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and 8ft. wiie. The total quantity of stone in the bridge is 1,400,000 cubic feet.

Ere it was opened for traffic it had to undergo severe tests to ensure stability and permanence. The first and principal experiment consisted in passdns; two locomotive engines through the tube, and resting them at intervals in the centre of the sections. Another trial was a train of 28 waggons and two locomotives, with 280 tons of coal, drawn into all four tubes.. The deflections caused by these loads were ascertained to be exactly three-fourths of an inch over the immense mass and area of iron.

With the aid of Tab'e I. and the rule, "the tensive strength of a uniform body is directly proportional to its transverse section," we are almost able to determine the tenacity of all materials with which engineers have to deal.

All problems connected with the tensive strength of bodies are reduced to two, or,speaking more concisely, to one, for one is the mere converse opewtkwi to the other. They are :—

1. Reqnire4 tke tensive s'rength, or the eonrtant load, a Wy will safely bear when the dimensions of the transverse area are given t

2. Required the dimensions of the tnuiverse area of a body when the tensive strength of the same material is known per square inoh of sectional area?

The rule for—

1. it—Multiply the strength of an loch har (as in the table) of the body required by the transverse area of square and rectangular bars, or by the square of the diameter* of round bun, and the product will be the ultimate cohesive strength.

Examples based on this rule :—

I. What is the cohesive power of a bar of cast steel2<5in. broad and |in. thick?

Area of transverse area = 2'5 X | = 2-5 X 0-625 = 1-5625.

1 sq. in. bar of cast steel has a tenacity = 19-9 tons.

1-5G sq. in. „ „ „ „ „ =?

= 31044. ___

VJ-a X 1'56 tons Es 31-044 tons = total cohesive Btrength.

II. What is the cohesive power of a round bar of cast steel 2"5in. in diameter.

(2-5)' = 6-25 sq. in. I ciro. sq. in. bar of cast steel has a tenacity = 15m7 tons. 6'25 circ. sq. in. „ ,, „ „ =?

(157 x 625) tons = 98-125tons = [total cohesive strength.

We could have found the total cohesive strength without making use of col. 3 in the table, as follows :—

The area of a circle "whose diameter is equal to (diameter)' 2-5'

2-5in. is X ludophine zz jr r=

4 4

625 X 3141: = 4 898 «q. in. 1 sq. in. bar of

4 cast steel has a tenacity = 19-9 tons 4-808 sq. in. „ „ „ — f

'(191) X 4-898) tons = 9Ttons nearly ~

That this 2nd answer is not quite the same as the first is merely because ia our calculation the decimal fractions have not been sufficiently extended.

III. Required the cohesive power of a bar of Swedish iron of a tranverse section, and dimensions as shown in fig. The upper part of the figure is a trapezoid, and the lower portion is a rectangle ; the sum therefore of these t wo reas gives us the whole transverse section. «

Area of a trapezoid r: add together t e*wo parallel aides, multiply their sum by their breadth or height, and half the product is the 2-25 x 4

area — 22 — 6875 sq. in.

o

Area of rectangle = product of two adjoining side ~l'5x3r45 sq. in.

1 s q. in. bar of Swedish iron has a tenacity

97 tons

11375 sq. in —?

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3'oin. and whose inner diam d ~ 3 in. D* 3-5»

AroA of outer circle ~ — «■ = 314 TM

4 4

9'55 sq. in.

d> 9

„ „ inner ,, = — sr = — 314 = 4 4

706 sq. in.

Area or space contained between them = 2'49 sq. in.

1 sq. in. bar of brass tube has a tenacity = 27 tons.

2tKijip. in. „ „ ,, ,. „ =?

"Total tensive strength «= (2 0(> x 27) = 5562 tons, say 5 tons.

By aid of the above examples the student will find no difficulty in ascertaining the tenacity of any material having a given sectional area, or conversely in finding the dimensions of a piece of material to bear a certain load, so that we may now proceed to

THE TENACITY OP OBTAINS AND HOPES.

