SCIENCE FOR THE YOUNG. tion thus obtained available, and sufficiently identities the specimen. As the collector pursues his investigations month after month, he will find BY THE REV. E. KERNAN, CLONGOWES COLLEGE. his senses becoming educated to a delicacy of touch and fineness of perception that cannot fail to be a source of pride and gratification to him. He whose attention would not at first be diverted caterpillar-ridden tree to the ragged leaves of a caterpianty the slight convexity of outline on twig or leaf caused by the presence of a small insect, or the extremity of a branch cleanly cnt by a pruner-beetle. In the course of his observations he will be amused by the imitative shapes and colours of many forms of insect life, and will frequently be deceived by the Curculios, who successfully simulate buds and bits of bark. The caterpillars of some of the moths resemble so closely cylindrical twigs, as many of the Loopers (Geometrida); scales of rough or smooth bark, as the Hag-moth (Limacodes pithecium) and the Lappet-moths (Gastropacha veleda and Americana). Some of the beetles, as the Crytocephali and Histers, closely resemble seeds, as do certain bugs, among them Corimelaena, and the two latter suggest such kinship as to cause them almost invariably to frateraise in the cabinet of the amateur. These singular resemblances are called mimet e forms; and, existing everywhere in nature, even if they have no higher significance and serve no better purpose, educate our perceptive powers to a degree undreamed of by the careless horde of money worshippers. During the active season of the insect year the collector should make it a rule never to stir abroad without a cork-stopped vial half filled with alcohol, for the temporary deposit of beetles, ants, or the larva or pupe of any insects that it may be desirable to preserve in this way. The only insects that are irrecoverably injured by a few days' immersion in pure alcohol are the butterflies and moths. For these a small cork or pith-lined pocket-box, of convenient form, and full 1 in. in depth, containing a few insect pins of various sizes, is indispensable, and should be 2 constant companion. Upon a premeditated excursion of a day or more in duration, the collector will naturally provide more extensive means of transportation, such as jars of alcohol, a vial of chloroform, a number of old envelopes a large box slung on side with straps, and a proportionate stock of pins. Some collectors continually carry, in a pocket made for the purpose, a wide-mouthed vial, like a chemist's test-tube, "of the same size all the way up," containing at the bottom a few grains of cyanide of potassium, which is kept in place by a wad of cotton, felt, or thick cloth, neatly pressed down upon it. This prevents the cyanide, which is a deadly poison, from touching or soiling any delicate insect, and allows the powerful vapour to destroy, as it does almost instantly, the life of any insect that may be inclosed in the prepared vial. The permanence of this poison (its virtue enduring for a twelvemonth or more), its cleanliness, and cheapness, render it perhaps the most convenient and desirable "life annihilator." It is, perhaps, unnecessary to mention that the vial should be kept tightly corked, and that the insect should remain therein not much more or less than ten minutes. A vial, lin. in diameter and 4in. in length, made of strong glass, is the most desirable size. Some collectors carry a small vial of chloroform, through the cork of which passes a very small tube of metal; what is called by jewellers "hollow wire," of minute aperture, is used for this purpose. This instrument is used for conveying a limited quantity of chloroform to the spiracles of the insect, without deluging and damaging much of its plumage, if furnished therewith. Ether, as well as chloroform, is sometimes used in 1 eu of the cyanide, but it has to be continually supplied from another reservoir. In some countries bruised laurel leaves are placed in the bottom of the vial, or a small packet of them pinned in a corner of the collecting-box, inclosed in a little bag or wisp of loosely-woven cloth, such as lace, book-muslin, &c. All of these poisons act at first only as anesthetics, or stupifiers, and should be continued in use sufficiently long to destroy vitality, or to prevent th estruggles of the insect; for by these struggles it injures itself, as well as its companions, after being pinned in the collecting box.-The American Entomologist nad (Continued from page 269.) CHAPTER III. SI-FORCES APPLIED TO A POINT. forces. From their conditions of equilibrium, To have there must be at least two that of many forces is easily drawn. Forces (two) may act on a body, opposite or at an angle. No. 1. Laws. These include any number of forces in either of the possible positions. Some laws may appear too self-evident to be mentioned, still they are not the less true laws. Law I. Two opposite forces are in equilibrium when they are equal one to the other. Equilibrium is otherwise impossible. Law II. Many opposite forces are in equilibrium when their algebraical sum is equal to zero. Suppose three forces PQR, they are in equilibrium when P+Q - R = 0. Any number connected by the signs + and (as they are at one or other side of the body) and reducible to zero, are in equilibrium. Law III. Two forces at an angle cannot be in equilibrium without at least a third. It is not possible that two forces acting at an angle on a body be in equilibrium; the body must move, until they come into a straight line. Law IV. Two forces at an angle may be replaced by a single force, represented by the diagonal of a parallelogram constructed on the two forces. The lines which represent the two forces acting here on a body, are supposed to have each a length proportionate to the intensity of the force which each represents. When the parallelogram which those lines admit is completed, the diagonal from the point of application_represents in intensity and direction the resultant of the two forces. Law V. Two forces at an angle will be kept in equilibrium by a third force, equal and opposite to their resultant. Law VI. Many forces in the same plane may be reduced by "composition" to two, which can be equilibriated by Law V. Several forces applied to a point can be combined two by two, so as to leave one pair, the resultant of which can be stopped by an equal and opposite force. The whole system is then in equilibrium, Law VII-Many forces in different planes can be reduced to a resultant, which is equilibriated by Law I. Several forces in different planes and directions can be so combined by one or other of the preceding laws that that there be left but one force. No. II.