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notch, «, the pin is disengaged from tho gab in the eccentric-rod. 2 ami 3. Modifications of 1.

4. Another modification of 1

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 orother 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 re-volution, 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 direotion; 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 eqnal 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 tho 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 view.

11. The pinion, B rotates about a fixed axis and gives an irregular vibratory motion to the arm carrying the wheel, A.

12. What is called a " mangle-rack." A continuous rotation of the pinion will give a reciprocating motion to the square frame. The pinionsbaftmustbefrcetorise andfall, to pass round the guides at the ends of the rack. This motion may be modified as follows :—If the square frame be fixed, and tho pinion be fixed upon a shaft made with a universal joint, the end of the shaft wi describe a line similar to that shown in the drawing around the rack.

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

MECHANICAL .MOVEMENTS.

at the end it lifts the rack by its own movement, and follows on the other side.

14. Another form of mangle-rack. Tho lantern-pinien revolves continously in one direction, and gives reciprocating motion to the square frame, which is guided by rollers or grooves. The pinion has only teeth in less than half of its circumference, so that while it engages one side of the rack, the toothless half is directed against the other. The large tooth at the commencement of each rack is made to insure the teeth of the pinion being properly in gear.

15. A mode of obtaining two different speeds on the same shaft from one driving-wheel.

THE EAR—ITS USES AN'D ABUSES.

By Dr. Usshee.

(Continued from page G.)

SOME of my readers may remember that I told them on a far back occasion how a pet canary of mine, since defunct, was very partial to my clarionet, seeming to derive comfort from a plaintive air, and eyed me from his perch, but at once sought the bottom of his cage if I played a loud, quick measure. His demise took place one day at dinner time, to the inexpressible grief of one of my little ones, whose sobs refused comfort, deriving a post satisfaction from the decent interment of the bird within sight of tho garden window. "The faculty of imitating sounds possessed by certain birds proves that the hoaring must be exceedingly delicate, and though we suspend our belief of the great musical talents which some birds are said to have derived from education, we find many well attested instances of a delicate ear in species by no means remarkable for vocal execution." Madame Piozzi gives an account of a tame pigeon, which answered by gesticulation to every note of a harpsichord. As often as she began to play, the pigeon hurried to the concert with every indication of rapturous delight. A false note produced in tho bird evident tokens of displeasure, and if frequently re peated, it lost all temper, and tore her hands. "A no less remarkable instance of the effect of music on a pigeon is relatod by Lockman in his reflections on operas, prefixed to his musical drama of 'Rosalinda.' Being in the house of a Cheshire gentleman whose daughter was a fine performer on a harpsichord, he observed a pigeon, which whenever the young lady played the song of 'Speri Si,' in Handel's opera of' Admetus,' would descend from an adjacent dovecot to the room window where she sat, and listen with every in

dication of pleasure till the song was finished, when ituniformly returned to the dovecot." These quotations are full of interact. You all know the story of the watchful geeso in the Roman Capitol. Throughout creation yon will come across people as diverse in their hearing as in their tastes; some cannot for the life of them turn a tunc, and others will twist it and torture your ears by such wretched discords that escape is impossible and endurance a virtue—others can't abide it; of them I would say, "Shun that man or woman who dislikes to hear music or the voice of a child!" And what is more musical than the unrestrained laugh of a coterie of little ones? It is a happy power—the laugh of the maiden is contagious, and if she is ringing the silver bell of her voice it is a peean of victory, and reminds me of a dear old song:

Toujours gal, toujour* pit,
Always meet a smile h.JMvny,
Always meet a sniilu holf-woj,
And iollow my example.

