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stupendous conflagration of hydrogen gas—in plain English, that Vie star mas on fire! A spectacle such as this suggests the reflection that an analogous catastrophe, albeit very improbable, is by no means impossible with our own Sun. We have previously seen how abundant hydrogen is on his surface, and how the marvellous red prominences, always visible during a solar eclipso, arc composed of it, so that the material for combustion is present in enormous quantities. Of the nature of the agency requisite to set up sufficiently energetic action we know literally nothing, and it would be merely idletospeculatcuponit; but of the result of such a convulsion there can he uo doubt whatever. The intensity of the Sun's rays would be increased some eight hundredfold, and our own globe, and everything on it, would be instantly dissipated in the form of vapour. It may be worth while to add, that Secchi has observed bright bands in the spectra of more than one minute star, though without determining their position; so that wo are unable to say whether they indicate a similar condition of things to that which obtained in tho star in Corona or not, but that the spectrum of y Cassopeirc (Vol. X., Map, p. 25) certainly resembles that of T Corona;, the star of which we have been speaking, to a very considerable extent. (To be concluded.)

ELECTRICITY—ITS THEORY, SOURCES,
AND APPLICATION.

BY J. T. Sf-hague.*
{Continued from paje 196.)

ШТЬе fluid surrounding the zinc may • be the usual acid, or where great action is not needed, common salt, or sal ammoniac, and other substances are used, or for telegraphic purposes, pure water; in these cases the zinc need not be amalgamated, which has this advantage, that any copper reduced on it docs not combine, but causes lesa local action, and is more easily removed. For purposes of comparison, I made a cell of this kind fitted with plates 2in. by 1, and Jin. apart, as before. Charged with acid this gave 32", with sal ammoniac 30", with common sa't 27е, and¿ other ¡salts, such as

sulphate of soda and nitrate of soda, were still still less effective. It will be noticed that these figures are much lower than gome of the previous forms, but it would bo erroneous to suppose that this signifies lees force; the Daniell's cell has a higher force than tho Smee at its best, but it has a much higher internal resistance of one kind to overcome—viz., the porous division ; this, with the Smee form, with the plates on opposite Bides of the division, reduced it from 50" to 35°. But when different batteries are doing actual work, the result is that the power of the Smee is reduced in much greater degree than that of the Danicll, while the latter continues to act steadily. This is exemplified by the following comparison of a good working Daniell's coll, which, at its utmost work, only gave ôC, with my powerful cell giving 81°, with different resistances interposed :—

Units 12 3 4
Daniel! 50 27 20 13 II
Mine 81 33 21 14 11

It must be understood that the actual variation is much greater thou these figures, as it is in the ratio of their tangents. I have prepared, at great cost of time and labour, a complete table, which will be appended to the paper on Galvanometers, and will give the readers of the Ekglish Mechanic a more complete conception of this and of the teachings of galvanometers than has been furnished in any work hitherto published; at present I need only say that 50 has a value of 68, while 27 is 29, a difference of 39, or 55 per cent, while 81 and 33 represent 3C2, and 37 a difference of 325, or 89 per cent., caused by the first unit of resistance. ^¡ï

125. I believe the flat form to be the most convenient, but when cylinders are,used, it is doubtful whioh way is best to arrange them—as described and usually made, or with the copper inside. The latter has the advantage of giving a larger area of diffusion to the leakage of copper salt, while it is not necessary to use a cylinder of zinc, for 1 or 2 rods or slips will furnish all the necessary foroe,

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as the coppor surface is so much diminished ; thus one cell will not give off so much current on short circuit as in the ueual form, but this is not of much consequence. Fig. í¡9 shows a cell arranged in this manner with a reservoir of crystals in a flask, as there is no capacity for it in the cell. The flask is closed with a perforated cork, fitted with a glass tube, which dips below the surface of liquid in the cell, and keeps up the supply on the principle of the bird fountain. Such a cell, provided with two or three wire gauze cylinders, between tho zinc and the porous jar, would probably furnish a constant current for a prolonged period ; this is called the Meidinger cell. There are many other modifications of the Daniell, vauHted by their makers, but there are only two calling for any remarks, beeause they are frequently mentioned.

120. Tub Min Otto has been much lauded; it consists of a jar, at the bottom of which is а copper plate, fitted with a wire, this is covered with an inch of crushed sulphate of copper, and this again with a layor of silver sand, which is to act as tho porous division. My own experience with it is that it has all the evils of the ordinary form, and fow of its advantages ; the copper finds its way to the zinc very soon, while the resistance is so great that there is little power to spare; a full-sized one, with a plate 4Jin. diameter, only gave 15° and 13" after two days, during which it had done no work, but by which time there was a great deal of copper on the zinc. I have tried several modifications, hut all with the same result.

127. Boulay's cell, is another attempt to overcome the ovils of the Daniell. It is very peculiarly constructed, tho porous jar being double, and containing both metals as cylinders, separated by paper and by crystals of common salt ground up with equal bulk of flour of sulphur surrounding tho zinc, and equal bulks of sulphate of copper and nitrate of potash around the copper; the cell, thus tightly packed, is placed in a jar containing crystals of copper sulphate and water. The patentee claims great advantages for this cell, stating that tho sulphur has a peculiar property by which, though itself unacted on, it prevents the passage of the copper salt to the zinc, and that the addition of the nitrate of potash greatly adds to the electro-motive force. It has, no doubt, good properties, and once set up gives no further trouble, and is, I understand, about to be largely employed by the Government in the telegraphic department.