-PROOFS. position; it is not possible, without putting a weight at (a), to have equilibrium at any angle. Law IV. This law contains the famous proposition known by the title of "The Parallelogram of Forces." Its importance is best evinced by the fact that it may be called the foundation of all mechanical science. Of the parallelogram some experimental. The latter in tical proofs, ad of forces there are many mathematical much to the dynamical view of the question to be spoken of in statics. The elementary mathematical proofs are long, tedious, and not perhaps very satisfactory. But there is a simple yet solid proof based upon a necessary consequence of inertia, which proof will not tax too much the mind or patience of the student. The consequence or principle to be admitted is as follows:-"A force, if allowed to act, must satisfy all its requirements." In plain terms, as before, whatever the force wants to effect with regard to any position in space that it must have effected before, it will cease to act. When such has been accomplished, the force is exhausted-has done its work fully. Inertia being a perfect indifference to change of state when the body has acquired motion from a force, it will allow that force to realise all its requirements if no external force can interfere. Therefore the body shall move to such a point in space es will completely exhaust the requirements of the force. With this principle the proof of the parallelogram of forces is easy and satisfactory. There are two main points to be proved. First, that the diagonal represents the "direction which the body would follow if the forces were allowed to act; secondly, that it represents the joint-action or "intensity "of the two forces. The whole argument may be got into three short points. 1. The forces P and Q (Fig. 56) applied to the body A, if allowed to act, must satisfy all their requirements. The point S of the parallelogram is the only point in space at which the requirements will be satisfied. Therefore the body must be found at S, when the forces have satisfied their require ments. 2. The body must have followed the straight line A S(the diagonal) in its passage to the point S, for two points in space are sufficient to determine the direction of a straight line. The starting point A and arrival point B are determined. That the body must take a straight line is evident; first, because the forces are supposed to act but for an instant; secondly, even supposing the action of the forces continuous, their relative proportion must be maintained. Now, instantaneous force is admitted to produce a straight line, and the slightest deviation from the diagonal must destroy the relative proportion of the forces, for nothing exists to make them act otherwise than parallel to their original direction. Law I. The body is equally acted upon at both sides; there is no cause to determine motion in one or other direction. As nothing tends to overcome the inertia of the body, it is at rest. Experi-Q, indicate by its length the intensity of their 3. The line AS must, compared with P and mentally, Fig. 55. The two forces P and Q acts Law II. As the sum = 0, algebra teaches that the + - side of the equation. Therefore the forces are in the condition of Law I, for a number of forces, in the same direction, act as one equal to their sum. Experimentally, a number of weights taken at random are divided into two parts, M and N, calculate the sum of each part. If M N = 0, the two parts may be hung to the weights p q, Fig. 55, without disturbing equilibrium. It M - N = n (some indefinite quantity) there will be an effect produced on A, it will move at least, if the differences (n) be considerable. THERE is, near Grenoble, what guide-books call a Law III. Both forces acting more or less in burning fountain. Prof. Raoult, who has lately the same direction, there is nothing to prevent visited this phenomenon, has published a short account the body from yielding to their joint action. Exof it. It is an emanation of mixed gases. The chief constituent is marsh gas, and there are small quanti-perimentally, draw down the body A, Fig. 55, let go gently it is drawn up to the horizontal Botanist. ties of carbonic acid and of olefiant gas. joint action; for, in representing forces by lines. their intensities are shown by length-that is, the distance from the beginning to the end of a line pictures relatively the full strength and the complete exhaustion of the forces. Now this is exactly what the diagonal A S exhibits. To complete this argument, there now remains to be proved one proposition contained in point 1, which, as it is the chief, so it is the longest, in demonstration. Still it is not difficult if taken quietly and by parts. The proposition is: "The point S of the parallelogram is the only point in space at which the requirements can be satisfied." It will be readily admitted that if the point S satisfies the requirements for one position, all the requirements for other positions must be satisfied. For greater simplicity, the lines representing the forces will be taken as the positions to be examined; and the three possible sorts of angles which these lines can make (right angle, acute, and obtuse) will make three cases, to be treated separately. P FIG. 51 R Case I. Right-angle (Fig. 57). The requirement of the force P as regards the position M Q. is to place the body M at a distance from M Q equal to the line MP; for MP being perpendicular on M Q, the length of the force, P itself shows the re- MO quirement. Now at the point R the body M is at a distance from MQ equal to M P, because (perpendicular between parallels being equal) QR MP; therefore R satisfies the requirement of P. On the other side the require ments of Q as to the position M P, is to place the body M at a distance from M P equal to MQ for M Q shows the requirement of Q, as M Pthat of P. Now at R the body is at the distance equal to M Q, as PR = M Q. The point R the efore satisfies the requirements of both P and Q. But there is no other point along the diagonal, along the sides, or in space in general which will satisfy one or the other; any point will satisfy these requirements. Various points for instance, along P R will do for P, any point on QR will do for Q; none will do for both, as along the diagonal none would do for either. Therefore R is the only point which will satisfy the requirements of the two forces. Case II. M Acute angle (Fig. 58). The require FIG. 58 R ment of the force P as regards the position M Q, is to place the body M at a distance from M Q, equal to P p, which shows the requirement being the perpendicular on M Q from the exhaustion point of P. Now at R the body is at the required distance, as R A, the perpendicular from R on the prolongation of M Q being equal to PP; therefore P is satisfied. The requirement of the force Q in regard of the position M P, is to place the body M at a distance from M P