Metals when drawn into wire become stronger in respect to tensive strain, (see Table I.), owiog to the wire-drawing process, causing the particles to arrange themselves in continuous fibres. Numerous experiments show that iron wire up to one inch diameter attains a strength of about 30 per cent, greater than that of iron bar; so that while the strength of wrought iron wire may be taken at 8 tons per sq. in., that of iron wire may be taken at 11 tons per sq. in. nearly.

Chains are now so well and so accurately made, and their

soundness and / \ FIG

qualityso readily ascertained by means of the testing machine, that they are much used in crane work on ships, &c, instead of ropes, especially ior outdoor work; but as there are many circumstances in which it may be requisite to UBe ropes, it willbeproper to sbow the strength of both.

Tho strength of a chain is determined by ascertaining the diameters—all are equal to each other—of the metal constituting the links; thus the chain which has a diameter of an inch at A is called an inoh chain, and so on.

Within certain limits the strengths of chains may be estimated in proportion to the squares of the iron's diameter of which they are made ; but it is obvious that when they are made Very large or very small, neither the quality nor the workmanship can be so well relied upon. Iron of large diameter is less fibrous and more crystalline in the fracture, and the welding is more perfect in links of intermediate size. Mr. Glynn for this reason recommends that chains above an inch in diameter should not be employed for crane work, as he prefers chains of smaller dimensions, say £, }, or J of an inch, and reducing the strain upon the chain by increasing the number of the parts that bear it, by means of blocks and pulleyB.

Chains for crane work, are commonly made with

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short links of an oval form, the links being no longer than is necessary to permit the smith to use his tools I for soundly welding the f iron. Chain cables for ships,' or for raising sunken ships \ are mado with the links somewhat longer, and a stud (see Fig. a) or stay is inserted in the link across its least diameter, to support the sides and prevent their collapse under heavy strains.tb us giving great additional strength to the chains. The lattoraro nowadays more or lees done away with, and are replaced by a method patented by Austin in the year 1837, which consists in fastening empty gutta percha vessels or balloons to the ship's sides, and filling these by means of an air-pump with air.

Since studded chains used for cables are stronger than short linked chains without studs, it is not prudent to subject both kinds to tho same proof, when the tenacity of the chains is tested.

The proportions existing between short linked chains to a studded chain is as 7 is to 9, or a simple chain able to sustain a "proof weight" equal to 14 tons—being the proof strain of one inoh chains—will when studded be able to carry 18 tons, which is the Navv proof for iron cables. Both kinds may be safely worked to half the strain to which they have been proved.

The tenacity of chains is generally tried at a mean temperature, the strain being steady, and tho vibration caused by the Wows of the hammer, given in order to detect imperfect welding of a link, is by no means equivalent to the live load— i.e., one that is put on suddenly—it will have to sustain, when exposed, perhaps to a temperature below the freezing point, affecting the strength of iron, as it does that of all crystalline bodies.

The following ore the two practical rules for calculating the diameter, or working load of an iron chain, for computing the tenacity of chains, being calculated at a lower rate than they are generally stated, as it is best to be on the safe side, when we consider what great damages often result from the breaking of a chain, and what is still more carefully to be guarded against, serious injury to life and limb, is inflicted.

1. Extract the Bquare root of 8 times the safe load, and the result will give the diameter in eighths of an inch, or in symbols, if d = diam. in eighths of an inch, W = safe load in tons, theti d = V'TW; or

2. Multiply the weight (tons) to be carried by 30 ; the product will be the square of the i'i im. of the chains reckoned in sixteenths of an inch.

Where long chains required to lift heavy loads are used, it is best to work out the diam. after the first rule, as it gives a little larger diameter to the chaih.

Example: Required the diam. of a simple chain to bear a safe load of 14 tons. a (by rule I.)

d = ./ 814~— «/ lT2~= 10.J of an in.= 14. in. b (by rule II.) -2

A «= V 3014 = V iiii = 20 — of an in. = li ia. 16

N.B.—To find the diamatcr of a chain-cable

5 with studs we have the proposition: — : d. =

4 9 : 7, or diameter=09in., from which the diameter would only require to be:

For tho converse operation namely to find the weight which a chain of given diameter will carry we have :—

1. The quotient of the square of the diameter given in eighths of an inch, divided by 8 gives

the safe load in tons, or symbolically — = W.

