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stupendous conflagration of hydrogen gas-in plain English, that the star was 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 eclipse, are 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 idle to speculate upon it; but of the result of such a convulsion there can be no doubt whatever. The intensity of the Sun's rays would be increased some eight hundred fold, 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 we are unable to say whether they indicate a similar condition of things to that which obtained in the star in Corona or not, but that the spectrum of 7 Cassopeia (Vol. X., Map, p. 25) certainly resembles that of T Coronæ, the star of which we have been speaking, to a very considerable extent.

as the copper surface is so much diminished; thus
one cell will not give off so much current on short
circuit as in the usual form, but this is not of
much consequence. Fig. 39 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
Such a cell, pro-
principle of the bird fountain.
vided with two or three wire ganze cylinders, be-
tween the zinc and the porous jar, would pro-
bably furnish a constant current for a prolonged
period; this is called the Meidinger cell.
are many other modifications of the Daniell,
vaunted by their makers, but there are only two
calling for any remarks, because they are fre-
quently mentioned.

There

126. THE MINOTTO has been much lauded; it consists of a jar, at the bottom of which is a copper plate, fitted with a wire, this is covered with an inch of crushed sulphate of copper, and this again with a layer of silver sand, which is to act as the 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 4 in. 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 ELECTRICITY—ITS THEORY, SOURCES, several modifications, but all with the same

124.

(To be concluded.)

AND APPLICATION.

BY J. T. SPRAGUE.*
(Continued from page 196.)

are

The fluid surrounding the zinc may be the usual acid, or where great action is not needed, common salt, or sal ammoniac, and other substances 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 does not combine, but causes less 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 in. apart, as before. Charged with acid this gave 329, with sal ammoniac 30°, with common salt 27°, 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 some of the previous forms, but it would be erroneous to suppose that this signifies less force; the Daniell's cell has a higher force than the 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 sides 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 Daniell, while the latter continues to act steadily. This is exemplified by the following comparison of a good working Daniell's cell, which, at its utmost work, only gave 50°, with my powerful cell giving

81°, with different resistances interposed

Units 1 2 3 4
Daniell 50 27 20 13 11

Mine 81 33 21 14 11

It must be understood that the actual variation is much greater than 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 ENGLISH 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 362, and 37 a difference of 325, or 89 per cent., caused by the first unit of

resistance.

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result.

127. BOULAY'S cell, is another attempt to
overcome the evils of the Daniell.
It is very
peculiarly constructed, the 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 the 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 the 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 379, rising in two doing no work, after which it gave 259, falling to hours to 55. It was then set aside for a week, 20, and I find that it remains with a power of mental purposes, and would, no doubt, remain a about 20 to 16, so that it is very useful for experilong 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.

cell, with an addition for excess of local action 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 pound, we get the cost on the scale of gran equivalents, which is that I shall adopt, the ans of quantity or total current being one equivalent of any metal deposited or water decomposed Sulphuric acid equivalent

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of copper cell is easily explained as an extension
128. The theory of the action of the sulphate
The copper and brass imperial coins are ex-
of that shown in Fig. 36, p. 75. If we imagine tremely numerous, and of great interest. The
the porous partition in the middle and the two usual divisions of them-which are purely arbi-
right hand molecules to be sulphate of copper, trary-are into large, middle, and small, or 1st,