equal to Q q, the requirement perpendicular of Q. Now at R the body is at the required distance; Rr, the perpendicular on the prolongation of M P, being equal to Q 4. Again, therefore, R satisfies the requirements of P and Q, and no other point will do so, &c., same reasoning as in Case I. Case III. Obtuse angle (Fig. 59). The P M FIG. 59 B P FIG. 66 R the whole figure into "the acute angle, (this is the chief position shown; the right angle is in light lines; the obtuso angle in dotted lines). the small black rods fall into position as P p and its parallel R A., the long black rods may be raised up to the perpendicular as Qq and R r, and pinned there. Draw pins and shift to the obtuse angle. The small black rods, fall again into position, as in the dotted figure, and the long ones can be pinned below, as Qq and Rr. The model may be made to range from the most acute to the most obtuse angle. THE (To be continued.) SOCIETY OF ARTS ART-WORK- HE Council of the Society of Arts intend in Ttheir Art Workmanship competition of next year to suspend for a time the form hitherto adopted in offering prizes for art workmanship, believing the change is likely to be beneficial to the object the Council have at heart, viz., to see re-the art workmen of the United Kingdom occupying a good position in the coming International Exhibition in comparison with those of other countries. With this view the Council have decided upon offering a series of rewards for special excellence on the part of all concurring in the satisfactory production of works of industry of the highest character. They consider that they can most effectually ensure their object by offering to manufacturers the highest distinctions they have it in their power to confer, and to workmen liberal money premiums. They desire to obtain, from those who may be willing to compete for the prizes they offer, specimens of art manufacture, quirement of the force P as to the posti which will have to be sent to the society's rooms is to place the body M at a distance from M Q by the 14th of January, 1871. These will be imequal to P p, the perpendicular from the exhaus-mediately judged upon their merits, and the pretion of P on to the prolongation of M Q. Now at miums enumerated below will be awarded. An R the body is at the required distances, R A being endeavour will be made to effect arrangements by equal to Pp. The requirement of Q as regards means of which every object receiving a premium, M P is to place the body M at a distance from or selected for the distinction of being exhibited, M P equal to Qq, the perpendicular from the exhaustion of Q on to M P. Now at R the body is at the required distance, Rr being equal to Qg, therefore R satisfies both P and Q, &c. Finish as in Case I. Following the same train of reasoning, it could be shown that for any position at R the requirements will be fully satisfied. But there is no need of seeking the requirements for other positions, for the points which is necessary for one pair must satisfiy all. the manufacturers may receive the gold or silver No object involving combined labour for its production will be eligible for reward unless accompanied with the names of all those engaged in its production, to the most meritorious of whom-whether their works may be exhibited in the rooms of the society or in the International Exhibition-every effort will be made by the Council to give publicity and attract attention. TESTING THE DUTY OF STEAM AT a recent meeting of the Polytechnic Asso ciation of the American Institute, Dr. Van der Weyde gave an explanation of some of the most approved means of testing the duty of steam engines. As the engine may be considered simply as a system of mechanism for changing heat into motion, economy of fuel is the poin most to be considered in any estimate of the utility or working value of a given engine; the questions of first cost and expense of attendance being of comparatively minor consequence. The quantity of fuel required to produce a stated power depends upon the construction of the engine itself, upon the character of the boiler and its furnace, and lastly upon the skill exercised in firing. In estimating the horse-power of an engine, the old plan of multiplying the number of square inches of piston surface by the pressure in pounds per inch in the boiler, and dividing the product by thirty-three thousand, should be ignored; it having been proved fallacious nearly half a cen tury ago. Instead of the steam pressure in the boiler, the steam pressure in the cylinder when the piston is in motion must be taken as the multiplier of the piston area. De Pambour, many years since, in France, demonstrated that the pressure of steam on the moving piston is frequently only a quarter as much as the boiler pressnre. This diminution of pressure in the cylinder, as compared with that in the steam-generator, is due partly to bends and impediments in the steam passages, and partly to radiation from the cylinder surface, but in the main to the fact that the steam having to follow the piston is not able to exert its full pressure. From this arises the utility of the indicator showing the steam pressure at all portions of the stroke. For judging a steam engine without regard to the kind of boiler used with it, the weight of steam has until very recently fur. nished the most practical test, although priming, &c., always makes the apparent evaporation greater than that which really takes place. For trials made on this system, Dr. Van der Weyde gave the following as the rules imperative to be observed, if anything approaching reliable results are to be obtained by this method. "1st. The water to be measured in tanks, and not by water meters, which are always unreliable. 2nd. No steam to be used from the boiler, during the trial, for other purposes than for the engine to be tested. 3rd. To let the engine perform a constant well-determined amount of labour during the trial. 4th. The amount of water in the boilers at the end of the experiment should be exactly the same as in the beginning. 5th. When the boilers have blown off salt or muddy water, during the trial, this amount should be ascertained. 