I found its action much stronger than I expected at first, as one cell gave 37°, rising in two hours to 55. It was then set aside for a week, doing no work, after which it gave 25u, falliug to 20, and I find that it remains with a power of about 20 to 16, so that it is very useful for experimental purposes, and would, no doubt, remain a long while in action with bells and alarms for domestic use, and require no attention. On the other hand when exhausted it would be troublesome to re-charge.

128. The thoory of the action of the sulphate of copper cell is easily explained as an extension of that shown in Fig. 36, p. 75. If we imagine the porous partition in the middle and the two right hand molecules to be sulphate of copper,

cell, with an addition for excess of local actiorj varying in each case, and the extra cost belonging to each special form; in the Daniell, this is the sulphate of copper, worth about 5d. per pound, but as it yields one-fourth its weight of copper as a residue, the price may fairly be set at 3d. Using for convenience and intelligibility the pound in all cases, multiplied by the equivalent weight, and dividing by 7000, the number of grains in а pound, we get the coat on the scale of grain equivalents, which is that I shall adopt, the unit of quantity or total current being one equivalent of any metal deposited or water decomposed :—

Sulphuric acid equivalent 49

local action, say 5 per cent. 2J

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Tho last line shows us that what occurs is that an atom of zinc is taken up and one of copper displaced, that the source of the force is simply tho difference of affinity of sulphuric radical for zinc and copper ; the foroe yielded is equivalent to the heat zinc would give while precipitating copper from its sulphate, and is really the difference between the internal force necessary to the oxistence of sulphate of copper, and that bound or latent in sulphate of zinc. It is probable, however, that it is only at the last molecule that copper sulphate forms part of the circuit if there is free aoid present, but that does not affect this principle, which seta the action before us far more comprehensibly than the idea that water, or even acid is decomposed, and completes the circuit, while tho nascent hydrogen merely reduces the copper chemically.

129. I havd dwelt thus fully on this form, because of its importance, both practical and theoretical, and it only remains now to show the cost of its working ; this will be the same as the simple

ANCIENT COINS.—III.
By Hexby W. Hesfbey.
(Continued from page 197.)

WE will now give a few particulars concerning the Imperial Roman series. They commence with Augustus, Emperor from 27 B.c. to A.D. 14.

The copper and brass imperial coins are extremely numerous, and of great interest. The usual divisions of them—which are purely arbitrary—are into large, middle, and email, or 1st, 2nd, and 3rd brass coins. The large brass is perhaps the sestertius; the second Ьга9в, when of brass, is the dupondius, and when of copper, the **, "In the reign of Philip wo find a ooia rather larger than the usual third brass, called the Philippus œreus, and in the time of Gallienus, although tho sestertii and dupondii cease altogether as a rogular series, there are small coins of brass, which we may suppose to represent the as. In the reign of Diocletian a new coin of copper appeared, termed the follis. This and a smaller coin (the assarius), both of which gradually decrease in size, continue till the reign of Honorius." (Madden.)

Copper or brass medallions were made of « larger size than the first brass coins. They were not struck for circulation as money, but probably served the same purpose aa our modern medals.

A complete series of Roman large brass is very costly. The superior size of these pieces, and the beauty and interest of their reverses, combine to make them of great value. With Gallienus, A.B. 268, they terminate. Among the scarce and interesting types are the following :—One of Livia with her bust, and Ivlia Avovsta Oesetrix OKBis. This latter title was conferred on her by the Senate. Coius of Drusns, commemorating his conquest of the Germans, hence cillod QermaKicvs. One of Claudius, with reverse a triumphal arch, and De Britaxxis, relating to his triumphs in Britain. Another of Vespasian, bearing в female figure of Judœ», seated weeping under a palm treo; inscription, Ivdaïa пагтл referring to the conquest of Judan and destruction of Jerusalem, A.d. 70. Others of Titus, similar, and commemorating the same events. One of Trajan smiting a Dacian foe. Others with fine portrait« of Antoninus Pius,Marcus Aurelius, the two Faustinas. The famous medallion of Commodus with Britania. The vici Bbit. of Gets, &.C.

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The engraving No. 5 represents the reverse of a large brass coin of Antoninus Pius, bearing a seated figure of Britannia. The reader interested in these coins should procure Akerman's " Coins of the Romans relating to Britain."

The second or middle brass coins are also very numerous, and often have similar types to the large brass. The third or small brass, however, are those of the most frequent occurrence. Among the commonest are those of Probus—of which several thousand varieties have Ьэеп found —Constantine, and his sons. With the small copper are classed plated coins, and pieces of mixed copper or tin, washed with silver, called billon.

