notch, a, the pin is disengaged from the gab in at the end it lifts the rack by its own movement,, dication of pleasure till the song was finished, the eccentric-rod. 5. A screw-clamp. On turning the handle the screw thrusts upward against the holder, which, operating as a lever, holds down the piece of wood or other material placed under it on the other side of its fulcrum. 6. Scroll-gears for obtaining a gradually increasing speed. 7. A variety of what is known as the "mangle wheel." In this one the speed varies in every part of a revolution, the groove b, d, in which the pinion-shaft is guided, as well as the series of teeth, being eccentric to the axis of the wheel. 8. Another kind of mangle-wheel, with its pinion. With this, as well as with that in the preceding figure, although the pinion continues to revolve in one direction, the mangle-wheel will make almost an entire revolution in one direction and the same in an opposite direction; but the revolution of the wheel in one direction will be slower than that in the other, owing to the greater radius of the outer circle of teeth. 9. Another mangle-wheel. In this the speed is equal in both directions of motion, only one circle of teeth being provided on the wheel. With all of these mangle-wheels the pinion-shaft is guided and the pinion kept in gear by a groove in the wheel. The said shaft is made with a universal joint, which allows a portion of it to have the vibratory motion necessary to keep the pinion in gear. 10. A mode of driving a pair of feed-rolls, the opposite surfaces of which require to move in the same direction. The two wheels are precisely similar, and both gear into the endless screw which is arranged between them. The teeth of one wheel only are visible, those of the other being on the back or side which is concealed from and follows on the other side. 14. Another form of mangle-rack. The THE EAR-ITS USES AND ABUSES. when it uniformly returned to the dovecot." These Toujours gai, toujours gai, them on a far back occasion how a pet canary of mine, since defunct, was very partial to remarkable for containing in its walls the glands The passage to the drum of the ear is chiefly my clarionet, seeming to derive comfort from a furnishing the wax or cerumen, the use of which plaintive air, and eyed me from his perch, but at may be to entangle such small foreign bodies as once sought the bottom of his cage if I played a would go in, or the too adventuresome fly. This loud, quick measure. His demise took place one much is certain: I have over and over again, after day at dinner time, to the inexpressible grief of removing a hard plug, the accumulation it may be of years, found ants, flies, &c., in the body of one of my little ones, whose sobs refused comfort, it; and the wax must have a bitter taste, for no deriving a post satisfaction from the decent in- leech will cross it, nor will it adhere to the skin terment of the bird within sight of the garden until it is perfectly well cleaned of every portion window. "The faculty of imitating sounds posof ear wax. The colour varies from pale straw, as sessed by certain birds proves that the hearing darkness of mahogany and the hardness of old in the infant, and of a honey consistence, to the must be exceedingly delicate, and though we sus-india-rubber. I have often taken an hour for its pend our belief of the great musical talents which removal with the result of restoring hearing. And some birds are said to have derived from educa- here let me make a digression on the common and tion, we find many well attested instances of a indiscriminate use of the syringe. If there is delicate ear in species by no means remarkable pain in the ear it should not be thought of; great for vocal execution." Madame Piozzi gives an injury as well as intolerable agony might result. account of a tame pigeon, which answered by Should the ear passage be impacted the speculum gesticulation to every note of a harpsichord. As is of no use, and a cautious removal of the plug 12. What is called a "mangle-rack." A con- often as she began to play, the pigeon hurried to is all the more necessary, for it may become tinuous rotation of the pinion will give a recipro- the concert with every indication of rapturous moulded to the drum, and even inflame it. I cating motion to the square frame. The pinion- delight. A false note produced in the bird evi- have seen an old person faint from the violent inshaft must be free to rise and fall, to pass round the dent tokens of displeasure, and if frequently rejection of a stream of water into the ear, and guides at the ends of the rack. This motion may peated, it lost all temper, and tore her hands. "A violent cough or vomiting may be equally unbe modified as follows:-If the square frame be no less remarkable instance of the effect of music pleasant. One portion of the ear passage is so fixed, and the pinion be fixed upon a shaft made on a pigeon is related by Lockman in his reflec- intolerant of touch that a probe moved over it with a universal joint, the end of the shaft witions on operas, prefixed to his musical drama of will cause the sensation of nausea; why, I bedescribe a line similar to that shown in the Rosalinda.' Being in the house of a Cheshire lieve anatomists are ignorant of, although comdrawing around the rack. gentleman whose daughter was a fine performer pelled to accept the fact they