6th. The experiments should be very carefully and skilfully performed, and often repeated, in order to eliminate incidental inaccuracies, caused by temperature of the air, variation of water-level, &c." will be placed in the coming International Exhibition as a contribution on the part of the Society of Arts, showing the result of recent efforts which have been made to improve art workmanship in this country. The specimens of manufacture sent in in competition for the above rewards and premiums will have affixed to them the name of The objections to the above method, familiar to the designer and of the workmen in each special engineers, may be obviated by a more truly scienbranch of industry involved in the execution of tific one, which consists in recording the units of the work. Every workman will be eligible to re-heat carried off by the exhaust steam. By simply ceive money premiums proportionate to his merits, providing a condensing engine for and specific This proof will be firmly imprinted in the and to the degree in which he may have contri- time with a definite quantity of water as a conmind by drawing lines (forces) at various angles,buted to the successful results of the whole, whilst densing agent, and noting, by means of a therand looking for the perpendiculars of requiremometer, the degrees of heat communicated to it ments; let fall, remember, from the end of the by the condensation of the steam, the quantity of lines representing the forces, on to the position heat carried off by the exhaust may be found by chosen. This finding of the perpendiculars is the a simple calculation. This has very much facilichief difficulty in the II. and III. Cases; once the tated the accurate testing of different rates of exgeneral run of the reasoning has been understood. pansion, &c. The units of heat thus carried off The student may be further helped by a model in the exhaust are of course so much abstracted with rods (Fig. 60), which can be shifted to any from the force employed to drive the piston, and of the three positions. The unshaded (white) the less this quantity of heat, other conditions rods are the forces P and Q, made long to have being equal, the more efficient the engine for a the prolongations. A pin, a, with chain to keep given expenditure of fuel. The mode of applying them at the right angle for Case I.; two short These works may obviously include specimens the test is very simple, it being only necessary black rods bb hang from the top of the parallelo- not only of the taste of the designer, but of the to place one thermometer in the inlet of water to gram. They coincide with P ́and its parallel in skill of the carver, inlayer, metal worker, chaser, the condenser and the other at the outlet of the the first case. Two long black rods CC, extend bronzist, engraver, china painter, die sinker, latter. By noting the difference in the temperafrom the end of the parallelogram and coincide cameo cutter, glass worker, enameller, mosaicist, tures indicated by the two, it remains only to know with Q and its parallel in the first case. They and other art workmen, either separately or in the quantity of water passed through the concan be pinned as the forces. Draw pins and shift any combination arranged. denser per minute, and the results may be readily The society hope that they may receive objects enabling the judges to award the society's gold medal to manufacturers, and the society's silver medal to manufacturers or designers-accompanied, in the latter case, if the circumstances appear to call for it, with money premiums; and to the art workmen money premiums varying from £3 to £20, and to the extent, in the whole, of £500. computed. In testing high pressure or non-con- 2ft. high, showing a tremendous motion towards facula is under the slit) we suddenly see this apdensing engines the same principle is applied, but the eye. There were light clouds, which reflected pearance an interesting bright lozenge of light in a somewhat different manner, the exhaust to me the solar spectrum, and I therefore saw the This I take to be due to bright hydrogen at a steam being turned into water in a tank of known black C line at the same time. The prominence greater pressure than ordinary, and this then is capacity, so that the rise in temperature for a C line (on which changes of wave-length are not the reason of the intensely bright points seen in given time furnishes, as in the previous instance, so well visible as in the F line) was only coinci- ranges of faculæ observed near the limb. the required data of the heat carried from the dent with the absorption-line for a few seconds of engine by the exhaust. SPECTROSCOPIC OBSERVATIONS OF THE SUN.* BY J. NORMAN LOCKYER, F.R.S. lately been enough, and THE weather has noth, dening my available observation time, to enable me to resume work. The crop of new facts is not solarge as it would have been had I been working with a strip of the sun, say fifty miles or a hundred miles wide, instead of one considerably over 1000-indeed, nearer 2000 in width; but in addition to the new facts obtained, I have very largely strengthened my former observations, so that the many hours I have spent in watching phenomena, now perfectly familiar to me, have not been absolutely lost. The negative results which Dr. Frankland and myself have obtained in our laboratory-work in the matter of the yellow bright line near D, in the spectrum of the chromosphere being a hydrogen line, led me to make a special series of observations on that line, with a view of differentiating it, if possible, from the line C. It had been remarked, some time ago, by Prof. Zollner, that the yellow line was often less high in a prominence than the C line; this, however, is no evidence (bearing in mind our results with regard to magnesium). The proofs I have now to lay before the Royal Society are of a different order, and are, I take it, conclusive :1. With a tangential slit I have seen the yellow line bright below the chromosphere, when the C line has been dark; the two lines being in the same field of view. 2. In the case of a bright prominence over a spot on the disc, the C and F lines have been seen bright, while the yellow line has been invisible. 3. In a high-pressure injection of hydrogen, the motion indicated by change of wave-length has been less in the case of the yellow line than in the case of C and F. 4. In a similar quiescent injection the pressure indicated has been less. 5. In one case the C line was seen long and unbroken, while the yellow line was equally long, but broken. The circumstance that this line is so rarely seen dark upon the sun makes me suspect a connection between it and the line at 5015 Angstrom, which is also a bright line, and often is seen bright in the chromosphere, and then higher than the sodium and magnesium lines, when they are visible at the same time; and the question arises, must we not attribute these lines to a substance which exists at a higher temperature than those mixed with it, and to one of very great levity? for its absorption-line remains invisible, as a rule, in spot-spectra. I have been able to make a series of observations on the fine spot which was visible when I commenced them on April 10th, not far from the centre of its path over the disc. At this time, the ot, as I judged by the almost entire absence of indications of general absorption in the penumbral regions, was shallow, and this has happened to many of the spots seen lately. A