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2nd, and 3rd brass coins. The large brass is perhaps the sestertius; the second brass, when of brass, is the dupondius, and when of copper, the as "In the reign of Philip we find a coin breaking up ZnSO4, H2SO4, H2SO1,CuSO4Cu rather larger than the usual third brass, called The last line shows us that what occurs is that an the Philippus æreus, and in the time of Gallieatom of zinc is taken up and one of copper dis-nus, although the sestertii and dupondii cease placed, that the source of the force is simply the altogether as a regular series, there are small difference of affinity of sulphuric radical for zinc coins of brass, which we may suppose to repreand copper; the force yielded is equivalent to sent the as. In the reign of Diocletian a new the heat zinc would give while precipitating copper from its sulphate, and is really the differ- coin of copper appeared, termed the follis. This ence between the internal force necessary to the and a smaller coin (the assarius), both of which existence of sulphate of copper, and that bound gradually decrease in size, continue till the reign or latent in sulphate of zinc. It is probable, of Honorius." (Madden.) however, that it is only at the last molecule that copper sulphate forms part of the circuit if there is free acid present, but that does not affect this principle, which sets the action before us far more comprehensibly than the idea that water, or even acid is decomposed, and completes the circuit, while the nascent hydrogen merely reduces the copper chemically.

Copper or brass medallions were made of a larger size than the first brass coins. They were not struck for circulation as money, but probably served the same purpose as 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 tɔ make them of great value. With Gallienus, A.D. 129. I have dwelt thus fully on this form, be- 268, they terminate. Among the scarce and incause of its importance, both practical and theo-teresting types are the following:-One of Livia retical, and it only remains now to show the cost with her bust, and IVLIA AVGVSTA GENETRIX of its working; this will be the same as the simple ORBIS. This latter title was conferred on her by

NICVS.

the Senate. Coins of Drusus, commemorating his conquest of the Germans, hence called GERMAOne of Claudius, with reverse a triumphal arch, and DE BRITANNIS, relating to his triumphs in Britain. Another of Vespasian, bearing a female figure of Judea, seated weeping under a palm tree; inscription, IVDAEA CAPTA referring to the conquest of Judea and destruction of Jerusalem, A.D. 70. Others of Titus, similar, and eommemorating the same events. One of Trajan smiting a Dacian foe. Others with fine portraits of Antoninus Pius, Marcus Aurelius, the two Faustinas. The famous medallion of Commodus with BRITANIA. The VICT BRIT. of Geta, &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 been found With the small -Constantine, and his sons. 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 The reduction coins of the same denominations.

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from 84 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. 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. 251-254), 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 cententionalis, which is most likely the silver coin, which weighs a little less than fifty grains: when it was first issued is not certain. (Madden.)

The series of Imperial silver is by far the cheapest and most easily obtained, besides 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 which we have selected for illustration is a silver denarius of Tiberius Cæsar, Emperor from A.D. 14 to A.D. 37. 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, Cæsar's." The coin has, obverse, the bust of Tiberius Cæsar. Inscription: TI. CESAR, DIVI. AVG. F. AVGVSTVS; showing the name Caesar at full

length. Reverse, a female figure seated. PONTIF. 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 60 out of a pound, and Constantine the Great issued a new coin, the solidus, instead of the aureus. 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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We engrave (No. 6) an aureus of Titus, Emperor from A.D. 79 to A.D. 81. Obverse, laureated bust. IMP. TIIVS. CAES. VESPASIAN. AVG. P.M. Reverse, a dolphin twined round an anchor. P. IX. IMP. XV. COS. VIII. P. P. Weight 113 grains. Gold and silver medallions of large size were struck, probably for the same purposes as the copper ones.

TR.

The abbreviations of some of the titles, etc., are as follow:

:

AED. CVR., Edilis Curulis.
AED. PL., Edilis Plebis.
AVG., Augustus.
AVGG., Two Augusti.
AVGGG., Three Augusti.
C., CAE., or CAES., Cæsar.
CAESS., Cæsares.
CEN., Censor

COS., Consul; COSS., Consules.
D., Divus.

DAC., Dacicus.

DES. or DESIG.; Designatus.
D. F., Divi Filius.

DICT. PERP., Dictator Perpetuus.
DIV., Divus.

D. N., Dominus Noster.

F., Filius or Felix.

FEL., Felix.

FL., Flavius.

GERM., Germanicus.

IMP., Imperator; IMPP., Imperatores. III. VIR., Triumvir.

OB. C. S., Ob Civis Servatos.