cannot explain. on a harpsichord, he observed a pigeon, which The tube of the ear in most persons is not whenever the young lady played the song of straight, and it becomes necessary to stretch the Speri Si,' in Handel's opera of Admetus,' would auricle backwards and upwards to see the memdescend from an adjacent dovecot to the room brane; some, on the contrary, have the passage window where she sat, and listen with every in-so large that the membrane of the drum is seen view. 11. The pinion, B rotates about a fixed axis and gives an irregular vibratory motion to the arm carrying the wheel, A. 13. A modification of 12. In this the pinion revolves, but does not rise and fall as in the former figure. The portion of the frame carrying the rack is jointed to the main portion of the frame by rods, so that when the pinion arrives THE EAR-ITS USES AND ABUSES. without difficulty. The direction of the meatus, cious enough in all conscience, has his external however, as long as there are people who like seems to be for the facility of, catching sounds, ear passage expanded from behind into a circular such devices they will be paraded. It requires a addressed as they usually are to the face. In aperture, and his ungainly appropriations are nice sense of touch to be able to hit the passage animals, where hearing is necessary for their thus favoured. To strengthen the assertion of with a proper catheter, the bubble heard being safety, things are otherwise ordered; take the the hare's deficient hearing in advance of her, the your test of success. Attached to the drum memhare for example, Fig. 9, and also in the pole-story is told of one pursued by greyhounds along brane is part of one of the chain of ear bones, a cat, Fig. 10. Our ear passage is not of uniforma turnpike road; a woman was approaching im- truly wonderful structure, ever on the move; no calibre, but wider or funnel-shaped below, so mediately in front of her, she knelt down and the noise of clockwork here, balanced to a nicety, that in using the speculum it is only possible to hare ran fairly into her apron, which was stretched and retained in that balance by ligaments or binds see a portion at a time. The bony passage is in- out to receive her. This circumstance clearly to the bone walls adjacent. Every vibration is complete in the young, and in their case we get a proves that poor puss was much more occupied conveyed by this swinging chain of ossicles, or better view of the parts; what we see may be with dangers from behind, and heedle-s of those little bones, to the fenestrum, or window of the briefly described, and Fig 1 will convey some before her; she preferred, however, to yield her- vestibule, the fourth bone, or the third, according idea thereof. The first thing that attracts you if self to her who is ever the refuge of the perse- to some, closing that opening with a stopper you are sharp-eyed is a spot of white and a line of cuted and oppressed, and we may hope for the shaped like a stirrup. The hammer bone, Figs. white where the handle of the malleus or hammer credit of her sex she did forego the temptation 2, 3, and 4, acts on its neighbour the anvil, and bone is attached as if sewn to the membrane; you for once of roast hare and currant jelly. You this in turn on the stirrup, which is supposed to next perceive that the light shines off one part know, of course, that in the martial instrument be a compound bone. You can easily imagine that is higher than the rest, and if you look closely of percussion, provision is made for bracing up that if one of these bones was to be dislocated or and in a good light having a suitable ear for ob- or tightening the drum-head. Well, the ear is thrown out of its joint, what mischief would enservation, you may possibly be gratified to see provided with a tensor tympani muscle or sue; the outer membrane of the drum is often one part of it vibrate; to do this, however, you stretcher of the drum, and as the hole in the in- destroyed, and impaired hearing results. That must possess a Brunton's speculum, which magni-strument is supposed to be an air hole, so our the ear bones are not an absolute essential of the fies the object, and a first-rate light. In colour cavity of the drum is supplied with one. Some hearing organ is evidenced by their absence in the drum membrane is a mother of pearl white, contend that there is no analogy, and that the air fishes; and in man the foramen ovale may be at like thin gold-beater's skin. It readily inflames, sent through the Eustachian tube from the throat times seen through the disrupted membrana tymthen assumes a pink colour, at all times sensitive is to counterbalance the atmosphere and prevent pani, and yet the relic of hearing remains, of to the touch, the slightest pressure causing pain concavity of the membrane. This tube, called course useless if the liquor Cotunnii (called after and sickness. I believe it was Sir A. Cooper who after one Eustachius, opens into the throat be- Cotunnus, an anatoinist) is evacuated. A broken conceived the idea of puncturing the membrane, hind the soft palate, and performs a most im- external membrane may be replaced by an artian operation that would require the nicest touch, portant function in hearing, for its closure is fol- ficial drum of Yearsley's, a neat little disc of indiaand, after all, of questionable utility. Although lowed by deafness; its