few hours' observation showed that it was getting deeper apparently, and that the umbra were enlarging and increasing in number, as if a general downsinking were taking place; but clouds came over, and the observations were interrupted. By the next day (April 11) the spot had cer tainly developed, and now there was a magnificently bright prominence, completely over the darkest mass or umbra, the prominence being fed from the penumbra or very close to it, a fact indicated by greater brilliancy than in the bright C and F lines. April 12. The prominence was persistent. April 15. Spot nearing the limb, prominence still persistent over spot. At 11 I saw no prominence of importance on the limb, but about an hour afterwards I was absolutely startled by a prominence not, I think, depending on the spot I have referred to, but certainly near it, more than * Read before the Royal Society, May 19. arc! Ten minutes afterwards the thickness of the I pointed out to the Royal Society, now more 1. Those in which great action is going on, lower vapours being injected; in the majority of cases these are not high, they last only a short time-are throbs, and are often renewed, and are not seen so frequently near the sun's poles as near the equator. They often accompany spots, but are not limited to them. These are the intensely bright prominences of the American photographs. 2. Those which are perfectly tranquil, so far as wave-length evidence goes. They are often high, are persistent, and not very bright. These do not, as a rule, accompany spots. These are the "radiance" and dull prominences shown in the American photographs. I now return to my observations of the spot. On the 16th, the last of the many umbræ was close to the limb, and the most violent action was indicated occasionally. I was working with the Cline, and certainly never saw such rapid changes of wave-length before. The motion was chiefly horizontal, or nearly so, and this was probably the reason why, in spite of the great action, the prominences, three or four of which were shut out, never rose very high. I append some drawings, made, at my request, by an artist, Mr. Holiday, who happened to be with me, and who had never, seen my instrument or the solar spectrum widely dispersed before. I attach great importance to them, as they are the untrained observations of a keen judge of form. The appearances were at times extraordinary and new to me. The hydrogen shot out rapidly, scintillating as it went, and suddenly here and there the bright line, broad and badly defined, would be pierced, as it were, by a line of intensely brilliant light parallel to the length of the spectrum, and at times the whole prominence spectrum was built up of bright lines so arranged, indicating that the prominence itself was built up of single discharges, shot out from the region near the limb with a velocity sometimes amounting to 100 miles a second. After this had gone on for a time, the prominence mounted, and the cyclonic motion became evident; for away from the sun, as shown in my sketch, the separate masses were travelling away from the eye; then gradually a background of less luminous hydrogen was formed moving with various velocities, and on this background the separate "bombs" (I was working with a vertical spectrum) like exquisitely jewelled ear-rings. It soon became evident that the region of the chromosphere just behind that in which the prominence arose, was being driven back with a velocity something like 20 miles a second, the back-rush being so local that, with the small image I am unfortunately compelled to use, both the moving and rigid portions were included in the thickness of the slit. I saw the two absorbing--lines overlap. These observations were of great importance to me; for the rapid action enabled me to put together several phenomena I was perfectly familiar with separately, and see their connected meaning. They may be summarised as follows, and it will be seen that they teach us much concerning the nature of prominences. When the air is perfectly tranquil in the neighbourhood of a large spot, or, indeed, generally in any part of the disc, we see absorption-lines running along the whole length of the spectrum, crossing the Frauenhofer lines, and they vary in depth of shade and breadth according as we have pore, corrugation, or spot under the corresponding part of the slit-a in fact, is a spot. Here and there, where the spectrum is brightest (where a bright point of Proc. Roy. Soc. 1869, p. 354, Mar. 17. pore, The appearance of this lozenge in the spectrr scope, which indicates a diminution of p re ssu round its central portion, is the signal for some, and often all, of the following phenomena :1. A thinning and strange variation in the visibility and thickness of the hydrogen absorption-line under observation. 4. If near the limb, this prominence may extend beyond it, and its motion-form will then become more easy of observation. In such cases the motion is cyclonic in the majority of cases, and generally very rapid, and-another feature of a solar storm-the photospheric vapours are torn up with the intensely bright hydrogen, the number of bright lines visible determining the depth from which the vapeurs are torn, and varying almost directly with the amount of motion indicated. Here, then, we have, I think, the chain that connects the prominences with the brighter points of the facule. These lozenge-shaped appearances, which were observed close to the spot on the 16th, were accompanied by the "throbs " of the eruption, to which I have before referred; while Mr. Holiday was with me-a space of two hours-there were two outbursts, separated by a space of almost rest, and each outburst consisting of a series of discharges, as I have shown. I subsequently witnessed a third outburst. The phenomena observed on all three were the same in kind. On this day I was so anxious to watch the various motion-forms of the hydrogen lines, that I did not use the tangential slit. This I did the next day (the 17th of April) in the same region, when similar eruptions were visible, though the spot was no longer visible. Judge of my surprise and delight, when upon sweeping along the spectrum, I found hundreds of the Frauenhofer lines beautifully bright at the base of the prominence! ! ! The complication of the chromosphere spectrum was greatest in the regions more refrangible than C, from E to long past b, and near F, and high pressure iron vapour was one of the chief causes of the phenomenon. I have before stated to the Royal Society that I have seen the chromosphere full of lines; but the fulness then was as emptiness compared with the observation to which I now refer. A more convincing proof of the theory of the solar constitution, put forward by Dr. Frankland and myself, could scarcely have been furnished. This