover, that for every fraction of a turn, say itath, it of the large or fixed rule. It is then divided into ten equal only advances the both of the length of an interval between parts, from which arrangement it follows that every division any two threads. Consequently if this interval be equal to a of the rule a d is smaller than a division of the rule a B by hundreth of an inch, and it at the handle extremity of the screw one-tenth.

there is attached a wheel or circle gravluated into 100 divisions; Fig. 1.

and turning with the screw, then on turning the graduated

wheel through only one division, the screw itselt will be caused B to advance to the extent of one 400th of an inch.

Diriding machines, as they are termed, depend on the application of this principle. Fig. 2 represents a dividing machine, intended for the division of straight lines. It is composed of a lrg screw, the thread of which ought to be perfecuy regular, working through a tixed metallic plate, and its handle part attached to a fixed metallic circle 2. Adjacent to this graduated wheel is attached a fixed index B, by means of which every fraction of a turn made by the wheel, and consequent.y the screw itself

, may be easily discriminated. The nut

E, through which the screw piays, is attached to an iron rule The vernier being thus constructed as already described, let CD, which moves with the nut by a motion parallel to the axis us explain the manner of its application. Si it was desired of the screw. It is upon this rule which is fixed the object to measure the length of an object x x.

Vi pli'e it as repre.

m n intended to be divided. Lastly, the table is supplied with sented in the figure upon the great rule, th- 1 *nz axis of which two brass grooves perpendicular to DC, and upon which moves corr sponds with that of the bois to be mesured, and we the slide-rest a, armed with the steel graver o. find that its length equals four units in a certain frac- The machine being arranged according to the description tion. To value the amount of this irae wa is the object of just given, two different cases may present themselves. Either the vernier. This is accomplished by sliding the vernier the rule mw has to be divided into equal parts of a determinate along the length of the fixed rule, until the end of the vernier length-for example, four hundred.hs of an inch--or it may corresponds with the end us of the object in re measured. have to be graduateri into a given number of equal parts. Under This adjustment being made, we next seek for the point of the first conditions, the course of the screw, or its length from co.ncidence between the divisions of the two rules. In the thread to thread, being equal to one hundredth of an inch, the

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operator turns the circle a through one-fourth of an entire revo- substance in an apartment the air of which is frequently
lution, engraves a mark on the rule, then turns the wheel through renewed.
another fourth of a revolution, engraves another mark, and so Another example of the extreme divisibility of matter, even
proceeds until the operation is completed. Under the second when organised, is furnished by the globules of the blood.
conditions, let us suppose the division of the rule mn into Blood is made up of red globules, floating in a liquid termed
eighty equal parts to be the problem for solution. The serum. In man, these globules are spheroidal, and their dia-
operator now commences by causing the screw to turn in meter only amounts to about the .0003tb part of an inch.
the direction from right to left, as relates to our diagram, Nevertheless, the particle of blood capable of being taken up
until the extremity in exactly coincides with the point of the on the point of a needle contains nearly 1,000,000 of such
graver; then reversing the direction of rotation, and causing globules. But, what is more wonderful still, certain animals
the wheel to move from left to right, in relation to the diagram exist so amazingly small, that they can only be seen by the aid
until the other extremity n of the rule corresponds with the of a microscope of high power. They move about as large
point of the graver. The operator counts the number of turns, animals do; they are nourished ; they possess organs ; how

Fig. 2.

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and the value of the fraction of a turn, if such exist, gone | immeasurably small must those particles be of which sucu
through by the graduated wheel in causing the rule co to animals are composed !
advance from one extremity of the object mn to the other. The divisibility of any kind of matter having been pushed
Then, dividing the total number of revolutions by 80, the so far that its particles are altogether imperceptible, even by
quotient indicates the space along which the screw e must the aid of the most powerful microscope, experiments can
advance for each oth of mn. It only now remains to engrave no longer determine whether such matter be finitely or
a mark on mn at the cessation of each partial revolution of infinitely divisible. Nevertheless, the stability of chemical
the wheel.

properties belonging to each kind of matter, the invariability Divisibility. This is the property which all bodies possess ments, and other important considerations, point to

of relation subsisting between the weights of combining eleof being susceptible of division into distinct parts. Numerous belief in a finite limit to material divisibility. Circumstances examples might be cited illustrative of the extreme divisibility of this kind have led philosophers to assume that bodies are of matter, Thus one grain of musk is sufficient to evolve constituted of material elements not susceptible of division, during many years the peculiar odorous particles of that and to which, therefore, the term atoms is applied.