Tho passage to the drum of the ear is chiefly remarkable for containing in its walls the glands furnishing the wax or cerumen, the use of which may be to entangle such small foreign bodies aa would go in, or the too adventuresome fly. This much is certain : I have over and over again, after removing a hard plug, the accumulation it may be of years, found ants, flies, to., in the body of it ; and the wax must have a bitter taste, for no leech will cross it, nor will it adhere to the skin until it is perfectly well cleaned of every portion of ear wax. The colour varies from pale straw, as in the infant, and of a honey consistence, to the darkness of mahogany and the hardness of old india-rubber. I have often taken an hour for its removal with the result of restoring hearing. And here let me make a digression on the common and indiscriminate use of the syringe. If there is pain in the ear it should not be thought of; great injury as well as intolerable agony might result. Should the car passage be impacted the speculum is of no use, and a cautious removal of the plug is all the more necessary, for it may become moulded to the drum, und even inflame it. I have seen an old person faint from tho violent injection of a stream of water into the ear, and violent cough or vomiting may be equally unpleasant. One portion of the ear passage is so intolerant of touch that a probe moved over it will cause the sensation of nausea; why, I believe anatomists are ignorant of, although compelled to accept the fact they cannot explain. The tube of the ear in most persons is not straight, and it becomes necessary to stretch the auricle backwards and upwards to see- tho membrane ; some, on the contrary, have- the passage so large that the membrane of the dram is seen

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•without difficulty. The direction of the meatus seems to be for the facility of, catching sounds, addressed as they usually are to the face. In animals, where hearing is necessary lor their safety, things are otherwise ordered; take the hare for example, Fig. 9, and also in the polecat, Fig. 10. Our ear passage is not of uniform calibre, but wider or funnel-shaped below, so that in nsing the speculum it is only possible to gee a portion at a time. The bony passage is incomplete in the young, and in their ca«e we get a better -view of the parts; what we see may be briefly described, and Fig 1 will convey some idea, thereof. The first thing that attracts yon if you are sharp-eyed is a spot of white and a line of white where the handle of the malleus or hammer bone is attached as if sewn to the membrane ; you next perceive that the light shines off one part that is higher than tho rest, and if you look closely and in a good light having a suitable ear for observation, jou may possibly be gratified to see one part of it vibrate; to do this, however, you must possess a Bruuton's speculum, which magnifies the object, and a first-rate light. In colour the drum membrane is a mother of pearl white, like thin gold-beater's skin. It readily inflames, then assumes a pink colour, at all times sensitive to the touch, the slightest pressure causing pain and gickness. I believe it was Sir A. Cooper who conceived the idea of puncturing the membrane, an operation that would require the nicest touch, and, after all, of questionable utility. Although surgeons might be numbered by the thousand, few have ever taken the troublo to see the eardrum, and I have seen some who considered themselves very intelligent observers, direct the tube of the speculum to the wall of the meatus, and describe what was out of sight. Fine hairs line the passage, a chcreaux de frite in the face of an intruder. The adaptation of means to end is remarkabIc,andtobe traced every where in nature; for instance, the ear passage in the owl is high up, just where hewants it—the hare's is directed backwards with a long canal and highly movable ear, so that puss may be a match for her pursuers j the reverse obtains in the polecat, who "follows hi* nose," and so deaf are they to what goes on at their back, that a story is told of a farmer who in trying to shoot one missed fire five or six times, and not a move was apparent on the part of the polecat until he was turned out of i e. The fox, preda

THE EAK—ITS USES AND ABUSES.