observation not only endorses all my former work in this direction, but it tends to show the shallowness of the region on which many of the more important solar phenomena take place, as well as its exact locality. The appearance of the F line, with a tangenial slit at the base of the prominence, included two o the lozenge-shaped brilliant spots to which I have before referred; they were more elongated than usual-an effect of pressure, I hold, greater pressure and therefore greater complication of the chromosphere spectrum; the complication is almost impossible of observation on the disc. It is noteworthy that in another prominence, on the same side of the sun, although the action was great, the erupted materials were simple, i.e., only sodium and magnesium, and that a moderate alteration of wave-length in these vapours was obvious. Besides these observations on the 17th, I also availed myself of the pureness of the air to examine telescopically the two spots on the disc, which the spetroscope reported tranquil as to up and down rushes. I saw every cloud-dome in their eighbourhood perfectly, and I saw these domes drawn out, by horizontal currents, doubtless, in the penumbra, while on the floors of the spots, here and there, were similar cloud-masses, the distribution of which varied from time to time, the spectrum of these masses resembling that of their fellows on the general surface of the sun. I have before stated that the region of a spot comprised by the penumbra appears to be shallower in the spots I have observed lately (we are now nearing the maximum period of sun spots); I have further to remark that I have evidence that the chromosphere is also shallower than it was in 1868. I am now making special observations on these two points, as I consider that many important conclusions may be drawn from them. MECHANICAL MOVEMENTS.* (Continued from page 292.) Intermittent rotary motion from MECHANICAL MOVEMENTS. bevel-gears gearing to the horizontal ones, one | bound themselves by charter to deal with accordfast and the other loose on the shaft. Suppose ing to the spirit in which the Exhibition had been the hoop to be held stationary, motion given to conceived, and the object for which the public either vertical bevel-gear will be imparted through money had been asked for and received-that is, 164. Intermitten rotary motion about an the horizontal gears to the other vertical one; in the encouragement of art and industry. It was axis at right angles. Small wheel on left is driver; and the friction rollers on its radial studs work against the faces of oblique grooves or projections across the face of the larger wheel, and impart motion thereto. but if the hoop be permitted it will revolve with the vertical gear put in motion, and the amount of power required to hold it stationary will correspond with that transmitted from the first gear, and a band attached to its periphery will indicate 165. Cylindrical rod arranged between two that power by the weight required to keep it still. rollers, the axes of which are oblique to each other. 173. Robert's contrivance for proving that The rotation of the rollers produces both a longi-friction of a wheel carriage does not increase with tudinal and a rotary motion of the rod. velocity, but only with load. Loaded waggon is 166. Drilling machine. By the large bevel-supported on surface of large wheel, and connected gear, rotary motion is given to vertical drill-shaft, which slides through small bevel-gear but is made to turn with it by a feather and groove, and is depressed by treadle connected with upper lever. 167. A parallel ruler with which lines may be drawn at required distances apart without setting out. Lower edge of upper blade has a graduat ed ivory scale, on which the incidence of the outer edge of the brass arc indicates the width between blades. 168. Describing spiral line on a cylinder. The spur-gear which drives the bevel-gears, and thus gives rotary motion to the cylinder, also gears into the toothed rack, and thereby causes the marking point to traverse from end to end of the cylinder. 169. Cycloidal surfaces, causing pendulum to move in cycloidal curve, rendering oscillations isochronous or equal-timed. with indicator constructed with spiral spring, to therefore invested in such a manner as should render it available, at some future time, for the establishment of permanent exhibitions. That time has now arrived, and the series that commences next year is therefore the direct result of the Exhibition of 1851, and the Commissioners intend to bear the whole cost and responsibility, without either government money or public guarantee. To Permanent exhibitions must of necessity be established on a different basis than those which are temporary, if they are to be successful. The promoters of the Exhibition of 1851 had no statistics by which they could be guided into the right course of action. The many exhibitions that have, however, been held since in this and 174. Rotary motion of shaft from treadle by other countries have afforded proof that there are means of an endless band running from a roller certain limits of time, space, and expense which on the treadle to an eccentric on the shaft. cannot be exceeded without loss and failure. 175. Pair of edge runners or chasers for crush-hold them at any other period than between the ing or grinding. The axles are connected with months of May and September, is practically to vertical shaft, and the wheels or chasers run in an shut out many of the productions of Northern annular pan or trough. Europe, where the ports are closed by the rigours of winter. The expense of the erection of temporary buildings for decennial exhibitions was constantly increasing, and, with other charges, rendered it necessary for those who undertook their promotion to incur a heavy pecuniary liability, which, coupled with the limits as to the time during which the exhibition conld remain open, rendered financial success, at each succeeding exhibition, more difficult of attainment. 176. Tread-wheel horse-power turned by the weight of an animal attempting to walk up one side of its interior; has been used for driving the paddle-wheels of ferry-boats and other purposes by horses. The turnspit dog used also to be employed in such a wheel in ancient times for turning meat while rsasting on a spit. 170. Motion for polishing mirrors, the rubbing of which should be varied as much as practicable. The handle turns the crank to which the long bar and attached rachet-wheel are connected. The mirror is secured rigidly to the ratchet-wheel. The long bar, which is guided by pins in the lower rail, has both a longitudinal and an oscillating movement and the ratchetwheel is caused to rotate intermittently by a click operated by an eccentric on the crank-shaft, and hence the mirror has a dulum, is represented as cutting a lying tree. compound movement. 