The silver Imperial coins consist of denarii and quinarii, generally smaller than the Consular coins of the same denominations. The reduction from 8-1 te 96 to the pound is supposed to have been made by Nero. This latter standard would make the full weight about 52 grains troy. "In the reign of Caracalla (a.d. 211—217) a silver coin of a larger size appeared, called ' Argenteus Antoninianus,' having always the radiate head of an emperor, as Apollo, or that of an empress, as Diana. There were sixty struck to the pound: the coin was always of base silver; and, in the reign of Volusian (a.d. 251—251), the standard became extremely base, and the metal was either copper or tin, both covered with a wash of silver, In the reign of Diocletian (A.D. 284—305) good silver reappears, and is found to the end of the empire. The coins were still of two sizes, probably the 'argenteus' and the 'denarius.' The principal silver coin of Constantine the Great (a.d. 306—337) was the cententioiialis, which is most likely the silver coin, which weighs B little less than fifty grains: when it was first issued is not certain." (JTadde*.)

The series of Imperial silver is by far the cheapest and most easily obtained, bosides being extremely interesting from its great variety, curiosity, and beauty. The types are so numerous that we find it impossible to name the most interesting ones. In the words of Pinkerton, "They contain figures of deities, at whole length, with their attributes and symbols; public buildings and diversions; allegorical representations; ceremonies, civil and religious; historical and private events ; figures of ancient statues ; plants, animals, and other subjects of natural history; ancient magistracies, with their insignia ; in short, almost every object of nature or art."

The one «hich we have selected for illustration is a silver denarius of Tiberius Cecear, Emperor from A.d. 14 to A.D. M. It is called the tribute money, being one of the identical coins spoken of in Matthew, chap. xxii. "But Jesus perceived their wickedness, and said, Why tempt ye me, ye hypocrites? Show me the tribute money. And they brought unto him a penny [literally, a denarius]. And he saith unto them, Whose is this image and superscription? They say unto him, Ca?«ar's." The coin has, obverse, the bust of Tiberius Caesar. Inscription: Ti. Cesar, Divt. Avg. I. AVorSTVs; showing the name Caesar at full

length, lîrverse, the female figure seated. Poxtip. Maxim. See the engraving, No. 4.

The gold Imperial coinage consists chiefly of the aureus, but there are apparently doubleaurei and half-aurei, and other divisions, all of fluctuating weights. Augustus struck 40 aurei to the pound, Nero 45, Caracalla 50, and Gallienus still more. Diocletian made CO out of a pound, and Constantine the Great issued a new coin, the solidus, instead of the aureiu. The solidus was coined at the rate of 72 to the pound until the termination of the Empire. In size and type the aurei are very similar to the denarii, many types being the same in silver and gold.

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THE SCENERY AND GEOLOGICAL STRUCTURE OF A COUNTRY. *

THE subject I have chosen is to some extent new to many, and I think it promises to bring with it a new s mice of intellectual pleasure to us, in that it may be made a source of agreeable mental exercise. I can say, from my own experience, that it has enabled me to pass many B long and tedious railway journey much more pleasantly than I could have parsed it had I been ignorant of the simple truths I am about to place bofore you. We know that tastes and pursuits of this sort are powerful engines of cnlightment and truth ; and that they tend very much to keep us ont of that mischief which, the prophet tells us, is always ready for idle hands into. The necessary knowledge for this recreation lies within the reach of every one. It is not like going into the full study of Geology—that takes a lifetime. This pleasant application of science requires little more than i good are of the eyes, and plain, homely, common sense.

The delight in natural scenery and the power

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of appreciating its beauty is one of gradual growth in the human mind ; and I think it is a product of comparatively recent date. If we look at tho great poets of antiquity, we find what appears to us a surprising deficiency on this head. I do not mean to say that these writers have not given us many accurate and exquisitely expressed description of what they saw around them; but I do think that we fail to find that feeling of joy, and that delight in pure, natural, beauty for its own sake which every modern writer of cultivated mind shows, whether he intends it or not, I must preface my lecture with some slight attempt to prove this point. I suppose, for instance, that Mount Etna is one of the loveliest objects in the world. Sir Charles Lyell, describing it from a purely scientific point of view, could not resist the impulse of paying a passing tribute to the charms of its scenery. Pindar, by a few well-chosen epithets, brings before us every feature of the scene the snowy cap, the belt of dark-leaved vegetation below, and the startling phenomena of volcanic action. All this ho evidently saw, and he described it in a manner which cannot be surpassed; but I do not think that he experienced the same delight that a modern writer or traveller would have felt, lind he been gazing on so beautiful a country. The con tract appears to be very curious. We have a scientific man going out of his way, as it were, to speak of it with enthusiasm, and we have a poet entirely omitting to give such expression to his description. The solution of this is that the one had, and the other had not, this sense of the beautiful. Then, again, there is another famous passage in which Virgil describes his own fatherland, Italy. There is a long and detailed list of all her material advantages expressed in elegant and graceful language, but I must confess that it rather reminds me of an auctioneer's catalogue; and I think it would have excited the admiration of the famous Goorpe Robins, if ho could have read it. Italy, we all know, is looked upon as the home of loveliness, and it seems very strange to us that a poet writing in praise of his own country should have omitted this. If wo come down to more modern times, I always fancy, when reading Pope, that he seems to love the forest for its shade, and not for its intrinsic beauty ; and valued brooks and rivers, not as points in the landscape, but as possible bathing or drinking places for his nymphs. Then, again, there is a passage in Macaulay respecting a man who had been travelling in Scotland, and the only impression which seems to have been produced upon this man's mind was, that its mountains were "unsightly excrescences." Many of the pictures of the great masters of painting exemplify this want of appreciation of the beautiful in nature. They certainly did study one natural object with very great attention—viz., the human form, to the effect lam afraid, of sometimes making its anatomical ilutails very conspicuous in the picture. But they were very indifferent to most natural things; in fact, if we confine ourselves to our own literature, I think it is not until the time of the Lake School, Scott, and Byron, thatthislovc for natural scenery seems to have been fully developed. Since then it has been universally cultivated and enjoyed. Now I think that science is in a fair way to add to this lately-aoquired source of pleasure, for it will, before very long, fully explain tous the way in which different features of landscape were produced ; and this will necessarily add very much to our enjoyment when gazing at such a landscape. The scenery of a country will depend in a great measure on the shape of the ground: whether it is hilly, mountainous, flat, or traversed by deep or broad valleys. When we wish to see the connection between scenery and geology, we must first see her; it had its appearance given to it. Hills and mountains, valleys and deep gorges seem, very striking to us, but if we look at them in comparison with the size of the whole earth, they appear as little bulges on its surface. Now, the earth is enveloped in two thin external shell, which is made up of a number of substances, such as limestones, sandstones, clays, gravels, &c, all of which are known geologically under the name of rocks ; and a very large proportion of these rocks were originally formed of sand, mud, and soft sediment, whioh was carried down by rivers to the sea, and allowed to fall to the bottom. Thus the sea-bottom was gradually raised up until at last it was elevated into dry land. Now it was while this elevating process was going on that the land first began to assume its present shape. We need not for our present purpose concern ourselves with the way iu which the sediment was brought, or where it came from ; I ask you to