cious enough in all conscience, has his external ear passage expanded from behind into a circular aperture, and his ungainly appropriations are thus favoured. To strengthen the assertion of the hare's deficient hearing in advance of her, the story is told of one pursued by greyhounds along a turnpike road ; a woman was approaching immediately in front of her, she knelt down and the hare ran fairly into her apron, which was stretched out to receive her. This circumstance clearly proves that poor puss was much more occupitd with dangers from behind, and heedle s of those before her; she preferred, however, to yield herself to her who is ever the refuge of the persecuted and oppressed, and we may hope for the credit of her sex the did forego the temptation for once of roast hare and currant jelly. You know, of course, that in the martial instrument of percussion, provision is made for bracing up or tightening the drum-head. Well, the ear is provided with a tensor tympani muscle or stretcher of the drum, aud as the hole in the instrument is supposed to be an air hole, so our cavity of the drum is supplied with one. Some contend that there is no analogy, and that tho air sent through the Eustachian tube from the throat is to counterbalance tho atmosphere and prevent concavity of the membrane. This tube, called after one Eustachius, opens into the throat behind the soft palate, and performs a most important function in hearing, for its closure is followed by deafness; its calibre is sin.ill. although the opening in the bell-shaped extremity of the throat is large and wide j if the lining coot of it is inflamed, easy closure results, or it may be rendered more or less impervious by mucus filling it up. To remedy this defect a Eustachian catheter or tube is devised to pass by the floor of the nose into the bell muscle, and is connected with an air reservoir exhausted and closed by a stop cock ; the connection being established, a jot of air is forced into the cavity of the drum. In two instances death has followed the use of this elaborate machine, and its employment is perfectly unnecessary, for if you inflate the cheeks, having stopped the nostrils with a finger and thumb, you may fill the cavity if the cannl is pervious, and the bursting of a bubble of air is audible to the stethoscope of a listener. Catheters and probes are sold by the boxful to go into this passage, but tbey ure too largo to gain admission;

however, as long as there are people who like such devices they will be paraded. It requires a nice sense of touch to be able to hit the passage with a proper catheter, the bubble heard being your test of suocess. Attached to the drum m:-mbrane is part of one of the chuin of cur bones, a truly wonderful structure, ever on the move; no naise of clockwoik here, balanced to a nicety, and retained in that balance by ligamonts or binds to the bone walls adjacent. Every vibration is conveyed by this swinging chain of ossicles, or little bones, to tho fenestras), or window of the vestibule, the fourth bone, or the third, according to some, closing that opening with a stopper shaped like a stirrup. The hammer bone, Figs. 2, 3, and 4, acts on its neighbour the anvil, and this in turn on the stirrup, which is supposed to be a compound bone. You can easily imagine that if one of these bones was to be dislocated or thrown out of its joint, what mischief would ensue ; the outer membrane of the drum is often destroyed, and impaired hearing results. That the ear bones are not an absolute essential of the hearing organ is evidenced by their absence in fishes; and in man the foramen ovale may be at times seen through the disrupted membrana tympani, and yet the relic of hearing remains, of course useless if the liquor Cotunnii (called alter Cotunnus, an anatomist) is evacuated. A broken external membrane may be replaced by an artificialdrumof Ycatsley's, aneat little disc of indiarubber, wired, but if the inner membrane is gone, the "sane.urn sanctorum" of the ear is invaded, and all is lust. Those of you who have seen boys lit ting a stone with a leather sucker, get Borne idea as to the action of the artificial drum ; it is the putting of a new patch on an old garment, or a patching operation like what we see on an old drum worn out in the vigorous service of a Punch and Judy proprietor.

The vestibule into which the stapes is fitted communicates with the semi-circular canals aud coehlea. See Fig. 1. Tho auditory nerve comes thruugh the internal passage from the brain, and in in that opening said to be in close communication with the facial nerve, a fact of the highest importance in di-eoses of the ear. Tho 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 :n diameter. Numerous openings for nerves and vessels occupy the walls, and the apertures of the 6enii-circular canals are there noticed j another opening leads into the cochlea, which has been aptly compared to a winding staircase or a whelk shell. Figs. 6 and 6. Two of the semi-circular canals join at their extremities. The npper 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 staireaso makes two turns and a half, and is about an inch and a half long; its central stem, called oxis, 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, und 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 the^e mysterious grains, the use of which we are unac1

quaintcd 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 bearing 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. These \ilirations are determined, either by a number 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 CATER-
PILLARS.—APRIL.

By J. R. S. Clipfoed.