calibre is small, although rubber, wired, but if the inner membrane is gone, surgeons might be numbered by the thousand, the opening in the bell-shaped extremity of the the "sanc um sanctorum" of the ear is invaded, few have ever taken the trouble to see the ear-throat is large and wide; if the lining coat of and all is lost. Those of you who have seen boys drum, and I have seen some who considered it is inflamed, easy closure results, or it may be lifting a stone with a leather sucker, get some themselves very intelligent observers, direct the rendered more or less impervious by mucus filling idea as to the action of the artificial drum; it is tube of the speculum to the wall of the meatus, and it up. To remedy this defect a Eustachian ca- the putting of a new patch on an old garment, or describe what was out of sight. Fine hairs line the theter or tube is devised to pass by the floor of a patching operation like what we see on an old passage, a cheveaux de frise in the face of an in- the nose into the bell muscle, and is connected drum worn out in the vigorous service of a Punch trader. The adaptation of means to end is remark-with an air reservoir exhausted and closed by a and Judy proprietor. able, and to be traced everywhere in nature; for in- stop cock; the connection being established, a jet stance, the ear passage in the owl is high up, just of air is forced into the cavity of the drum. In where he wants it-the hare's is directed backwards two instances death has followed the use of this with a long canal and highly movable ear, so elaborate machine, and its employment is perthat puss may be a match for her pursuers; the fectly unnecessary, for if you inflate the cheeks, reverse obtains in the polecat, who" follows his having stopped the nostrils with a finger and nose," and so deaf are they to what goes on at their thumb, you may fill the cavity if the canal is perback, that a story is told of a farmer who in trying vious, and the bursting of a bubble of air is audito shoot one missed fire five or six times, and not ble to the stethoscope of a listener. Catheters a move was apparent on the part of the polecat and probes are sold by the boxful to go into this until he was turned out of ie. The fox, preda- passage, but they are too large to gain admission; The vestibule into which the stapes is fitted communicates with the semi-circular canals and cochlea. See Fig. 1. The auditory nerve comes through the internal passage from the brain, and is in that opening said to be in close communication with the facial nerve, a fact of the highest importance in diseases of the ear. The vestibule I might liken to the hall of a house, the oval window being the door; it has no great vestibular proportions, being about the 8th of an inch in diameter. Numerous openings for nerves and vessels occupy the walls, and the apertures of the semi-circular canals are there noticed; another opening leads into the cochlea, which has been aptly compared to a winding staircase or a whelk shell. Figs. 5 and 6. Two of the semi-circular canals join at their extremities. The upper diameter is about the 20th of an inch; the lower part has a dilatation, or ampulla, on it. One of the canals is horizontal, the other perpendicular, and as this mode of arrangement is widely observed in nature, it is supposed that they regulate the direction of the sound. This winding staircase makes two turns and a half, and is about an inch and a half long; its central stem, called axis, or modiolus, terminates above in a funnel-like expansion. These several cavities have linings, and contain fluid which appears to be useful in the transmission of vibrations, and another fluid or layer of peri lymph is said to exist between the membrane and the bone proper. There is a curious powder found in the ear called otoconia, a compound of carbonate and phosphate of lime, crystalline. The diameter of some of these mysterious grains, the use of which we are unacquainted with, is of an inch; they are 3000 supposed to be analogous to the otoliths or ear bones of fish, and the presence of this otoconia in the lower types of organisation leads to the conclusion that they are for hearing purposes. This vestibule is a chamber in which the auditory nerve is spread, and receives its impressions. It may seem marvellous, but M. Savart states that sounds are still audible which result from the succession of 24,000 impulses (Carpenter), and this probably is not the extreme limit of acuteness. 1 These vibrations are determined, either by a num. ber of apertures passing a sounding pipe in a given time, or the number of teeth caught by a spring in the same period. (To be continued.) CHAPTERS ON CURIOUS CATERPILLARS.