believe me when I tell you that the sediment was carried intotheeea, and that after it had remained there and increased in bulk by continual additions, it gradually got above the level of the water, and became dry land.

As soon as any portion of the sea-bottom is raised above the level of the water, it is attacked by a number of forces which tend to wear it away, and carve out inequalities in it, and it is to these forces almost exclusively that the present shape of the land may be said to be owing. These denuding forces are divided into two classes. 1. The sea ; which is called the marine denuding force. 2. The wind, frost, ice, and rain, which are called sob-aërial denuding forces. We will first take the action of the sea ; and it is of the utmost importance to note that at great depths the sea exerts little—I think I may say no denuding power at all. It is only able to exert a weariDg-away netion in shallow water, and' along coast lines. At these spots, the waves are constantly wearing and tearing away whatever rises above the water; and in this way they are aided very much by subaerial agents. They sweep clean away everything that rises against them, and plane the land down, as belt after belt comes within the range of their denuding action ; so that, at last, the result is B tolerably level surface. When the land is removed beyond the reach of marine action, its surface will most probably be very nearly level, with a small slope seawards. Then rain will begin to fall upon it, and form brooks and rivers, which will cut their way into the ground, and make a branching system of trenches across the plateau. The channels thus cut will be of a steep-sided, tren h-like form ;but the action of rain, frost, and springs will tend gradually to round off these sharp edges, so that by degrees the trench will become widened more and more, and at last spread out into a broad valley. This is now pretty generally admitted to be the most probable manner in which the contours of the oarth's surface пате been formed. The sea first makes a plain; the different brooks and rivers carve out systems of boundaries ; similarly as a man cuts a slab of marble ont of the quarry and takes it to the sculptor, who carres out a group in relief on it. Valleys are not rents and cracks torn open in t ea 'th's surface, but channels eaten out below tho level of the ground by rivers.

Let us see if we cannot somewhere find traces of old marine denudation. If we post ourselves on a central commanding point of a group of moontains, we are at once struck with the fact that a large number of the hill tops appear to rise much to the same level ; and if we take a raised map of this country, and lay over it a sheet of plate glass, we shall find that our first impression is correct; we should find that the sheet of glass would lie along in such a manner as to touch the tops of very nearly all the principal hills. That sheet of glass represents what was at one time the level of the whole country; wherever the surface sinks beneath it portions have been swept away by subnörial denudation, and the mountain tops and elevated plateaux are the only parts of the original surface that remain. I once saw a very striking instance of such traces remaining. I started one morning from the frontiers of Portugal to ride across Andalusia towards Seville, and I saw what seemed to be, as far as the eye could reach, an endless flat. I thought I should have an easy journey, and a speedy arrival at the end of it ; but I had not travelled much more than half an hour before I found out I was mistaken. I found the country traversed in every direction by valleys, some of which were so steep-sided as to deserve the name of gorges. You mightalmost riile up to the edge of one before you had any idea of its existence. When I turned back and viewed the landscape I could scarcely believe but that I had passed the entirely unbroken, flat country which it seemed.

(To be concluded)

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KEYES' IMPROVED WAGGON WHEEL.

FIG. 1 is a perspective view of the central рогtion of one of these improved wheels, with a portion of one of the iron flanges of the hub broken away to show the way in which the spokes are inserted; and Fig. 2 is a eection of the same, revealing the entire constructioo of the hub, and the manner of inserting and fastening the spokes. A, I'igs. 1 and 2, i« an external hub of malleable cast iron, lined with an internal hub of wood, B, Fig. 2. The inner and larger portion of the external hub A, is recessed, as shown, and a shoulder to correspond is made upon the internal

gravings; each alternate spoke С being wedged, as shown in Fig. 2, and the others D, Figs. 1 and 2, being shorter, and resting upon ledges of iron which rise between the extremities of the longer spokes, and serve to greatly strengthen the central part of the hub.