2

2. Divide the the square of tho diameter (reckoned in 16ths) by 30, tho quotient will bo the number of tons carried.

Example: What safe load will a chain (simple) bear having a diameter = Jin. a (by rule I.)

6' 36

— = — = 4.} toss: say 4 tons.
8 8

5 (by rule II.)

12' 141 4

— = . = 4— tons: sav 4 toSs.

30 30 0

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The tenacity of ropes depends, as a rule, on the number of threads they are composed of, and ate only employed in those cases where the greatest flexibility is required, and the weight of chains would have been inconvénient.

Ropes are now mostly made by machinery, as hi this process every yarn is made to bear its part of the strain exerted on the whole. There is the considerable difference in the weight and strength of ropes made by hand, and those made by the register, for practice, shows that although the girths—i.e., the circumference—and number of yarns is the same in both, large ropes made by the old method weigh about 7\ per cent, more than those made by the register, and are not even as strong. The strength of ropes also depends very much on the quality of hemp, while the durability of the rope, and, consequently, its trustworthiness in use, are greatly affected by the quality of tar, some of which contains an acid destructive to the hemp, so that it niny be rendered unsafe in 3 years time.

Mons. Du Hamel says that it is a decided fact » r experience that white cordage in continued service is ooc-third more durable than tarred; netoudly it retains its force much longer while kept in store; thirdly it resists the ordinary inj unes of the weather \ longer.

The following experiments were made by the same at Rachfort on cordage 3 French inches eircumferences made of the b st Riga hemp.

MECHANICAL MOVEMENTS.»

{Continued from page 103.)

A /» REPRESENTS a pantograph for copy-
T:Ö» ing, enlarging, and reducing plans, &c.
One arm is attached to and turns on the fixed
pointC. В is an ivory tracing point, and A the
pencil. Arranged as shown, if we trace the lines
of a plan with the point, B, the pencil will repro-
duce it double the size. By shifting the slide
attached to the fixed point, C, and the slide carry-
ing the pencil along their respective arms, the
proportion to which the plan is traced will be
varied.

47. A mode of releasing a sounding-weight.
When the piece projecting from the bottom of the
rod strikes the bottom of the sea, it is forced up-
wards relatively to the rod, and withdraws the
catch from under the weight, which drops off and
allows the rod to be lifted without it.

48. Union coupling. A isa pipe with a small
flange abutting against the pipe, C, with a screwed
end; B a nut which holds them together.

49. Ball-and-socket joint, arrangedfor tnbing.
60. Anti-friction bearing. Instead of a shaft

revolving in an ordinary bearing, it is sometimes
supported on the circumference of wheels. The
friction is thus reduced to the least amount.

51. Releasing-hook, used in pile-driving ma-
chines. When the weight, W, is sufficiently raised,
the upper ends of the hook, A, by which it is
suspended, are pressed inwards by the sides of the
slot, B, in the top of the frame ; the weight is thus
suddenly released, and falls with accumulating
force on to the pile-head.

62. A and B are two rollers which require to be equally moved to and fro in the slot, C. This is accomplished by moving the piece, D, with oblique slotted arms, up and down.

53. Centrifugal check-hooks, for preventing accidents in case of the breakage of machinery which raises and lowers workmen, ores, etc., in

mines. A is to frame-work fixed to the sides of the mine, and having fixed studs, L, attached. The drum on which the rope is wound is provided with a flange, B, to which the check-hooks are attached. If the drum acquires a dangerously rapid motion, the hooks fly out by centrif ogal force, and one or other or all ot them catch hold of the studs, D, and arrest the drumandstop the descent of whatever is attached to the rope. The drum ought besides this to have a spring applied to it, otherwise the jerk arising from the sudden stoppage of the rope might produce worse effects than its rapid motion. .