177. The tread-mill employed in gaols in some countries for exercising criminals condemned to labour, and employed in grinding grain, &c; turned by weight of persons stepping on tread-boards on periphery. This is supposed to be a Chinese in vention, and is still used in China for raising water for irrigation. 171. Modification of mangle-wheel motion. The large wheel is toothed on both faces, and an alternating circular motion is produced by the uniform revolution of the pinion, which passes from one side of the wheel to the other through an opening on the left of the figure. 172. White's dynamometer, for determining the amount of power required to give rotary motion to any piece of mechanism. The two horizontal bevel-gears are arranged in a hoop-shaped frame, which revolves freely on the middle of the horizontal shaft, on which there are two vertical Extracted from a compilation by Mr. H. T. BROWN, Editor of the "American Artisan." 178. Saw for cutting trees by motion of pen (To be continued.) EXHIBITION OF 1871. THE year 1871 will see the first of a series of Generally, the exhibitions outgrew their limits. For the fulfilment of their legitimate purpose, which was to show from time to time the progress made by art and industry, in connection with the staple manufactures of the country in which they were held, necessitated that a large number of objects should be received, required enormous space for their exhibition, though in themselves possessing but little merit as objects of artistic industry. With these facts before them, the Commission ers propose, in the first place to make an International Exhibition a permanent institution of the country, giving to the industrial art the same opportuniy that is afforded to fine art by the annual exhibitions of the Royal Academy. In the second place, they propose to reduce the area over which the exhibition shall spread itself, by reducing the various industries into groups, and taking certain of these each year, bring the entire industry of the country under review every seven or eight years, fine art being a standing division REVIEWS. "The Modern Practical Angler: A Complete London: F. Warne and Co. "Drawing for Carpenters and Joiners, &c., &c." By ELLIS A. DAVIDSON. Cassell, Petter, and Galpin. of the programe. And, in the third place, to number of triangles and hooks, as was formerly strong wind is blowing in' that direction, and as restrict the conditions under which exhibits have the fashion-sometimes no fewer than three to most experienced anglers are of his way of thinkhitherto been received, by making all articles un-five of the former being used on one flight-and ing, there cannot be much doubt that he is dergo a preliminary sifting, through appointed he attributes to them, and to the "crinkling" or correct, especially as this method is found to fail committees of selection, thus excluding all works "kinking" of the line, the loss of about 50 or 60 in practice. The author likewise advises-what that do not possess sufficient artistic merit to per cent. of fish after being struck. Here are his will be considered rank heresy by some-that in warrant their exhibition, and by the further ex- own words:"These [triangles] were not only spinning for pike the fisherman should strike clusion of mere masses of natural products. useless, but distinctly mischievous, both as directly he feels a run. But we have limits to The great aim of the early periodical exhibi- regards the spinning of the bait and the basketing our space, and must conclude by observing that tions established by the Society of Arts was the of the fish when hooked. Upon the bait they the remaining chapters of Mr. Pennell's book, clo er union of art and industry; this was also the acted by impairing its brilliancy and attractive-containing a description of the different varieties object which H.RH. the Prince Consort had so ness, rendering it flabby and inelastic. Upon the of fish, their habits and their haunts, together much at heart in promoting the first Great Ex-fish they operated only as fulcrums, by which he with the method of angling for them, and the hibition. The Commissioners now propose, in was enabled to work out of the hold of such hooks best kinds of tackle to use in endeavouring to these permanent exhibitions, to carry on the work as were already fast. The great size and defective achieve their capture. There are also some exof bringing about a closer alliance between artistic bends of many of the hooks used, contributed cellent lithographs, which really represent the design and usefulness of purpose, by, to use their materially to swell the proportion of losses, as it fish they are intended for, and there is a coloured own words, “stimulating the application of the should be remembered that to strike a No. 20 frontispiece representing the flies the author artists' talents, to give beauty and refinement to hook fairly over the barb, requires at least three considers sufficient for all practical purposes. every description of object of utility." times the force that is required to strike in a No. We may have occasion to refer to this work again, 10; and that this disparity is increased when the but in the mean time we are confident that while hooks are used in triangles. A jack, say, has the fisherman who is a proficient in his art will taken a spinning-bait dressed with a flight of find much to claim his attention, it is a very three or four of these large triangles, and a vade-mecum for all tyros who wish to become sprinkling of single hooks-perhaps 11 or 12 in masters of the "gentle craft." all. The bait probably lies between his jaws, grasped crosswise, and therefore the points of at least six of these hooks will be pressed by the fish's mouth, whilst the bait also to which they are attached is held firmly in his teeth. The whole of this combined resistance must be over- WE bave on three previous occasions drawn come-and that at one stroke, and sharply-attention to the very cheap and good before a single point can be buried above the technical manuals by Mr. Ellis A. Davidson, barb." recently published by Messrs. Cassell, Petter, and Galpin. The present volume is thoroughly worthy of its predecessor on "Building Construction," and should reach a far wider circle. All of us are, or think ourselves more or less carpenters, and the more or less miserable specimens of the art some amateurs occasionally turn out, should serve to remind them of the necessity of their possessing a book like the one before us. If one thing is more certain than another it is that good execution must be preceded by good design, and a carpenter unable to use his pencil labours under terrible disadvantages. "Drawing," as Mr. Davidson most truly says, "is the