P. F., Pius Felix.

P.M. or PONT. MAX, Pontifex Maximus.
P. P., Pater Patriæ.
PROC., Proconsul.
PROP., Proprætor.

S. C., Senatus Consulto.

S. P. Q. R., Senatus Populusque Romanus.
TI., Tiberius.

TR. P. or TRIB. POT., Tribunitia Potestate; having Tribunitian power.

VOT., Votis., &c., &c.

(To be continued.)

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 the 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 he 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, had he been gazing on so beautiful a country. The contrast 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 George Robins, if he 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 we 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 I 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 sightly 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 I am afraid, of sometimes making its anatomical details 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, that this love 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-acquired source of pleasure, for it will, before very long, fully explain to us 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.

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THE SCENERY AND GEOLOGICAL STRUCTURE OF A COUNTRY. The scenery of a country will depend in a great HE subject I have chosen is to some extent measure on the shape of the ground: whether it Thow to many, and I think it promises to bring is hilly, mountainous, flat, or traversed by deep with it a new source of intellectual pleasure to or broad valleys. When we wish to see the conus, in that it may be made a source of agreeable nection between scenery and geology, we mental exercise. I can say, from my own ex-first see how it had its appearance given to it. perience, that it has enabled me to pass many a Hills and mountains, valleys and deep gorges long and tedious railway journey much more seem very striking to us, but if we look at them pleasantly than I could have passed it had I been in comparison with the size of the whole earth, ignorant of the simple truths I am about to place they appear as little bulges on its surface. Now, before you. We know that tastes and pursuits of the earth is enveloped in a thin external shell, this sort are powerful engines of enlightment and which is made up of a number of substances, such truth; and that they tend very much to keep us as limestones, sandstones, clays, gravels, &c., all out of that mischief which, the prophet tells us, is of which are known geologically under the name always ready for idle hands into. The necessary of rocks; and a very large proportion of these knowledge for this recreation lies within the reach rocks were originally formed of sand, mud, and of every one. It is not like going into the full soft sediment, which was carried down by rivers study of Geology-that takes a lifetime. This to the sea, and allowed to fall to the bottom. Thus pleasant application of science requires little more the sea-bottom was gradually raised up until at than a good use of the eyes, and plain, homely, last it was elevated into dry land. Now it was while this elevating process was going on that the common sense. land first began to assume its present shape. We need not for our present purpose concern ourselves with the way in which the sediment was brought, or where it came from; I ask you to

The delight in natural scenery and the power

A lecture delivered at St. George's Hall, by A. H. GREEN, Esq., M. A, Cambridge, FG,S. (of her Majesty's Geological Surveys), March 20, 1870.

believe me when I tell you that the sediment was carried into the sea, 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 sub-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 wearing-away action 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 subaërial 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 a 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, trench-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 earth's surface

have 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 out of the quarry and takes it to the sculptor, who carves 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 the 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 mountains, 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 subaerial 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 might almost ride 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.

FIG

(To be concluded)

KEYES' IMPROVED WAGGON WHEEL. IG. 1 is a perspective view of the central portion 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 section of the same, revealing the entire construction of the hub, and the manner of inserting and fastening the spokes. A, Figs. 1 and 2, is 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

wood hub, the inner end of the wood hub being made somewhat smaller than the recess in A, as shown.

MECHANICAL MOVEMENTS. (Continued from page 200.) THREE-LEGGED pendulum escape

The internal wooden hub receives the axle box, 106. ment. The pallets are formed in an

which is first driven into the wood hub B as tightly as possible, and when the axle box is

FIG. I

driven in and wedged, the wood hub is forced outward, so that it enters and fills every part of the recess, and the shoulders of the recess prevent its moving or working loose. Previous to driving in the axle box, the wooden hub B is also fastened to the iron at the bottom of the spokes subsequently to be inserted.

The external iron hub has two very stout flanges which laterally support the tenons of the spokes when the latter are driven, as shown in both en

gravings; each alternate spoke C 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 retained in the hub 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 MECHANIC MUTUAL IMPROVEMENT SOCIETY.-MANCHESTER BRANCH.