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LESSONS ON CHEMISTRY.-No. II.

latter is by far the more convenient plan of the two. I have TAKIng up the subject at the point where we left off in our

not assumed the student to possess a cork.borer, but I will certain operations on certain corks. He must then adapt these such as is employed for the ferrules of fishers' rods, of equal size last lesson, the reader will remember that he must perform describe the instrument, so that it may be made or procured at

a Florence flask, in such a manner that two instruments may be with the hole to be bored, and sharpened by filing to a rough formed as represented in the diagram annexed.

saw-edge at one end. If a transverse hole be bored through

the brass tube towards the other end, all the better: the conFig. 1,

Fig. 2

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The four-ounce bottel with its tobacco-pipe attachment, will
not be required just now, but we shall speedily want it, there-
fore let the arrangement be made at once. Now the treatment
of the cork involves two separate processes, boring and exter-
nal fitting, and the order in which these operations are per-
formed is not immaterial. The boring operation must come trivance permitting the insertion of an iron wire as represented
first. There are two methods of boring a cork; ether by by a, thus attaching to the instrument a sort of gimlet handle,
thrusting it pointed red-hot wire through it, and afterwards and conferring that kind of additional power which mechanics
accurately enlarging the orifice by means of a rat's-tail file, or term for the sake of brevity" purchase," -- with such an instru-
by the use of a special instruinent termed a cork-borer. The ment as this, cork-boring is a very simple affair. A cork-bore,

being taken of the proper diameter, its edge is sharpened by a sit remains to attach the length of India-rubber tubing to the few rubs of the file, and pressed against the cork under con- tobacco-pipe shank, and a few inches of glass tubing to that of tinuous rotatory motion, when it soon penetrates through the India-rubber, so that eventually an apparatus may result of the central core, escaping through the tube itself. As there is following shape, where a represenıs the point of attachment some little chance, however, that the side of the cork where the between the India-rubber tube, and tobacco-pipe shank; and hole emerges may assume a ragged aspect, it is better to commence the operation at une end of the cork, then without

Fig. 1. penetrating quite through withdraw the borer, and recommence at the other end, thus causing the operation to termi. nate in the middle. If the aperture be clean and smooth it may be considered finished ; if it be rugged and uneven, how. ever, it will require trimming with the rat’s-tail file. The aperture being made, we now come to the insertion of the tobacco-pipe shank, a matter of much simplicity ; one would think that no special instructions were necessary. It is not 80:- the operation requires to be set about in a systematic way; and although in this case, the operator mighi succeed after many attempts, and tobacco-pipes being cheap enough, these numerous atiempts might be made without the objection of great expense ; yet

considering the necessity for performing similar operations under modified circumstances to which the a'the point of attachment between the latter, and the associated objection of expense and many others would strongly apply, glass tube. Perhaps it is scarcely necessary to indicate that it is better to cultivate the right habit at once. Remember, round or oval glass flasks will not stand upright without some then, tobacco-pipes and glass tubes are not like metal rods. kind of support; they may require to be supported whilst exWe cannot fit them tightly, by violently twisting, turning, and posed to heat or after removal from heat. In the former case pushing, nevertheless we must fit them air-tight. Our object rings or triangles are usually employed, attached to a vertical is accomplished by easing them in, to use a popular but an stand, and capable of elevation or depression (fig. 6). Instruexpressive word. Their accuracy of adjustment is secured by ments of this kind can be procured ready made, but every paying attention to various little circumstances of detail. If, experimenter possessed of moderate ingenuity can prepare them then, the end of the tobacco-pipe shank be ragged, as it most or their substitutes for himself. A carpet-rod, around one likely will be, rub off those ragged inequalities by means of a extremity of which has been cast a block of lead, answers per. file. Had we been concerned with a thin glass tube instead fectly, and the rings may be made of stout iron wire, as of a tobacco-pipe, the better plan of treatment would have represented in fig. 6. consisted in melting the extreme end of the same by holding it for a few instants in the flame of a spirit-lamp or a jet of gas.

Fig. 3.

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Our present operations having reference to clay, not glass, we have not this resource; but on the other hand a tobacco.

An examination of the mechanical conditions to which the pipe shank is stronger than a glass tube, in consideration of wire ring is subjected will prove that it requires no screw or which I have chosen it, otherwise a piece of glass tube would other contrivance for fixing, when moderate weights have to have answered the purpose equally well.

be supported. Having finished the attachment of the tobacco-pipe shank, we now come to the attachment of the cork itself, which

is tions. The

subject of this lesson is zinc, but it is iron which

Matters are now ready for the commencement of our operaeffected by accurate filing, a slightly conical form being im- must first claim our attention. We require to effect a combiparted to the cork, in order that it may tightly fit with the nation of this metal with sulphur, in order that something may minimum of pressure. This precaution is especially requisite be made where with certain properties of the zinc may be when a thin necked flask has to be corked. In this case a tested. The combination of sulphur

with iron is called sula very slight amount of pressure will infallibly break the neck phurei of iron, occasionally the sulphide of iron, and let the uf the flask. The cork I will now assume to have been accurately adapted,

reader well remember that oy filing, to its orifice; but it is hard and rigid. Corks may be A SULPHide