-APRIL. BY J. R. S. CLIFFORD. some of its habits are very curious. Indeed, much attention has been directed to these in late years, since the ravages committed by them on the apple and pear trees in some Midland counties have been serious. The parents of the numerous broods of these ravenous rovers, which seem to feed on almost any tree in wood or orchard, come forth from the chrysalis state in the dreary months of November and December; the male moths, with semi-transparent, dull brown wings, sitting quietly on palings through the day; the females, which are nearly wingless, running along the trunks and branches of trees, where they deposit their eggs, each one usually laying 200. The small caterpillars which emerge, begin by gnawing the just opening buds, when great numbers are destroyed by birds, which visit the buds in search of them, and frequently destroy buds on which, apparently, no caterpillars were feeding a weakness which the gardener is inclined to punish severely. As the foliage becomes full the caterpillars of the winter moth prepare for themselves habitations, constructed by drawing two or three leaves together, in which the little tenant dwells with tolerable safety, thrusting his head a little beyond it to feed, but rarely exposing himself entirely to view. When disinclined to eat, he reposes with his head on one side and partly curled round; and when a tree or shrub haunted by them is tapped smartly, out tumbles a host, some descending to the ground, others swinging by silken threads. In appearance these caterpillars vary very greatly, the general colour being various shades of green, or even brown approaching to blackish, a central stripe down the back, which marks the position of the alimentary canal-or long stomach, shall we call it ?-being seen in all, and other fainter stripes each side, more or less distinct. When of full size, they descend to the ground, and enter the earth to complete their change, and the sudden disappearance of them towards the end of May from this cause is striking; where a few days before the insect-hunter, in beating the bushes, shook forth thousands, only a straggler or two appears, but the dismantled bushes do" a tale unfold" of what has been done by the individuals now reposing quietly as chrysalides. a moth which frequently enters houses, and is as variable as the caterpillar which produces it. This latter also, like its brethren, lives through the winter, but seems to feed on without cessation, living in the roots of plants, or concealed in the stem. When brought to view it rolls up into a compact ring. The colour is most frequently some tint of brown, though sometimes the ground is yellowish-green; a number of narrow stripes run from head to head to tail, interspersed with black markings. When it has ceased to eat, it scoops out a slight cell in the earth, and appears as a moth in June and July. The caterpillar and chrysalis shown in our : The figure are those of the Brimstone Butterfly Gorepteryx Rhamni) the former begins to the curiously sculptured eggs are deposited at the appear in April on the species of buckthorn; beginning of the month on the tips of the young leaves. Until they get to be of some size, the caterpillars lie along the mid-rib of a leaf, when at rest, and thus escape notice. In favourable seasons arrive at their full size in twenty-five days from they grow with great rapidity. I have had them the time of emergence from the egg and in a fortnight afterwards the brilliant butterfly comes forth from the chrysalis. The caterpillar is of a dull green, curiously shagreened over with minute points, with a paler line along each side. with yellow. Common as is the Meadow Brown chrysalis, rather singular in shape, is green tinted Butterfly (Satyrus janira), its caterpillar has, as yet, been little noticed; it must be got by stooping. May. In the day it is usually at rest near the bottom of some stem of grass, and when touched falls off in a tight ring, remaining doubled up for a good while. This is one of the caterpillars which has been called rolling-pin shaped; the surface is rough, and also studded with scattered hairs, and on the last segment are two little points; the colour of the body is apple-green, with a darker stripe. The chrysalis is attached by silk WHEN vegetation, generally, has fairly by the collector, because it is most partial to down and examining the grass fields in April and yielded to the influences of Spring, and almost before many of the trees have been able to display their leaf glories in full perfection, a numerous and indefatigable host of insect adversaries is sure to be engaged in attacking bud, leaf, flower, or even the wood of the tree itself. Sometimes the attack is carried on in the broad daylight, at other times it is insidious; the marauder lurking during the day, and sallying forth at night, leaving, however, manifest traces of the execution done by his jaws. The first general brood of the caterpillars, which produce our butterflies and moths, emerge from the egg, in great rart, during April, though a few are delayed till May. Others, which ceased to feed in the early chills of Autumn, and were too cautious to be tempted from their winter retreats by the transient fine weather of March, crawl forth in the milder month of April, and, regardless of its showers, regale themselves on the fresh spring leaves. Regardless of its showers," did I say? Not altogether so; for many caterpillars succumb to them, and will be "found drowned" after a heavy rain fall chiefly those which have not long emerged from the egg. In the gales, too, which continue some seasons to prevail through part of April, others are blown from their food-plants into roads or other positions, where they are either readily seized by birds, or die from starvation, through being unable to regain the plant or tree which yields their wonted So that gardeners and agriculturists have reason to rejoice that the ravages of caterpillars, at their greatest, are nothing to what they might be, were all circumstances favourable to their nutriment