WHEN vegetation, generally, has fairly 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 Bure 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 trace3 of the execution done by bis jaws. The first genera' brood of the caterpillars, which produce onr butterflies and ninths, 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 cautions 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, Tegale themselves on the fresh spring leaves. "Regardless of its showers," did I ssy? Not altogether so; for many caterpillars succumb to them, and will bo "found drowned " after a henvy 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 tbey are either readilyseized by birds, or die from starvation, through heing unable to regain the plant or tree which yiolds their wonted diet. So that gardeners and agriculturists have reason to rejoice that the ravages of caterpillars, at tbeir greatest, are nothing to what they might be, were all circumstances favourable to their nutriment and growth. Nor must we forget the singularcircumsiance, that in addition toexternal 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 largo number of each kind, deposits its eggs upon the skin, and the grubs produced therefrom devour, slowly or gradually, the luckless individuals attacked.

Surely the most abundant of the April caterpillars, is that which produces the Winter Moth (.Clumatvbia brumata), and common aB it is,

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 s me 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 bead 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 rather odd caterpillar, not frequently found by the collector, because it is most partial to gardens and their vicinity, which be is apt to be uegligetn in hunting, is that of the Swallowtailed Moth {Ourapteryx tambucata), this moth floats slowly about the hedgerows on July evenings, and in 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 back, almost resembling buds. The elder is a tree on which it often feeds, as also on fruit trees in gardens and orchards, extending itself usually 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 Trypheena, 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, and hiding amongst the short herbage. That of the very handsome moth, called the Broad Bordered Yellow Underwing (T. jimbtia), is fond of making midnight excursions on birches and sallows, where it may be rather readily found, being noticeable by its mmerous 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 appears to feed also on chickweed in the daytime. When of adult size, it becomes a chrysalis o» the surface of the ground, and the moth appears about a month after. The Lesser Broad BonJered (T.janthina), another of the family, in its caterpillar state, prefers to feed on garden plants of a variety of kinds, feeding in the daytimeon the roots, and emerging from the ground at night to nibble the leaves. The most ahuudnnt of the genua i» the well-known Yellow Underwing {T.promrba),

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 soma tint of brown, though sometimes the ground is yellowish-green ; a number of narrow stripes run from head to head to tail, iuterspersed 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

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figure are those of the Brimstone Butterfly Gorcpteryx Rhamni): the former bpgins to appear in April on the species of buckthorn; the curiously sculptured eggs are depn.nted at the 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 they .grow with great rapidity. I have had them arrive at their full size in twenty-five days from the time of emergence from the egg; and in a fortnight afterwards the brilliant butterfly cornea forth from thechrysalis. The caterpillar is of a dull green, curiously shagreened over with minute points, with a paler line along each Bide. The chrysalis, rather singular in shape, is green tinted with j cllow. Common as is the Meadow Brown Butterfly (Stityrwjanira), its caterpillar haB, as yet, been little noticed ; it must be got by stooping down and examining the grass fields in April ana May. In the day it is usually at rest near the bottom of Borne stem of grass, and when touched falls off in a tight ring, remaining doubled op for a good while. This is one of tbo 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 Wttle points; the colour of the body is apple-green, with a darker stripe. The chrysalis is attached by silk to the grass.