A SECOND meeting was held on May 16, and the officers to the society elected, with a committee 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 to the Parallelogram of Forces," by the Secretary. The meeting to be held at the Mancheeter Mechanics' Institution, David-street, on June 1, at 8 p.m., precisely

"A New Solution

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 s shown in operation on the upper pallet.

107. A modification of the above with lo stopping teeth D and E. A and B are the pallet

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, I, which receives impulse only during the vibra tions 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, attached to the pendulum. As the pendalum returns to the right, the click, which oscillates on a pivot, will be pushed aside by the lever.

109. Mudge's gravity escapement. The pallets A 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 out 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 centre 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 A B C and a be 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 E on the other pallet.

112. Bloxam's gravity escapement. The pallets are lifted alternately by the small wheel, and the stopping is done by the action of the stops A and B on the larger wheel. E and F are the 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.

114. Lever chronometer escapement. In this the pallets A B 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.

115. 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.

116. Mercurial compensation pendulum. A glass jar of mercury is used for the bob or weight. 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 the same.

117. Compound bar compensation pendulum. C is a compound bar of brass and iron or steel, brazed together with brass downwards. As brass expands more than iron, the bar will bend upward as it gets warmer, and carry the weights WW 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.

attached at its outer end to a fixed stud R, and 118. Watch regulator. The balance-spring is 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. T. Brown, Editor of the mercan Artisan.

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duced.

(To be continued.)

MECHANICAL MOVEMENTS.

ON THE RELATIONS BETWEEN BODY memory; but which of us finds it necessary to

T

AND MIND.*
LECTURE I.

to turn on a fixed ring concentric with staff of state has been completely organised, it is revived | their impressions in sensori-motor action, so, after balance, and the spring only vibrates between without consciousness, and takes its part auto- the complex interworking and combination of this neutral point and staff of balance. By mov-matically in our mental operations, just as a ideas in the hemispherical ganglia, there is, in ing lever to the right, the curb-pins are made to habitual movement does in our bodily activity. like manner, a reaction or desire of determination reduce the length of acting part of spring, and We perceive in operation here the same law of of energy out wards, in accordance with the fundathe vibrations of balance are made faster; and by organisation of conscious acquisitions as uncon- mental property of organic structure to seek what moving it to the left an opposite effect is pro-scious power, which we observed in the functions is beneficial and shun what is hurtful to it. It is of the lower nerve centres. A child, while learn this property of tissue that gives the impulse ing to speak or read, has to remember the mean- which, when guided by intelligence, we call ing of each word, must tediously exercise its volition, and it is the abstraction from the particular volition which metaphysicians personify remember the meanings of the common words as the will, and regard as their determining agent. which we are daily using, as we must do those of Physiologically, we cannot choose but reject the will; a foreign language with which we are not very volition we know, and will we know, but the will, familiar? We do remember them, of course, but apart from particular acts of volition or will, we it is by an unconscious memory. In like manner, cannot know. To interpose such a metaphysical to call to mind each note; but the skilful player would bring us logically to the necessity of intera pupil, learning to play the pianoforte, is obliged entity between reflection and action thereupon, goes through no such process of conscious remem-posing a similar entity between the stimulus to brance; his ideas, like his movements, are auto- the spinal cord and its reaction. Thus, instead matic, and both so rapid as to surpass the rapidity of unravelling the complex by help of the more To my mind, there are incontrovertible reasons to tions concerning the complex. As physiologists of succession of conscious ideas and movements. simple, we should obscure the simple by speculaconclude that the organic conditions of memory we have to deal with volition as a function of the are the same in the supreme centres of thought as supreme centres, following reflection, varying in they are in the lower centres of sensation and of quantity and quality as its cause varies, strengthreflex action. Accordingly, in a brain that is not ened by education and exercise, enfeebled by disdisorganised the org nic registrations are never use, decaying with decay of structure, and always actually forgotten, but endure while life lasts; no needing for its outward expression the educated Consciousness, it is true, may be impotent to have to deal with will, not as a single undecomwave of oblivion can efface their characters. agency of the subordinate motor centres. We recall them; but a fever, a blow on the head, a posable faculty unaffected by bodily conditions, poison in the blood, a dream, the agony of drown- but as a result of organic changes in the supreme ing, the hour of death, rending the veil between centres, affected as certainly and seriously by diswill sometimes call vividly back, in a momentary order of their centres. Loss of power of will is our present consciousness and these inscriptions, order of them as our motor faculties are by disflash, much that seemed to have vanished from one of the earliest and most characteristic sympthe mind for ever. In the deepest and most secret toms of mental derangement; and, whatever may recesses of mind, there is nothing hidden from the have been thought, in times past, we know well thus sometimes accidentally revealed; so that it spirit that has laid its hands upon the will, but individual self, or from others, which may not be now that the loss is not the work of some unclean opening of the book at the day of judgment shall might well be that, as De Quincy, surmised, the the direct effect of physical disease. be the unfolding of the everlasting scroll of