and growth. Nor must we forget the singular circumstance, that in addition to external enemies, every species of caterpillar has, as we believe, an internal enemy, in the shape of some parasite, which, at a certain point in the career of a large number of each kind, deposits its eggs upon the skin, and the grubs produced therefrom devour, slowly or gradually, the luckless individuals attacked. diet. Surely the most abundant of the April caterpillars, is that which produces the Winter Moth (Chimatobia brumata), and common as it is, A rather odd caterpillar, not frequently found gardens and their vicinity, which he is apt to be negligetn in hunting, is that of the Swallowtailed Moth (Ouraptery sambucata), this moth floats slowly about the hedgerows on July evenings, and is easily taken. The caterpillar, which is getting of some size in April, is of a varying brown hue, and looks exceedingly like a bit of twig which has been snapped off, and the resemblance is kept up by little humps along the The elder is a back, almost resembling buds. in gardens and orchards, extending itself usually tree on which it often feeds, as also on fruit trees at full length along a branch when not eating. In June it suspends itself in a sort of hammock, made of bits of leaves and silk intermixed, in which it turns to a palish chrysalis, spotted with black. Amongst the night-feeding caterpillars, the individuals belonging to the genus Tryphaena, are to be detected at night, and are occasionally looked for with a lantern by those interested in the doings of insects. Most of them have lived through the winter, and in April they ascend the trees at night and nibble the buds and young leaves, retiring to the ground at early morning, aud hiding amongst the short herbage. That of the very handsome moth, called the Broad Bordered Yellow Underwing (T. fimbria), is fond of making midnight excursions on birches and sallows, where it may be rather readily found, being noticeable by its namerous markings scattered over the clay-brown velvety skin; the head is very small, shining, and mottled. So also acts the caterpillar of the smaller and more abundant Lesser Yellow Underwing (T. arbona), but as it rolls, when touched, into a compact ring, it often falls to the ground and is missed. The colour and markings resemble those of its relative, and at certain times it aprears to feed also on chickweed in the daytime. When of adult size, it becomes a chrysalis on the surface of the ground, and the moth appears about a month after. The Lesser Broad Bordered (Tjanthina), another of the family, in its caterpillar state, prefers to feed on garden plants of a variety of kinds, feeding in the daytime on the roots, and emerging from the ground at night to nibble the leaves. The most abundant of the genus is the well-known Yellow Underwing (T. prowwba), to the grass. aquatic places, is that which includes the Wain- and deep black, the body dingy white, with black dots and bristles, and a horny plate behind the head. Unlike the preceding, when full grown, de caterpillars quit the stem, and change to chrysalides on the ground. Many a young collector of insects has carried home with triumph the handsome caterpillar of the Drinker Moth (Odonestis potatoriz), which feeds on grass in the early morning throughout required, that is, by means of the rack wheel on THE WAVES LECTURE was delivered at the Midland a heavy body acquired in falling through a depth equal to half the virtual depth of disturbance. The periodic tidal wave, the effect of waves upon the coast, the concentration of the energy of the wave upon being compressed into a channel, when its height became considerably increased, and the breaking up of the wave by an abrupt diminution in the depth of the water, were treated by the lecturer. In connection with the behaviour their refraction and reflection were noticed, and the lecturer, announced in conclusion, that his next discourse would be an explanation of the action of waves as regarded the stability and repulsion of ships. the spring, but not unfrequently during the day, A Instituts, Birmingham, on the 21st ult, by of the waves upon rolling in towards the shoru, it climbs up some neighbouring twig to bask in the sunshine, leading persons to the natural, yet erroneous conclusion that it eats the plant on which it is found. This caterpillar is coated with hair, even to the feet, and is thus well enabled to defy the cold of winter. The colours are very varied, the back being blue-grey, mottled with black, with orange spots and streaks along the sides. The cocoon is formed of silk, and is of a leathery texture, and attached to a blade or two of grass. The name "drinker" was given to the species because the caterpillars have a habit of occasionally sipping the dew drops, and if kept in confinement, get on all the better if the food given them is damp, contrary to what is the case with the majority. sea. BLANE'S IMPROVED MACHINE FOR neering relating to such works. Their motion MORTISING TIMBER. THIS HIS improved machine for mortising timber, patented by G. N. Blane, of Glasgow, consists of an upright framing or standar to which the moving parts are attached. The moving parts consists of a foot lever attached by a pin joint to the lower part of the framing or standard, and from the back part of such lever FIG A The motion of such waves was a subject which possessed a