An interesting family of moths, which haunt aqnatie places, is that which includes the Wainscot Moths, which flit to and fro, as soon as evening sets hi, some appearing in July, others in Angnst and September. The habits of the caterpillars are in many respects singular, most of them living through the winter, and feeding; up iu the Bpring. Some of these may be readily found in April, in marshy ground, and on tk« banks of streams and ditches. The Snioky Wainscot (Levcanlm impnra) is a London insect, occurring about the Thames, and common throughout the three kingdoms. The caterpillar, yellowish grey, with paler lines, feeds on different grasses, and may be swept from them with a net. So also does the caterpillar of the Common Wainsoot {Levmnia pallerti), which is full grown in April, and is greyish-brown in colour, dotted along the back with black, and marked with delicate longitudinal lines. In the reed mace, in many places, the larger caterpillar of the Bull-rash Moth (Nonofrin typhi?.) may be found, thoagh as yet small, since it is not full grown till July. This caterpillar is long, and has a smooth head, and a strong plate in the second segment, which enables it to move with facility within the stem of the plant, where it subsists on the pith. By a remarkable instinct, when about to change, it cuts a circular hole in the Bide of the stem, comiag close to, bnt not through the surface, and leaving a thin film through which the future moth easily pushes its way. Another lover of fens and marshes is known, as the Fen Wainscot ( €alamia phragm i I. id is), once abundant near Greenwich, and still plentiful in Cambridgeshire. Tfte caterpillars live in the stems of the common reed, where t!;ey may bo found aear the tip in April. These are rather mtiggot-Hke, and when removed from their reoreats, «t*w! about restlessly. The- asad is small

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, i.«« 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 (Odonestu potatorit), which

feeSs on grass in the early morning throughout

the spring, but not unfrequently during the day,

U climbs up some neighbouring twig to bask in

the sunshine, leading persons to the natural, yet

erroneooj 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 oolours are very

varied, the back being blue-grey, mottled with

black with orange spots and streaks along the

aides.' 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

oecasionally 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.

required, that is, by means of the lack wheel on its (EU) axis which acts on the rack, shown in the drawing; L, strong bolt to fix the table when at the proper height.

BLADE'S IMPROVED MACHINE FOB MORTISING; TIMBER.

THIS improved machine for mortising timber, patented by G. N. Blane, of Glasgow, consists of an upright framing or standard ! to whieh the moving parts are attached. The moving parts consists of a foot lever attached by B pin joint to the lower part of the framing or standard, and from the back part of such lever

THE WAVES.

ALEOTURB was delivered at the Midland Institute, Birmingham, <>u the jl&t ult.bv Mr. W. J. Macquorn Rankine, Professor of Engineering aad Mechanic in the University of Glasgow, on " Waves." The lecturer said he was not going to lecture upon those classes of waves, the existance of whioh was inferred by means of scientific reasoning, such as light waves, nor upon that class of waves whose existence, though a matter of demonstration, was not obvious to the senses, like sound waves; but the waves upon which he was about to speak were those commonly understood as liquid waves, like the waves of the sea. 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 ir. the shape of breakwaters and sea walls, and a knowledge of their motion and tte force they exerted was of great importance in civil engineering relating to such works. Their motion affected 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 tba greatest importance in naval "architecture and ship-building. The present lecture would embrace an explanation of the nature of the motion taking plaee in the waves of the sea, and the foroe they exerted. The

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 of the waves upon rolling in towards the shore, their refraction and reflection were noticed, and the lecturer, announced in conclusion, that his next discourse would be an explanation of the action of wares as regarded the stability and repulsion of ships.

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« connecting rod passes up and is ■connected to another lever at the upper part of the framing or standard. This lever is carried -en a centre or centres fixed in the framing or standard, and its front end is connected by links to the bar which earries the mortisWg tool or toeia. 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 standard; At, the foot lever; A2, the upper lever which is made forked, motion being communicated from the foot lever A* to the upper lever As by a back red; 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 re- reversed; F, :gauge to mow to any depth of wood and keep the wood frein lifting when the spindle with the tool is rising; G, pinching pins to fix the gauge to any height; H, screws for shifting the table in or out froml te J ; K, wheel to Itft the table up «■ down to «*f height

lecturer then popularly illustrated by means of
diagrams the way in which the waves were origin-
ated, by some foreign body pushing the particles
of water in a forward direction, when they became
beaped up, which direction they communicated to
the particles immediately beyond them ; but, in
returning to their original level, they lost their
forward motion, The action of the wind upon
the water formed a long ridge, which, however,
was not a continuous advancing motion, but au
alternate rising and falling of the particles. In
the most simple kind of wave motion, the
particles of water advanced and retired, each
individual particle describing a circle in about a
central position, by a series of crests and troughs.
This was the motion of the long Atlantic swell,
and such waves had been known to [travel 2000
miles with but little diminution in size. The
modification which this wave motion underwent
according to the depth of water, and the pro-
duction of stationary waves, were illustrated. The
speed with whieh the crest of the wave moved
forward the lactarer explained to be the same as

THE MANCHESTER INSTITUTION OF
ENGINEERS.