The axle box may be driven and rotained in the hob with much greater force than in a plain wooden hub, with iron bands, and the parts of the whole structure mutually sustain each other under strain. The hubs may be used for new wheels, when the other parts of the wheel are worn out.— Scientific American.

ENGLISH МИСТГ.1УГС MUTUAL IMPROVEMENT
SOCIETY.—MANCHESTER BRANCH.

A "second meeting was held on May 16, and the officers to the society elected, with a coraniittce to draw the rules, which will be submitted to the society members next meeting. The business on this occasion will be the inaugural address from the President, and a paper on "A New Solution to the Parallelogram of Forces," by the Secretary. The meeting to Be held at the Manchester Mechanics' Institution, David-street, on June 1, at 4 p.m., precisely

MECHANICAL MOVEMENTS.. (Continued from page 200.) 1 OR THREE-LEGGKD pendulum escapeJv/U« ment. The pallets are formed in an opening in a plate attached to the pendulum, and the three teeth of the escape-wheel operate on the upper and lower pallets alternately. One tooth is shown in operation on the upper pallet.

107. A modification of the above with long stopping teeth D and E. A and B are the pallets.

108. A detached pendulum escapement, leaving the pendulum P free or detached from the escapewheel, except at the time of receiving the impulse and unlocking the wheel. There is but one pallet, 1, which receives impulse only during the vibrations of the pendulum to the left. The lever Q locks the escape-wheel until just before the time for giving the impulse, when it is unlocked by the click C, att ached to the pendulum. As the pendulum returns to the right, the click, which oscillates on a pivot, will be pushed aside by the lever.

109. Mudge's gravity escapement. The pallete А B instead of being on one arbor are on two, as shown at C. The pendulum plays between the fork-pins P Q, and so raises one of the weighted pallets oot of the wheel at each vibration. When the pendulum returns the pallet falls with it, and the weight of the pallet gives the impulse.

110. Three-legged gravity escapement. Te lifting of the pallets A and B is done by the three pins near the center of the escape-wheel, the pallets vibrating from two centres near the point of suspension of the pendulum. The escape-wheel is locked by means of stops D and E on the pallets.

111. Double three-legged gravity escapement. Two locking-wheels ABC and abc are here used with one set of lifting-pins between them. The two wheels are set wide enough apart to allow the pallets to lie between them. The teeth of the first-mentioned locking-wheel are stopped by a stop-tooth D on one pallet, and those of the other one by a stop-tooth Ë on the other pallet.

112. Bloxam's gravity escapement. The pallets are lifted alternately by the email wheel, and the stopping is done by the action of the stops A and B on the larger wheel. E and F are tho fork-pins which embrace the pendulum.

113. Chronometer escapement, the form now commonly constructed. As the balance rotates in the direction of the arrow, the tooth V on the verge, presses the passing-spring against the lever, pressing aside the lever and removing the detent from the tooth of the escape-wheel. As balance returns, tooth V presses aside and passes spring without moving lever, which then rests against the stop E. P is the only pallet upon which impulse is given.

111. Lever chronometer escapement. In this the pallets А В and lever look like those of the lever escapement 296: but these pallets only lock the escape-wheel, having no impulse. Impulse is given by teeth of escape-wheel directly to a pallet C attached to balance.

116. Conical pendulum, hung by a thin piece of round wire. Lower end connected with and driven in a circle by an arm attached to a vertical rotating spindle. The pendulum-rod describes a cone in its revolution.

11G. Mercurial compensation pendulum. A glass jar of mercury is used for the bob orweight. As the pendulum-rod is expanded lengthwise by increased temperature, the expansion of mercury in jar carries it to a greater height therein, and so raises its centre of gravity relatively to the rod sufficiently to compensate for downward expansion of the rod. As rod is contracted by a reduction of temperature, contraction of mercury lowers it relatively to rod. In this way the centre of oscillation is always kept in the same place, and the effective length of pendulum always tho same.

117. Compound bar compensation pendulum. C is a compound bar of brass and iron or steel, brazed together with brass downwards. As brass expande more than iron, the bar will bend upward as it gets warmer, and carry the weights w w up with it, raising the centre of the aggregate weight M W to raise the centre of oscillation as much as elongation of the pendulum-rod would let it down.

118. Watch regulator. The balance-spring is attached at its outer end to a fixed stud R, and at its inner end to staff of balance. A neutral point is formed in the spring at P by inserting it between two curb-pins in the lever, which is fitted

~~* Extracted from a compilation by Mr. H. 1. Brown, Editor of the .laid can Artisan.

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lo (urn on a fixed ring concentric with staff of balance, and the spring only vibrates between this neutral point and staff of balance. By moving lever to the right, the carb-pins are made to reduce the length of acting part of spring, and the vibrations of balanceare made faster; and by moving it to the left an opposite effect ie produced.

(To be continued.)

ON THE RELATIONS BETWEEN BODY

AND MIND.»

Lecture I.

(Continued from page 199.)