(Continued from page 199.) AKE, for example, the so-called faculty of memory, of which metaphysicians have made so much, as affording us the knowledge of 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 sensory ganglia, obviously imply the existence of memory, which is 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 occasions of similar impressions. A ganglionic centre, whether of mind, sensation, or movement, which was without memory, would be an idiotic centre, incapable of being taught its functions. In every nerve-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 on the constitution for the rest of life. We may forget it but it will not forget us, though, like the memory of an old man, it may fade and become faint with advancing age.

The manner in which the scar of a

memory.

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.
As it is with memory, so it is with voliti n,
Memory is the organic registration of the effects which is a physiological function of the su-
of impressions, the organisation of experience,
and to recollect is to revive this experience-to preme centres, and which, like memory, becomes
more unconscious and automatic the more com-
call the organised residue into functional activity.pletely it is organised by repeated practice. It is
The fact that memory is accompanied by con-
sciousness in the supreme centres does not alter not man's function in life to think and feel only;
the fundamental nature of the organic processes of some kind-in word or deed.
his inner life he must express or utter in action
that are the condition of it. The more sure and
Receiving the
perfect, indeed, memory becomes, the more uncon-
impressions from nature, of which he is a part,
scious it becomes; and when an idea or mental he reacts upon nature intelligently, modifying it
in a variety of ways; hus nature passes through
human nature to a Ligher evolution. As the
spinal cord reacts to is impressions in excito-
motor action, and as the seasory centres react to

Two lectures delivered at the Royal College of Physicians in 1870. By HENRY MAUDSLEY, M.D., F.R.C.P., Professor of Med cal Jurisprudence in University College, London,

But I must pass on now to other matters, without stopping to unfold at length the resemblances between the properties of the supreme centres and those of the lower nerve centres. We see that the supreme centres are educated, as the other eentres 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 are successively acquired through the gateways of the senses, are blended and combined and grouped in a complexity that defies analysis, the organic combinations being the physiological conditions of our highest mental operations-reflection, reasoning, and judgment. Two leading ideas are ought to grasp and hold fast: first, that the co m plex and more reco: dite phenomena of mind we

(To be continued.)

SCIENCE FOR THE YOUNG.*

(Continued from page 197.)