OME three years since Mr. William W Hulse, M. Inst, C.E., and| several other, eminent engineers of Manchester, perceiving the want of a good local institution for the advancement of engineering science, formed themselves into a society under the above title. The early proceedings of this institution have lately been printed, and are now before us. The names of those gentlemen who have taken an active part in the working of the institution indicate the value of its proceedings to engineers generally. A combined knowledge of the thoughts and ideas of practical men engaged in the various departments of mechanical science, helps greatly to qualify an engineer for general practice. It is to this end that such institutions are formed, and they are worthy of every support, whilst they are devoted to the mutual exchange and diffusion of the knowledge acquired by members during tho pursuit of their respective branches^ of engineering. Turning to the " Transactions," wo find the first part comprises the address of the president for 1867, Mr. George Peel of Manchester. After referring to numerous matters of interest, the President expresses a hope that it will not be long before a professorship of engineering is endowed in Owens College, and a professor appointed for instructing the pupils in that branch of scientific knowledge, which is one of the most important—in a practical point of view—to which they can apply themselves. The establish ment of such a professorship would undoubtedly prove of considerable interestto all connected with engineering. The next meeting reported was occupied by a paper on dead stroke power hammers, by Mr. James Fletcher, Jun., and another on life boats and their appliances, by Mr. J. Corbett. Both subjects were fully discussed at a subsequent meeting. The remaining papers in, the volume under notice are respectively on friction breaks and couplings, by Mr. T. A. Weston, and on patent fuel, by Mr. G. W. Ommaney,

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 s ime 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 those 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 Januarylast, has been published. The reading of this paper is peculiarly opportune at this time, as the 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 subject. 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.

DR. THOMAS CLARKE, of Wilmslow, Cheshire, has published his paper read in September last, before the International Conference held in the Crystal Palace on the "Scien

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tifio principles which should guide in the construction of velocipedes." Starting on the assumption that, with a properly made velocipede, and on level roads, an economy of time and power is gained, Dr. Clarke adverts to the delusion entertained by many mechanics, that power may be created by mechanical aids. Our subscribers are tolerably familiar with some of the contrivances produced by such persons— machines with any number of toothed wheels and pinions, each additional complication entailing a loss of power rather than a gain. In the construction of. bicycles and other locomachines, the principles to be chiefly borne in rr.md and acted on are safety, simplicity, and /isapness. The medium must be Bought between lightness and strength, the loss by friction must be reduced to the lowest point, and the power be applied to the wheel as directly as possible. As abo there are two sets of independent muscles in the human body—one below and one above the waist—it is essential that, in a properly constructed machine, the two eets shall be able to act either independently or cnmbined. These and other objects appear to have been kept in view by Dr. Clark« in the construction of the machines invented by him, drawings of which are given with his book, and which we reproduce. ."Fig. 1 and 2 are a plan-view and a sidei'rawing of a tricycle of a superior description to carry four—two men sit over the front wheels, a third over the back, and the fourth in a cushioned seat in the middle; though the eingle wheel may be put in front, if preferred, and the middle seat be put looking backwards. Again, a perfect change of muscular power is provided for, as the front men work a power and half levers, and the bind one foot cranks—as in Machine No. 3 and 4. It can be steered from behind, from the middle seat, or by the front wheels, as the axle is boxed in the middle. Foot rests are provided as a fulcrum for the feet, and a back rest as one for the back, enabling the whole power to be Spent upon the levers. It can be dragged both from the front and hind wheels. One mau on the hind seat has propelled himself and the machine enrrying anoiher person with the greatest ease. If the middle seat is removed and the mid-fork is strengthened so as to do away with an axle, it is, Dr. Clarke believes, the very lightest and easiest-worked carriage possible that could be constructed to carry three persons.