A SULPHITE softened by immersion in boiling water, a treatment which will answer all present ends; but cases frequently present

A SULPhate. themselves when a cork, forming part of a chemical apparatus, must be absolutely dry, under which circumstances it must be the termination ide or uret express the same compound, but the softened by immersion in hot sand, or more extemporaneously, terminations ite and ate express two different compounds; dif. but less rapidly, by holding it for a few seconds in the flame ferent not only as materially between themselves, but as of a spirit-lamp. Having completed the arrangements to the extent described,

• The a to the right in the cut should be a'.

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between themselves collectively and a sulphuret or sulphide. a proper substitute must be found to take its place, and hence
What is the difference? No matier. That point will come under the terms water-bath, oil-bath, &c.
consideration by-and-by; we are not now treating of sulphur
compounds, but of the metal zinc. If the collateral facts just

Fig. 7.
mentioned choose to attach themselves to the learner's memory,
well and good ; if not, let them pass, they will be made to
attach themselves in the sequel. Sometimes, however, when
one gives a collateral fact on the understanding that it may stick

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A sand-bath consists of an iron dish (a saucepan answers very well) containing sand, and hung or rested over any convenient source of heat. A few pieces of lighted charcoal supply a very convenient source of heat; and by putting the lighted charcoal into a perforated earthenware flower-pot, strengthened by banding with copper or iron wire, we gain all the advantages of a furnace; a temporary grating may readily be made of strong wire, and the pots, pans, and other vessels to be heated may be supported on triangles of hoop iron, fig. 8.

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Fig. 8.

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in the brain or take flight just as best suits its own good plea

it sticks there all the firmer. I always give collateral facts an option of this kind. To effect the union of sulphur with iron, in other words, to make sulphuret of iron, it is merely necessary to bring a white-hot bar of iron in contact with a roll of sulphur; then the iron drops into melted globules which seem like iron itself, but which in reality are a compound of iron and sulphur, and weigh heavier than the iron by the weight of the sulphur where with they have combined. The greater number of metals can be made to combine with sulphur, by a similar treatment to that now described, and, indeed, perhaps the act or combination just effected may have presented itself to the reader's attention under the aspect of naiural magic. To melt a nail in a walnut-shell, is a proposition often constituting the subject of a wager. The learner now sees The preceding diagram represents a furnace of this kind, how that wager might be won. A nail being heated to white which may be worked on a table, the latter being protected ness, is dropped into a walnut-shell containing sulphur, when from heat by the intervention of a Welch tile or flat stone. Pro. the fusion of the nail immediately takes place.

bably the furnace will crack, owing to the intense heat Let the sulphuret of iron thus resulting be transferred to a within. It is, however, none the worse for this accidentbottle labelled Sulphuret of Iron, and put away,—we shall the binding wires prevent all separation between the various require it presently. We will now return to the zinc solution, pieces of which the furnace is composed; and, in short, the which has been so long neglected that the student may fear furnace is no less useful than before. the original subject of the lesson has been forgotten. Not so. Supposing the solution of zinc in oil of vitriol and water to Every point ex patiated on, everything done, has had reference be placed in a saucer or porcelain dish, specially made for the to the metal zinc.

purpose, under the name of evaporating dish ; supposing the I have already said that the metallic zinc employed remains solution and its dish to be embedded in the sand-bath, and in the solution; the next point, then, is to ascertain the con, the latter placed on its hoop-iron tripod over a fire, heat will ditions it has assumed, and this information may be obtained rapidly penetrate the sand, and evaporation will ensue. If by driving off the liquid in which it is dissolved. This is the solution were to be evaporated very slowly, the saucer or accomplished by the application of heat, which, causing the pan would eventually contain white crystals. If, however, liquid to become steam or vapour, the latter is driven off, and the evaporation be more rapidly pushed, then crystals do not all bodics contained in the liquid, not capable of assuming appear, but a white confused mass. I suppose the latter to this vaporous condition, necessarily remain.

As soon as evaporation is complete, and the The application of heat in many processes of evaporation residue has become thoroughly dry, remove the saucer from and distillation requires many precautions. For the most part the sand-bath, allow it to cool, and when cold dissolve the naked tires are ineligible; frequently a sand-bath is the best evaporated material in distilled water. The liquid now returns means of applying heat, and it is the source of heat we shall to the state in which it originally was before evaporation, with einploy now, fig. 7; but occasionally the heat capable of this difference, any excess of oil of vitriol over and above the being imparted by sand would be injuriously high, hencel quantity necessary to dissolve the zinc, has been driven away

be the case.

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