great deal of scientific and practical interest, inasmuch as it was against these waves that a defence had to be provided in the shape of breakwaters and sea walls, and a knowledge of their motion and the force they exerted was of great importance in civil engiaffected in an important degree the motion of vessels, the stability and resistance of ships, and the power required for their repulsion. Therefore, a knowledge of the motion and the force exerted by waves was of the greatest importance in naval architecture and ship-building. The present lecture would embrace an explanation of the nature of the motion taking place in the waves of the sea, and the force they exerted. The THE MANCHESTER INSTITUTION OF ENGINEERS. Mr. W. J. Macquorn Rankine, Professor of FIG.2 FENCE FENCE TABLE a connecting rod passes up and is connected to another lever at the upper part of the framing or standard. This lever is carried on a centre or centres fixed in the framing or standard, and its front end is connected by links to the bar which earries the mortising tool or tools. Below the mortising tool or tools an adjustable table for carrying the timber to be mortised is situated. Fig. 1 is a front view, and Fig. 2 a side view of the machine. A, the upright framing or stan dard; A1, the foot lever; A2, the upper lever which is made forked, motion being communicated from the foot lever Al to the upper lever A2 by a back rod; B, spindle for the mortising tool; C, tool in spindle; D, handle for reversing the spindle and tool; E, spring catch to keep the spindle in the proper place when it is rereversed; F, gauge to move to any depth of wood and keep the wood from lifting when the spindle with the tool is rising; G, pinching pins to fix the gauge to ang height; HL, screws for shifting the table in or out from I te J; K, wheel to lift the table up or down to any height H Anon lecturer then popularly illustrated by means of The second part of the proceedings opens with the presidential address of Mr Hulse, who is termed the father of the institution. Mr. Hulse offers some very practical remarks upon the subject of light railways. (The same volume contains no less than five papers upon the Irwell floods, with suggestions for their remedy. Two of these papers are by Mr. J. Fletcher, the others being by Mr. G. Lowry, Mr. J. Corbett, and Mr. Trapp, respectively. The proceedings for 1869 are not yet printed, but an important paper on the patent laws, read by Mr. Theodore Aston, at a meeting of the institution held on the 4th of January paper is peculiarly opportune at this time, as the last, has been published. The reading of this subject of the patent laws is likely to be discussed in the House during the present session. In this paper, and also in the discussion which followed its reading, and in which several gentlemen well qualified to deal with the question, took part, will be found some sound suggestions upon the whole snbject. We have only to add that the institution is represented in London by Mr. W Lloyd Wise, who is the honorary secretary, and who has promised to furnish us with copies of the papers read at the meetings of the institution, and which, if they correspond with those that have preceded them, will prove very interesting to our readers. THE TRUE VELOCIPEDE. R. THOMAS CLARKE, of Wilmslow, D cheshire, has published his paper read in September last, before the International Conference held in the Crystal Palace on the "Scien drums or pulleys on nave; & handles to pulleys; | in diameter, its bed twenty-one and a half feet tific principles which should guide in the foot-crank. NEW YORK. seat in the middle; though the single wheel WE give a series of engravings illustrating In Figs. 1 and 2 a are the saddles; b middle and prevents the earth from falling upon the workmen. After a section of the tunnel sixteen inches long has been erected within the hood, the pump is operated, which causes the rams to slide out from the shield and push with great force against the front edge of the tunnel, driving the shield forward into the soil. As the shield advances, the earth presses through between the shelves, and falls down upon the bottom of the shield, whence it is removed in barrows and cars. As soon as the shield has been advanced sixteen inches its movement is stopped and a new section of the masonry tunnel is erected within the hood. The shield is then again pushed forward, and so on. By means of this machine tunnels of all kinds and sizes may be quickly constructed under the streets, without disturbing the travel of vehicles over the surface. The shield may be readily moved around circles or on grades. It was designed by Mr. A. E. Beach, of the Scientific American. It In the pneumatic system the cars are propelled wholly by atmospheric pressure. One of our engravings gives a view of the interior monster blowing engine used by the Pneumatic Transit Company for this purpose. Its shell (A) is 21 ft. high, 18ft. long, and 13 ft. broad. contains two pairs of wings or blades (B), which roll together in such a manner as to exhaust and compress an immense quantity of air at every revolution. The machine is made on Root's patent, and is by far the largest of its kind. It has capacity for delivering about two hundred thousand cubic feet of air per minute. ON THE PHENOMENA OF COMBUSTION. this subject in the Lecture Room of the Society of Arts, John- |