APP. XII.

formed out of the more simple and elementary by movements of articulation have not, then, a special" whence cometh his help." A simple property
progressive specialisation and integration; and, kind of connexion with the mind, though their of the body, as Sir C. Bell observes the fact
secondly, that the laws by means of which this connection is a specially intimate one; they are that the eye in supplication takes what is its
formation takes place are not laws of association simply the most convenient for the expression of natural position when not acted upon by the will
merely, but laws of organic combination and our mental states, because they are so numerous, has influenced our conceptions of heaven, og
evolution. The growth of mental power means various, delicate, and complex, and because, in religious observances, and the habitul express.c
an actual addition of structure to the intimate conjunction with the muscles of the larynx and of our highest feelings.
constitution of the centres of mind-a mental the respiratory muscles, they modify sound, and
organisation in them; and mental derangement thus make audible language. Having, on this
means disorder of them, primary or secondary, account, been always used as the special instru-
functional or organic.
ments of utterance, their connection with thought
Although I have declared the hemispherical | is most intimate; the Greeks, in fact, used the
ganglia to be pre-eminently the mind centres, and
although it is in disorder of their functions-in
disordered intelligence, in disordered emotion, and
in disordered will-that insanity essentially con-
sists, 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 essen-
tial is the sympathy between all the organic func-
tions, of which mind is the crown and consumma-
tion, that we may justly say of it that it sums up
and comprehends the bodily life-that everything
which is displayed outwardly is contained secretly
in the innermost. We cannot truly understand
mind functions without embracing in our inquiry
all the bodily functions and features.

word Aoyor to mean both reason and speech. BY THE REV. E. KERNAN, CLONGOWES COLLEGE
But this does not make the relations of the move-
ments of speech to mind different fundamentally
from the relations of other voluntary movements
to mind; and we should be quite as much war-
ranted in speaking of a special faculty of writing,
of walking, or of gesticulating in the mind, as in
speaking of a special faculty of speech there.

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

B FIG. 31

a

App. XIII. The Plum met.-A weight hung freely, would fall, if allowed, along one of the radii, hence the line which holds it must have the same direction. If, then, any slide &c., of a body be parallel to that line, it must be A plummet or plumb line of proving such paral lelisms. This, 80 very common an instrument, scarcely requires description, Fig. The bar A (of wood, iron, &c.),