TAKE, for example, the so-called faculty of memory, of which metaphysicians have made somucb, as affording nstheknowledgeof personal identity. From the way in which they usually treat of it, one would suppose that memory was peculiar to mind, and far beyond the reach of physical explanation. But a little reflection will prove that it is nothing of the kind. The acquired functions of the spinal cord, and of the seusory ganglia, obviously imply the eiistencc of memory, which ie indispensable to their formation and exercise. How else could these centres be educated? The impressions made upon them, and the answering movements, both leave their traces behind them, which are capable of being revived on the occusions of similar impressions. A ganglionic centre, whether of mind, sensation, or movement, which was w ithout memory, would be an idiotic centre, incapable of being taught its functions. In every uerve-cell there is memory, and not only so, but there is memory in every organic element of the body. The virus of small-pox or of syphilis makes its mark ou the constitution for the rest of life. We may forget it but it will not forget u», though, like the memory of au old man, it may fade and become faiut with advancing age. The manner in which tl.с scar of a cut in a child's finger is perpetuated, and grows as the body grows, evinces, as Mr. Paget has pointed out, that the organic element of the part remembers the change which it has suffered. Memory is the organic registration of the effects of impressions, the organisation of experience, and to recollect is to revive this experience—to call the org mised residue into functional activity. The fact that memory is accompanied by consciousness in the supreme centres does not alter the fundamental nature of the organic processes that are the condition of it. The more sure aod perfect, indeed, memory becomes, the more aneanscious it bponme«: and when an idea or mental

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MECHANICAL MOVBS1ENTK

state has been completely organised, it is revived without consciousness, and takes its part automatically in our mental operations, just us a habitual movement does in our bodily activity. We perceive in operation hero the same law of organisation of conscious acquisitions as unconscious power, which we observed in the functions of the lower nerve centres. A child, while learning to speak or read, has to remember tho meaning of each word, must tediously exercise its memory ; but which of us finds it necessary to remember the meanings of the common words which we are daily using, as we must do those of a foreign language with which we are not very familiar? We do remember them, of course, but it is by an unconscious memory. In like manner, a pnpil, learning to play the pianoforte, is obliged to call to mind each note; but the skilful player goes through no such process of conscious remembrance ; his ideas, like his movemenis, are automatic, ami both so rapid as to surpass the rapidity of succession of conscious ideas and movements. To my mind, there are incontrovertible reasons to conclude that the organic conditions of memory aro the same in the supreme centres of thought as they are in the loner centres of sensation and of reflex action. Accordingly, in a brain that is not disorganised the org.nie registrations are never actually forgotten, but endure while life lasts; no wave of oblivion can efface their characters. Consciousness, it is true, may be impotent to recall them; but a fever, a blow on the head, a poison in the blood, a dream, the agony of drowning, the hour of death, rending the veil between our present consciousness and these inscriptions, will sometimes call vividly back, in a momentary fl ish, much that seemed to have vanished from the mind for ever. In the deepest and must secrot recesses of mind, there is nothing hiddcu from the individual self, or from others, which may not be thus sometimes accidentally revealed; so that it might well be that, as De Quincy, surmised, the opening of the book at the day of judgment shall bo the unfolding of the everlasting scroll of memory.

As it is with memory, so it is with voliti n, which is a physiological function of the supreme centre?, and which, like memory, becomes more unconscious and automatic the more completely it is organised by repealed practice. It is not man's function in life to think and feel only; his inner life he must express or utter ¡u action of some kind—in word or deed. Receiving the impressions from natu: e, of which lie is a part, he reacts upon nature intelligently, modifying it in a variety of ways; ihns nature passes through human nature to a Ligner evolution. As the spinal cord reacts to : s impressions in excitomoior action, and as the sensory centres react to

their impressions in sensori-motor action, so, aftoc the complex iuterworking and combination of ideas in the hemispherical ganglia, there is, in like manner, a reaction or desire of determination of energy outtfards, in accordance with the fundamental property of organic structure to seek what is beneficial and shun what is hurtful to it. It is this property of tissue that gives the impulse which, when guided by intelligence, we call volition, and it is the abstraction from the particular volition which metaphysicians personify as the will, and regard as their determining agent. Physiologically,wecannot choose butrejectiAe will; volition we know, and will we know, but the юШ, apart from particular acts of volition or will, we cannot know. To interpose such a metaphysical entity between reflection aud action thereupon, would bring us logically to tho necessity of interposing a similar entity between the stimulus to the spinal cord and its reaction. Thus, instead of unravelling the complex by help of the more simple, we should obscure the simple by speculations concerning the complex. As physiologists we have to deal with volition as a function of tho supreme centres, following reflection, varying in quantity and quality as its cause varies, strengthened by education and exercise, enfeebled by disuse, decayiug with decay of structure, and always needing for its outward expression the educated agency of the subordinate motor centres. We have to deal with will, not as a single midecomposable faculty unaffected by bodily conditions, bnt as a result of organic changes in the supreme centres, affected as certainly and seriously by disorder of them as our motor faculties are by dis. order of their centres. Loss of power of will is ono of the earliest and most characteristic symptoms of mental derangement ; and, whatever mav have been thought^ in times past, we know well now that the loss is not the work of some unclean spirit that has laid its hands upon the will, but the direct effect of physical disease.