54. A sprocket-wheel to drive or to be driven by a chain. .

M. A flanged pulley to drive or be driven by a flat belt.

56. A plain pulley for a flat belt.
67. Aconcave-groovedpuUeyforaroundband.

58. A smooth-surface V-grooved pulley for a round band.

59. A V-grooved pulley having its groove notched to increase the adhesion of the bend.

60. A differential movement. The screw, C, works in a nut secured to the hub of the wheel, E, the nut being free to turn in a bearing in the shorter standard, but prevented by the bearing from, any lateral motion. The screw-shaft u secured in the wheel D. The driving-shaft, A carries two pinions, F, and B. If these pinions were of such size as to turn the two wheels, D, and E, with an equal velocity, the screw would remain at rest ; but the said wheels being driven at anequal velocities, the screw travels according to the difference of velocity.

* Extracted from a compilation by Mr. Б, J. Brown, Editor of the American Artisan.

THE GREAT AUK.

By Professor James Orton, In The

"American Naturalist."

THE recent addition of a specimen of this rare bird to the Smithsonian Museum is an event worthy of record. There are now three specimens in the United States; the one just mentioned, another in the Academy of Natural Sciences, Philadelphia, and a third in the Giraui cabinet in Vassar College. The last is the most perfect specimen, and certainly possesses the greatest historical value, as it is the one from which Audubon made his drawing and deMiption. It was caught on the bank* of Newfoundland.

The Great Auk or G are-fowl, fortnnntelj tor itself, did not live long enough to receive more than one scientific name—Alms impenni*. It was about the size of two goose, with a large head, a curved, grooved, and laterally flattened bill: wings rudimental, adapted to swimming only, approaching is this respect the penguins of the pressure is augmented and equalised by means of the bridle E, as above described.

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In the modification of this invention, illustrated in Fig 2, the toothed segments F and G are dis

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southern hemisphere. The toes are fully webbed, the hind one wanting ; the plumage is black, excepting the under parts, the tips of the wings, and an oval spot in front of each eye, which are white. It was an arctic bird, dwelling in the Faroe Islands, Iceland, Greenland, and Newf onndland. "Degraded as it were from the feathered rank (said Nuttall), and almost numbered with the amphibious monsters of the deep, the auk seems eonJemoed to dwell alone in those desolate and forsaken regions of the earth." But it was an on rivalled diver, and swam with great velocity. One chased by Mr. Bullock among the Northern Isles left a six-oared boat far behind. It was undoubtedly a match for the Oxfords. It was finally shot, However, and is now in the British Museum. "It is observed by seamen," wrote Bnffon a hundred years ago, "that it is never seen out of snnedings, so that its appearance serves as an infallible direction to the land." It fed on fishes and marine plants, and laid either in the clefts of the rocks or in deep burrows a solitary egg, five inches long, with curious markings, resembling Chinese characters. The only noise it was known to utter was a gurgling sound. Once very abundant on both shores of the North Atlantic, it is now believed to be entirely extinct, none having been seen or heard of alive since 1844, when two were taken near Iceland.

The death of a species is a more remarkable event than the end of an imperial dynasty. In the words of Darwin, " no fact in the long history of the world is so startling as the wide and repeated extermination of its inhabitants." What an epoch will that moment be when the bet man shall give up the ghost! The upheaval or subsidence of strata, the encroachments of other anímala, and climatal revolutions—by which of these great causes of extinction now slowly but incessantly at work in the organic world, the Great Auk departed this life, we cannot say. Wo know of no changes on our northern coast «nfhVient to affect the conditions necessary to the ] existence of this oceanic bird. It has not been honed down like the Dodo and Dinornis. The numerous bones on the shoresof Greenland, Newfoundland, Iceland and Norway, attests its former abundance; but within the last century it has gradually become more and more scarce^ and finally extinct. There is no better physical reason why some species perish than why man does not live forever. We can only say with Buffon. " It died out because time fought against it." From the Lingula prima, to the Auk,

SHEARING OR CLIPPING ANIMALS AND
SKINS.

CHAPTERS

CATEA

aener» have been constantly losing species, and «pecies varieties; types and links are disappearing.