language of the workshop more eloquent than words, more rapidly understood, and less liable to be misapprehended." The book is so arranged as to combine linear, freehand, and object drawings each of these branches being again divided and subdivided, and thus in linear drawing, foundations, piles, cofferdams, wooden bridges, roofs, staircases, doors, gates, &c., are made subjects of study. Mouldings, borders, whilst under the head of object drawing, a few scrolls, &c., are included in the freehand section; simple rules of perspective and shading are given, in order to enable the student to draw with some degree of correctness from the subject before him. WE E imagine that most of our readers who have any pretensions to be considered fishermen, or who have followed the windings of any of our beautiful streams in search of the pleasure which Angling affords alike to the greatest statesmen as to the meanest kind, will not require to be told that Mr. Pennell is one of our most accomplished anglers, whether in theory or practice. Those who have read his "Book of the Pike" well know the amount of information he Las brought to light concerning the habits and peculiarities of the "pirate of the river"indeed, so carefully and minutely has he described the life-history of this fish, that he is commonly called the "Father of Pike-fishers." We offer no apology, therefore, for plunging at once into the mysteries of the craft, convinced that what Mr. Pennell recommends, however novel, is at all events worth trial; and as the holidays are drawing near, we will see what he has to say towards filling the creels of such of our readers as may betake them to the Tweed, the Blackwater, or the Thames. 44 In the matter of "kinking," Mr. Pennell has inquired into what might be called the science of the subject; and instead of passing his tract through the centre of the weight, in which position the lead could not, of course, prevent the line from turning, he fastens the lead to the side of the line, or, at least, in such a position that nearly the whole weight is exerted against the twisting of the line. He recommends that the lead should be varnished with powdered dark-green sealing-wax, mixed with spirits of wine to the consistency of thin treacle. With the lead fixed in this manner one really good swivel will be found sufficient, although a double one avoids any hitch that might arise through the single swivel being rusty. Speaking of trollinglines, the author is decidedly opposed to hair, when used by itself (when a line 80 yards long would cost 25s. or 30s.), or mixed with silk; but recommends the use of what is known as 8-plait dressed silk, of a pale green tint. For bottom-fishing and fly-fishing lines gut is is not scraped, and made small artificially, and to be preferred-the fine, round, natural gut, that consequently weaker. For reel-lines for fly-fishing, Mr. Pennell, till The author commences his manual by saying dressed silk; but he has recently tried a line within the past twelvemonths, has used the that pike and trout, like other mundane creatures, made of spun cotton, which, while much cheaper are better educated, or at all events sharper, than than the dressed silk, is equally strong and more their progenitors of the time of Izask Walton or durable. It is "cable-laid"-i.e., the "ropes" of Dame Juliana Berners, who wrote the "Boke of which the cable is made are twisted the reverse St. Alban's," published about 1486, wherein the of the strands, and the twisting of the "cable" rod is recommended to be of at least some 14ft. is the opposite of the "ropes." Mr. Pennell long; the "staffe" or butt, measuring a fadoom (fathom) and a-half," of the thickness speaks highly of these lines, and says they of an "arm-grete," or about as thick as a man's "answer perfectly, both for fly-fishing and ordinary bottom fishing." arm, the joints being bound with long "hopis of yren" (iron hoops). But whether fish are more intelligent, or are simply more timid, from their inability to find in the United Kingdom a mile of water that is not haunted by those tantalising flies that have wrought the doom of so many of used in the manufacture of rods, and the proMr. Pennell next describes the various woods their comrades, Mr. Pennell is decidedly and cesses they undergo before they appear as the emphatically of opinion that the man who fishes perfect implement. He prefers as a general rule, * finest "will be able to show the heaviest creel rods with ash butts, and niddles and tops made at the close of a day's sport. of greenhart (? greenheart), and, what will sur"Chapter I. lays down the theory of what a hook prise most readers, says, that the difference in should be, describes the various forms of hooks weight between rods of solid wood and those hitherto used, and after pointing out their made of bamboo, is so trifling, as scarcely to be humerous deficiencies, explains the advantages of worthy of consideration:-"I weighed a 12ft. Dir. Pennell's pattern, which has all the good solid ash and greenhart trolling-rod, against one qualities of the "sneck" and "sproat-bend," of stout East India bamboo, and the weights without their drawbacks. It much resembles the were:-solid rod 1lb. 54oz., hollow rod 1lb. 4oz.; sneck," but with a difference in bend, as well difference, 1oz." The knots used in fastening as in the barb and point, and is certainly much lines and hooks are elaborately described, and tronger, because the strain is distributed, and being illustrated, are made plain to the merest Boes not fall on one part. The author has, also, tyro. devised a new form of the rather-important It would take a whole chapter to thoroughly lip-hook," on which depends the proper posi- examine Mr. Pennell's theory of flies and fly. ion of the bait and flight. By leaving the shank fishing; and we must be content to state that, the hook unpolished, and altering the position instead of expatiating on the allurements and of the loops so that the line lies close to the hook, beauties of the "thousand and one" flies to be he has succeeded in obtaining the requisite ease seen in tackle-shops, he is convinced that six u shifting, and fixity when required, combined typical ones are all that is necessary for the purwith durability and neatness. poses of the angler, no matter what water he is In the matter of spinning tackle Mr. Pennell fishing-three being devoted to salmon and grilse, peaks with no uncertain voice. He unhesi- and three to trout, grayling, &e. Mr. Penuell is atingly condems the employment of such a opposed to fishing up-stream, except when a "The Second Course of Orthographic Projection Mr. Binns' method of teaching mechanical drawing is now practised in the various art schools of the United Kingdom, and we have little doubt that this record of its publication will be gladly |