Bnt I must pass on now to other matters, without stopping to unfold at length the resemblances botweeu the properties of the supreme centres a nd those of the lower nerve centres. We see that the supicme centres are educated, as the other centres are, and the better they are educated the better do they perform their functions of thinking and willing. The development of mind is a gradual process of organisation in them. Ideas, as they aro successively acquired through the gateways of the senses, are blended and coinbiucd and grouped i и a complexity that delies analysis, the organic combinations being the physiological conditions of our highest menial operations— reflection, reasoning, and judgment. Two leading ideas are onght to grasp and hold fast: fir.^t, that ¡he со m plcx and more recxdi'.e phrai mena of mind »-e forraeil oat of the more simple and elementary by progressive spécialisation ¡mil integration ; unci, secondly, that the laws by means of which this formation takes place are not laws of association merely, but laws of organic combination and evolution. The growth of mental power means яп actual additoi of structure to tbo intimate, constitution of the centres of mind—a mmtal ori/nnitation in them; and mental derangement means disorder of them, primary or secondary, functional or organic.

Although I have declared the hemispherical ganglia to be pre-eminently the mmd centres, and although it is in disorder of their functions—in disordered intelligence, in disordered emotion,»nd in disordered will—that insanity essentially consists, it is nevertheless impossible to limit the study of our mental operations to the study of them. They receive impressions from every part of the body, and, there is reason to believe, exert an influence on every element of it: there is not an organic motion, sensible or insensible, which does not, consciously or unconsciously, affect them, and which they in turn do not consciously or unconsciously affect. So intimate and essential is the sympathy between all the organic functions, of which mind is the crown and consummation, that we may justly say of it that it sums up and comprehends the bodily life—that everything which is displayed outwardly iscontained secretly in the innermost. We cannot truly understand mind functions without embracing in our inquiry all the bodily functions and features.

I have already shown this in respect of motor functions, by exhibiting how entirely dependent for its cxprcssiou will is upon tho organised mechanism of the motor centres—bow, in effecting voluntary movements, it presupposes the appropriate education of the motor centres. Few persons, perhaps, consider what a wonderful art speech is, or even remember that it is an art which we acquire. But it actually costs us a great deal of pains 1о learn to speak; all the language which the infant has is to cry ; and it is only because we begin to learn to talk when wc are very young, and are so constantly practising, that we fort et how npecially we have had to educate our motor centres of speech. Here, however, wo como to another pregnant consideration: the acquired faculty of the educated motor centre is not only anecessary agency in the performance of a voluntary act, but I maintain that it positively enters iis a mental element into the composition of the definite volition ; that, in fact, the specific motor faculty not only acts downwards upon the motor nerves, thus effecting tho movement, but also acts upwards upon the mind centres, thereby giving to consciousness I ho conception of the suitable movement—the appropriate motor intuition. It is certain that, in ordor to execute consciously a voluntary act, wemnst have iu the mind a conception of the aim or purpose of the act. The will cannot act upon the separate muscles, it can only determine the result desired: and thereupon the combined contraction, in due force and rapidity, of the separate muscles takes place in a way that we have no consciousness of, and accomplishes the act. The infant directly it is born can suck certainly not consciously or voluntarily ; on the first occasion, at any rate, it енп have no notion of the purpose of its movements; but tho effect of the action is to excite in the mind the special motor intuition, and to lay the foundation of the special volition of it. Wc cannot do an act voluntarily unless wc know what we are going to do, and we cannot know exactly what we are going to do nntil we have taught ourselves to do it. This exact knowledge of tho aim of the act, which we get by experience, the motor intuition gives us.

The essential intervention of the motor intuition, which is, as it were, the abstract of tho movement, in our mental life, is best illustrated by the movements of speech, but is by no means peculiar to them. Each word represents a certain association and succession of muscular acts, and is itself nothing more than a conventional sign or symbol to mark the particular muscular expression of a particular idea. The word has not independent vitality; it differs in different languages; and those who are deprived of the power of articulate speech must make use of other muscular acts to exprime their ideas, speaking, as it were, in a dumb discourse. There is no reason on earth, indeed, why a person might not learn to express every thought which he can utter in speech by movements of his fing'rs, limbs, and body—by the silent language if gesture. The

movements of articulation have not, then, a special kind of connexion with the mind, though their connection is a specially intimate one; they are simply the most convenient for the expression of our mental states, because they are so numerous, various, delicate, and complex, and because, in conjunction with the muscles of the larynx and the respiratory muscles, they modify sound, and thns make audible language. Having, on this account, been always used as the special instruments of utterance, their connection with thought is most intimate; the Greeks, in fact, used the word Xoyoct to mean both reason and speech. But this does not make the relations of tho movements of speech to mind different fundamentally from the relations of other vol untary movements to mind ; and we should be quite as much warranted in speaking of a special faoulty of writing, of walking, or of gesticulating in the mind, as in speaking of a special faculty of speech there.