a means

FIG. 32

FIC.22

What is true of the relations of articulate movements to mental states is true 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 perpendicular." is excited. Most if not all men, when thinking, repeat supplies internally, whisper to themselves, as it were, what they are thinking about; and persons of dull and I have already shown this in respect of motor feeble intelligence cannot comprehend what they 32. functions, by exhibiting how entirely dependent read, or what is said to them sometimes, without for its expression will is upon the organised calling the actual movement to their aid, and mechanism of the motor centres-how, in effect-repeating the words in a whisper or aloud. As ing voluntary movements, it presupposes the ap- speech has become the almost exclusive mode of propriate education of the motor centres. Few expressing our thoughts, there not being many persons, perhaps, consider what a wonderful art gestures of the body which are the habitual exspeech is, or even remember that it is an art pressions of simple ideas, we cannot present which we acquire. But it actually costs us a striking examples of the powers of other movegreat deal of pains to learn to speak; all the ments to call up the appropriate ideas; yet the language which the infant has is to cry; and it delicate movements of the accommodation of the is only because we begin to learn to talk when we eye to vision at different distances seem really to are very young, and are so constantly practising, give to the mind its ideas of distance and magnithat we forget how specially we have had to tude. No one actually sees distance and magnieducate our motor centres of speech. Here, how-tude; he sees only certain signs from which he ever, we come to another pregnant consideration has learned to judge intuitively of them-the the acquired faculty of the educated motor centre muscular adaptations, though he is unconscious has a cut or slight groove down the middle, and is not only a necessary agency in the performance of them, imparting the suitable intuitions. parallel to its edge a a. A small weight hangs of a voluntary act, but I maintain that it posi- The case is stronger, however, in regard to our from the top of the bar. The edge being placed tively enters as a mental element into the com- emotions. Visible muscular expression is to pas- upright along a body, if it be perpendicular, the position of the definite volition; that, in fact, the sion what language (or audible muscular expres- cord from which the weight hangs will lie along specific motor faculty not only acts downwards sion) is to thought. Bacon righly, therefore, the groove; if not it will lie one side or the other. upon the motor nerves, thus effecting the move-pointed out the advantage of a study of the forms It was this instrument which the French philoment, but also acts upwards upon the mind of expression. "For," he says, "the lineaments centres, thereby giving to consciousness the con- of the body to disclose the disposition and inclina-sophers found at fault in Peru. The plumb line ception of the suitable movement-the appropriate tion of the mind in general; but the motions of may also serve to show that a body is horizontal or not. For this purpose the cord groove is made motor intuition. It is certain that, in order to the countenance and parts do not only so, but do at a right angle to edge to be applied at A, Fig. execute consciously a voluntary act, we must have further disclose the present humour and state of 33. Any deviation of the cord from the groove, in the mind a conception of the aim or purpose the mind or will." The muscles of the counteof the act. The will cannot act upon the separate nance are the chief exponents of human feeling, will show that the body (its side, or axis, &c.) muscles, it can only determine the result desired; much of the variety of which is due to the action does not form a right angle with the earth's and thereupon the combined contraction, in of the orbicular muscles with the system of ele-radius-is not horizontal. due force and rapidity, of the separate muscles vating and depressing muscles. Animals cannot takes place in a way that we have no laugh, because, besides being incapable of ludiconsciousness of, and accomplishes the act. crous ideas, they do not possess in sufficient deThe infant directly it is born can suck velopment the orbicular muscle of the lips and the App. XV. Aerolites, Meteoric Stone.-The certainly not consciously or voluntarily; on the straight muscles which act upon them. It is first occasion, at any rate, it can have no notion because of the superadded muscles and of their display of light and the fall of these upon the of the purpose of its movements; but the effect combined actions-not combined contraction earth is caused by their coming within range of At different periods of of the action is to excite in the mind the special merely, but consentaneous action, the relaxation the earth's attraction. motor intuition, and to lay the foundation of the of some accompanying the contraction of others each year the belt in which they move is more or special volition of it. We cannot do an act that the human countenance is capable of ex-less approached; hence the fixed dates of more or voluntarily unless we know what we are going to pressing a variety of more complex emotions than less action. Besides this yearly occurrence, cerdo, and we cannot know exactly what we are animals can. Those who would degrade the tain periods of years, said to be 33, bring the going to do nntil we have taught ourselves to do body, in order, as they image, to exalt the mind, earth much nearer for a short time, which proit. This exact knowledge of the aim of the act, should consider more deeply than they do the duces, by increased attraction, those gorgeous which we get by experience, the motor intuition i portance of our muscular expressions of feel. phenomena witnessed some years ago. gives us. ing. The manifold shades and kinds of expression which the lips present-their gibes, gambols, and flashes of merriment; the quick language of a quivering nostril; the varied waves and ripples of beautiful emotion which play on the human countenance, with the spasms of passion that disfigure it-all which we take such pains to embody in art-are simply effects of muscular action, and might be produced by electricity or any other stimulus, if we could only apply it in suitable force to the proper muscles. When the eye is Prob. I. Why is the earth not seen to move to turned upwards in rapt devotion, in the ecstacy feathers falling? Show from formula. of supplication it is for the same reason as it is II. Explain the great cause of the high and rolled upwards in fainting, in sleep, in the agony low tides, and what could have been the reason of of death; it is an involuntary act of the oblique the extra high tide predicted for last October muscles, when the straight muscles cease to act upon | (1869) ? it. We perceive, then, in the study of muscular III. To what causes should be attributed a action the reason why man looks up to heaven in The copyright of this series of articles is reserved prayer, and why he has placed there the power by the Author.

The essential intervention of the motor intuition, which is, as it were, the abstract of the 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 express 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 fingers, limbs, and body-by the silent language of gesture. The

App. 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 space.

App. XVI. Earth, Different Gravitations.-In consequence of the earth not being a perfect sphere, the gravitation varies slightly in one place from another. Some time ago, too, a decrease was observed, near a mountain. 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.

This was accounted

PROBLEMS.

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