THIS invention, patented by E. H. Rawüngs,
of Paris, relates to a shearing apparatus of
the class in which the hair or wool is cut. by a
reciprocating knife working upon the surface of
a comb, and consists, 1st. In the peculiar forma-
tion of the comb; 2nd. In the employment in
combination with the comb and knife of a
novel device for keeping the knife properly and
evenly in contact with the comb; and 3rd. In
the mechanism for imparting motion to the said
knife. Fig. 1 is a top view; Fig. 2 is a similar
view of a modification of the same. A is the
comb or toothed plate, and B is the knife which
has two cutting edges; C and D are the handles
whereby the apparatus is held and operated ; E
is a bridle or bridge which is placed over the
knife, and is so formed and arranged that the
knife works in contact with its under surface,
and is thereby kept evenly in contact with the
comb throughout the extent of its course ; F is a
toothed segment pinion to which the knife is
fitted and secured by the screw F , the latter is
secured in the plate A, and may be readily re-
moved when it is desired to change the knife.
The pinion F is geared into the segment G, which
is attached to the plate A by the screw H,
whereon it is fitted to work freely. To the seg-
ment G is connected one end of the rod I, whose
other end is attached to the elbow lever D1, on
which is fixed the handle D. The bridle or bridge
E is secured at each end to the plate A by screws
E', between whose heads and the bridle are spring
washers, and the pressure of the said bridle upon
the knife may be regulated by adjusting these
screws. The stroke of the knife is limited in each
direction by the stops J fixed in the plate A. By
means of the comb or toothed plate A the hair
or wool of the animal to be sheared is raised, and
the toothed part * of the said plate is so formed
and arranged that the knife at the commence-
ment and end of its course in each direction lies
entirely beyond such toothed portion, as shown,
so that the hair or wool may be taken np without
obstruction between all the teeth from one end to
the other thereof, and so that no hair will remain
caught between the teeth and the knife when in
the operation of shearing the Apparatus is raised or
moved backward orforward. The handle С serves
as the means for holding and guiding: the appa-
ratus with the left hand, while motion is imparted
to the knife through the connecting rod I by the
lever D> and handle D. Pressure of the knife
upon the oomb is produced by means of a spring
washer placed at the axis or centre thereof, which

ON CURIOUS
PILLARS.

MAY.

By J. R. S. Clifford. -. .-AKING due allowance for the difference jVX between early and late seasons, we shall find that caterpillars generally are more abundant during May than at any time during the spring and summer season. These, having at tained maturity, pass into the chrysalis state, and undergo one of two destinies—they either appear, as perfect insects some time dur the autumn or put in an appearance in the early spring; or, almost, perhaps, before we can say it is spring, though an occasional twitter of the bird, or the swelling buds on shrub or tree hint to us that the vernal time is approaching. Of this latter class is the moth of which the transformations are now described, its time of appearance being February, or the beginning of March. During the mouth of May, in those places whoro the species occurs, the caterpillars are sufficiently conspicuous from their mode of life to attract the notice of observers who are not entamologically inclined. The small Egger Moth {Enogastcr lanettrUX to which we have been alluding, deposits its eggs on the twigs of the hawthorn, and it would appear as if usually the whole number of eggs which each female is possessed of are placed in one' pot. These eggs are covered with down, which the parent strips off the abdomen, its hue being blackish, or smoke-coloured, luie, serves to protect the eggs from the rain and cold of the season, and when April arrives, the young .11 i :- *rt ',"trash ont. linvîner sometimes

caterpillars begin to hatch out, having sometimes a difficulty in disengaging themselves from their downy envelopment. In habit they are gregarious nearly throughout their life, constructing a nest or web, in which they repose, and devour the leaves around it, extending their excursions by degrees to some distance from this home. As they increase in size, with successive changes of skin they remove from place to place, constructing new abodes, until the tiny nest, which at first might have been hidden in the palm ot the hand, gives place to a structure of some size, which the insect hunter pounces npon with satisfaction should he come across it. In this common nest they generally contrive to include one or two largish branches, on which they cluster when not eating, lying extended at full length. If one of these caterpillars is alarmed, he suddenly raises the head and the front segments, assuming «onie