What is true of the relations of articulate movements to mental etates is tmo of the relations of other movements to mental states: they not only express the thought, but, when otherwise put in action, they can excite the appropriate thought. Speak the word, and the idea of which it is the expression is aroused, though it was not in the mind previously ; or put other muscles than those of speech into an attitude which is the normal expression of a certain mental state, and the latter isexcited. Most if not all men, when thinking, repeat internally, whisper to themselves, as it were, what they are thinking about ; and persons of dull and feeble intelligence cannot comprehend what they rend, or what is said to them sometimes, without calling the actual movement to their aid, and repeating the words in a whisper or aloud. As speech h:is becomo the almost exclusive mode of expressing our thoughts, there not being many gestures of the body which are tho habitual expressions of simple ideas, we cannot present striking examples of the powers of other movements to call up the appropriate ideas; yet tho delicate movements of the accommodation of the eye to vision at different distances seem really to give to the mind its ideas of distance and magnitude. Tío one actually sees distance and magnitude; he sees only certain signs from which he has learned to judge intuitively of them—tho muscular adaptations, though he is unconscious of them, imparting the suitable intuitions.

The esse is stronger, however, in regard to our emotions. Visible muscular expression is to passion what langnnge (or audible muscular expression) is to thonght. Bacon rightly, therefore, pointed out the advantage of a study of the forms of expression. "For," ho says, " tho linoaments of the body to disclose the disposition and inclination of the mind in general: but the motions of the countenance and patts do not only so, bnt do farther disclose the present humour and state of the mind or will." The muscles of the countenance are the chief exponents of human feeling, much of the variety of which is due to tho action of the orbicular muscles with the system of elevating and depressing muscles. Animals cannot lau^h, because, besides being incapable of ludicrous ideas, they do not possess in sufficient development the orbicular muscle of the lips and the straight muscles which act upon them. It is because of the superadded muscles and of their combined actions—not combined contraction merely, but consentaneous action, the relaxation of some accompanying the contraction of others —that tho human countenance is capable of expressing a variety of more complex emotions than animals can. Those who would degrade the body, iu order, as they image, to exalt, the mind, should consider more deeply than they do the importance of our muscular expressions of feelin;:. The manifold shades and kinds of expressitn which the lips present—their gibe--, gambols, and flashes of merriment; the quick language of a quivering nostril; the varied waves and ripples cf beautiful emotion which play on the human countenance, with the spasms of passion that disfigure it—all which we take such pains to embody fn art—are simply effects of muscular action, and might bo produced by electricity or any other stimulus, if wo could only apply it in suitable force to tne proper muscles. When tho eyo is turned upwards in rapt devotion, in the ecstacy of supplication it is for the same reason as it is rolled upwards in fainting, in sleep, in the egony of death; it is an involuntary act of the oblique m usclen, when the straight in uscles cease to act upon it. We pereeivo, then, in tho study of muscular action the reason why man looks np to heaven in | prayer, aud why ho has placed there the power

"whence cometh his help." A simple property of the body, ns Sir С Bell observes—the fact that the eye in supplication takes what is it« natural position when not acted upon by the will —has influenced our conceptions of heaven, onr religions observances, and the habitul expressions of our highest feelings.

(7b be continued.)

SCIEXCE FOR THE YOUNG.*

ВтTiierev. E. Kernan.clonoowes College.

{Continued from page 197.)

APP. XII. "Horizontal."—A body is said to be horizontal when its axis or base forms a right angle with the earth's radius. In Fig. 31 the line Ъ a b is horizontal in the true sense of the word.

App. XIII. The Plummet.—A weight hung freely, would fall, if allowed, along one of the radii, hence the line which holds it must bate the same direction. Tf, then, any elide tic-, of a body be parallel to that line, it must be perpendicular." A plummet or plumb line supplies a means of proving such parallelisms. This, so very common an instrument, scarcely requires description, Fig. 32. The bar A (of wood, iron, &c),

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has a cut or slight groove down the middle, and parallel to its edge a a. A small weight hangs from the top of the bar. The edge being placed upright along a body, if it be perpendicular, tho cord from which the weight hangs will liealoDg the groove ; if not it will lie one side or the other. It was this instrument which the French philosophers found at fault in Peru. The plumb line may also serve to show that a body is horizontal or not. For this purpose the cord groove is made at a right angle to edge to be applied at A, Fig. 33. Any deviation of the cord from the groove, will show that the body (its side, or axis, &c;) does not form a right angle with the earth's radius—is not horizontal.

Лрр. XIV. "Sun's Heat."—The mechanical theory of the sun's heat by percussion, depends upon the great force exerted by its enormous mass on small bodies in heavenly spaco.

Лрр. XV. Aérolites, Meteoric Stone .—Tho display of light and the fall of these upon the earth is caused by their coming within range of the earth's attraction. At different periods of each year tho belt in which they move is more or less approached ; hence the fixed dates of more or less action. liesides this yearly occurrence, certain peril ds of years, said to be 33, bring the earth much nearer for a short time, which produces, bv increased attraction, those gorgeous phenomena witnessed some years ago.

App. XVI. Earth, Different Gravitations,—In consequence of the earth not being л perfect sphere, the gravitatiou varies slightly in one place from another. Somo time ayo, too, a decreaso was observed near a mountain. This was accounted for as being caused by a lesser quantity of matter under the mountain. The same was observed at an earlier period in an open country near Moscow.

Pboblfms.

Prob. I. Why is the earth not seen to move to feathers falling? Show from formula.

H. Explain tho great cause of tho high and low tides, and what could havo been the reason of the extra high tide predicted for last October (186»)?

III. To what causes should be attribut td a

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