In Figs. 1 and 2 a are [he saddles; J middle seat, cushioned; с inner foot-crank for inside lever; d foot crank for hind seat; e anterior forks; / mid-fork fastened to anterior fork ; g small hand-levers to turn the hind-wheel, for middle man; A the cords for do. ; ¿ movable back-rests; к «xle, boxed in the middle; I foot rest for front men ; m the drag; n horizontal projections for toes to press the drag on the wheel ; p hand levers (a power and a half); s luggage shelf. In Figs. 3 and 4 a are the front wheels; b hind wheol; с middle fork; d platform on which workers stand; e bent axles to support platform ; f small supplementary wheel to prevent, tilting forward ¡ g slot or sliding joint te .«mgtheu or shorten carriage; h cone

TUF TKUF VELOCIPEDE.

drums or pulleys on nave; к handles to pulleys; I treadle for foot in down stroke; m seat for men resting. Figs. 5 and 6 are plan and side views of a new bicycle. In this machine, according to the inventor, all complications are weeded out as far as possible. It can'be taken to pieces in a few minutes, and packed in a box a yard sqnare. The hind-fork is curved, and may be made springy to distribute the shocks of the roadway, as well as lessen their force. The mud-protector fits on a square at the top of the front-fork, the foot-rest with the foot-drag above that, and the hind-fork over all, protected by a thick india-rubber washer and kept in its place by a screw—the mud-guard and the foot-rest turning with the wheel. In level countries the foot-rest will not be needed at at all; and no one should use a foot-rest, i.e., go down hill, until he has the machine under perfect control. The ordinary leg-rest is a dangerous feature in the common bicycle. On the new plan there is quite sufficient play for guiding the wheel round any curve in the road, a is the front fork ; b guard; с hind fork; d saddle and spring ; f curved bar supporting foot-rest and drag ; g foot-rest; h projection to press the drag; i drag. Fig. 7 shows a semicircular metal clip to fix underneath the foot, the better to grasp the foot-crank.

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in diameter, its bed twenty-one and a half feet below the surface of Broadway. The mouth of the tunnel opens directly into a largo underground apartment, one hundred and twenty feet in length, fitted up in good style, for tho purposes of a waiting and reception station. This apartment is lighted from the pavement, and occupies the entire space under the Warren-street sidewalk. The tunnel starts from the east end of the reception-room, and extends on a curve to the centre of Broadway, thence in a straight line down to a point a little beyond Murray-street, where the shield, or tunnelling machine, now rests. We present two views of the novel mechanism by which the tunnel is bored, one of which shows the workmen engaged in driving the machine ahead; the other a sectional diagram, showing the details of construction. The shield consists of a large cylinder, open at both ends, witt» shelves arranged within the front end to receive the earth and prevent it from falling too rapidly into the shield ; at the rear of the latter, placed around its periphery, is a series of power/nl hydraulic rams, eighteen in number, all connected with a single water-pump. From the rear of the shield, and passing entirely around it, extends a hoop or band of sheet steel, two feet wide, and one-eighih of an inch thiok, termed the hood. The brick tunnel is erected within this hood, which at all times covers the end of the masonry, 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 cut 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 boen advanced sixteen inches its movement is stopped and a new section of the masonry tnnnel 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 iho streets, without disturbing the travel of vehicles over the snrface. The shield may be readily moved around circles or on grades. It wae designed by Mr. A. E. Beach, of the Scientific American.

In the pnenmatic system the cars are propelled wholly by atmospherio 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 214ft. high, 18ft. long, and 13ft. broad. It coutains 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.

The tunnel commences at the corner of Broadway and Warren-street. The portal of the tunnel, as shown in our engraving, is a massive ornamental structure, of circular form, nine feet

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