what of the attitude of the Hawk Moth Caterpillara, and if still further disturbed, then falls с impacted into a ring. After the lagt ehange ef skin, the caterpillars of the Small Egger separate and feed alone, but it would seem аз if this were not invariably tbc case. The general colour is relvety black ; along each side there runs a narrowiah yellow stripe, from which, on each segment, a slender branch goes off at a right angle; the body is clothed with hairs of two different lengths, the shorter hairs being rich brown, the 'onger paler, with greyish tips. The lege and the hindmost pair of claepers are black, the rest of the clampers beiog red. The cocoon formed by this caterpillar has piren its name to the moth; it is egg-shaped and compact, and so small, as compared with the size of the caterpillar, that it is difficult, when the two are placed together, to imagine how it can be constructed, as the caterpillar mu-t, of course, work at it from the inside. Not only, however, does it complete this cocoon in the most perfect manner, but it leaves, with great dexterity, two or three small holes in this encasejncnt, the purpose of which is doubtful.

Another interesting Egger caterpillar may be discovered at this season by those on the sea coast, especially in the south of England. Some time in August, the female moths of the Grass Egger {Bombyx trifolii) drop their pale brown eggs at random amongst the herbage. These produce caterpillars in the course of a week or two, not easily to be found during the autumn, since they keep close to the ground. Feeding again in the spring, they are of some size in May, being full-grown at the beginning of June. When found on grasses they are generally observed to eat from the tip downwards. Though known as the Grass Egger, an observer who has bred many, states that they thrive on the birds' foot trefoil, and will alsoeat oak,willow, bramble, and furze. Mr. Newman, on the contrary, found that all the individuals he had in his cngcs refused to eat anything hnt grasses. Like the preceding sjiecies, the ground colour is an intense black; though in this caterpillar there is a triple series of very small white spots along the back, which are best seen when the caterpillar is rolled into a ring, as is its habit when annoyed. Ou the third and fourth segments is an orange mark in the form of a crescent. The body is covered densely with soft hairs. The cocoon ie asnally placed amongst the sand (for the species occurs on the very margin of the sea), being attached slightly to the roots of the grass; it is brown and compact.

One of the largest British moths belonging to the family of the Bombycrt is that known as the Lappet (Lasiocampa qvweifolia), and this name is taken from the enrions appendages or "lappets " which adorn the body of the caterpillar. This creature lives through tho winter, being then only about an inch in length, but in May it has usually attained its full proportions. It ocours on blackthorn, willow, and sometimes on oak, being rather easy to detect from its size, though not by any means common, as far as oar experience goes. The Rev. J. L. Wood, however, asserts that he has no difficulty in getting either caterpillar or moth whenever he requires it; but he loaves the mod«» rpcrandi for the ingenuity of his readers to discover. Different specimens of this caterpillar vary much from each other in colour, being various shades of grey and brown ; on the twelfth segment there is a distinct hump, and along tho sides the protuberances which give it its rather fanciful name; between the second and fourth segments are two broad stripes of a bluish purple. The» cocoon is placed by the caterpillar low down amongst the herbage ; it is not egg-shaped, being long and blackish, and within it is swung the chrysalis, which is also black and smooth. The moth is sluggish, and when nt rest very much resembles a dry and faded leaf. When fresh from tho chrysalis, it has a beautiful bloom upon the wings, which faides in a few hours.

Amongst the butteafly caterpillars, which, fonnd at all, are most likely to turn up in good'}' numbers from their peculiar habits, are those of the three smaller Fritillaries belonging to the genus Melitœa. These are mostly fuli-grown about the beginning of May. The commonest is the Greasy Fritillary (ilf. Artemi»), which occurs in damp, low-lying meadows. A year or two ago, as an entomological friend reporte, these caterpillars occurred by the thousand in a certain part of Ireland, and were looked upon as a phenomenon by the country folks. Thoy feed by preference on tho plantain, sometimes also on the

"devil's-bit scabious." The winter is passed by them in a state of hybernation, under the protection of a silken covering; in the spring, however, they feed exposed, and seem even to delight in the rays of the sun. The caterpillar* of the Greasy Fritillary are black, or deep brown, with reddish-brown clampers, the surface of the body is sprinkled with white dots, and i« ateo covered with spines rather thickly sal In the •' good old times," this insect occurred at Chelsea, in the immediate vicinity of London; it must now be sought in localities remote from the metropolis. The butterfly flies very tardily, and may be easily caught with the hand.

Mr. Newman has described with sreat acumen the history of the Heath Fritillary (iff. Athalia)—so called because it is most partial to heathy spots in or bordering npon woods. The eggs are laid by the parent butterflies in June and July on the narrow and broadleaved plantain, and the young caterpillars after feeding a short time, hybernate early cloee to the roots. As soon as their food plants are in leaf they feed again, and continue to feed until the plautain is in flower, which flower, Mr. Newman notes, they much resemble in colour, and thus escape some of the assaults of bird", so frequently destructive to caterpillar life. These caterpillars, like those of all the Fritillaries, are studded with spines, some of which are orange and white, and other, pure white with black tips ¡ the ground colour being black, on which some snow-white dots show conspicuously, the under surface is of smoky hue. The chrysalis is short and stoat, and attached by hooks to a little web of silk previously spun by the caterpillar. The Ghmville Fritillary (ЛЛ Cinxia) resembles the preceding in its habits, and occurs in tolerably plenty on the Undercliff, in tho Isle of Wight, appearing to have a preference for rough ground. Mr. Dawson remarks that, by natural instinct, the caterpillars of this species, when young, feed low down on the banks, where the growth is most luxuriant, and they are sheltered from rough weather ; and as they increase in size they advance higher up the slope, attacking the older plants, to the stems of which they attach themselves, and become chrysalides.

Amongst the crowd of caterpillars whioh may be beaten from the hawthorn hedges this month, we are almost sure to find the small, but singularly-formed caterpillar of the Chinese character ( Cilix «pínula), the perfect insect being adorned with silvery scales, supposed to resemble Chinese letters—hence tho name. The head of this little caterpillar has a crown, which is cleft in the middle; the body is of a dull brown colour, wrinkled, and having a stripe down the back, and some wavy markings. There are also numerous warts, some largish, some minute; a hump on the eleventh segment, and at the extremity of the body a terminal spike, the hindmost claspers being wanting. This spike is raised in the air, and carried much in tbc position in which the Puss Moth caterpillar raises its horns. When full-grown, the caterpillar of tho Chinese character constructs a small gnmmy cocoon, which is ingeniously hiddan in the angle of a branch or twig. There are two annual broods, and the second usually appears in Angnst or September, remaining as a chrysalis through the winter.

Notable among the insects haunting the vicinity of the metropolis of England, and especially abundant in its northern suburbs, is the moth rather absurdly called the Willow Beauty (Boarmia r/wmboidaria), which may be seen sitting qnietly in the daytime with expanded wings on walls or old palings. The caterpillars which produce this species are usually adult in May, feeding on the ivy, and giving preference to the large-leaved kind, known as Irish ivy. The eggs are deposited in tho summer in little clusters, and the young caterpillars, when newly hatched, cat only partially through the leaves, and, keeping on the underside, aro thus protected from the weather. In about a fortnight they begin to nibble holes in the leaves, bnt long before winter approaches they conceal themselves amongst the recesses of the ivy, spinning a slight web, to which they fix themselves firmly. These caterpillars feed again in April, and when of full size enter the earth, and change to chrysalides just beneath the surface. The colour of the body is brown, darker or lighter, in different specimens; there are four black dots on each segment, the head is rather darker than the body, notched on the crown with two palemnrks, which look like eyebrows. When touched, one of these caterpillars falls at first by a silken thread, and then de

scends to the ground, feigning death. When resting, the body is extended in a stick-like position.

One of our most active moths is that appropriately called the July Highflyer ( Tptipite» tlutata), and the habits of the caterpillar producing it contrast singularly with those of the mature insect. This lives through the winter, and feeds up in the spring, being full-grown in May. It lives upon the sallow, generally hiding during the day in the masses of seed-down^«eBj_ coming forth at night. It is slow in its aiove-¡ meats, and falls at once, as if inanimate, when it is touched. The colour is pale brown or smoky brown, the body being marked with white stripes, same of which are indistinct, and it is slightly attenuated towards the head, which ¡з clear brown, with blackish cheeks, and slightly notched above. The chrysalis is placed in a cell constructed in the seed pods of the sallow, from which the moth appears in July and August, and flies at times briskly in the sunshine.

GEOGRAPHICAL INFORMATION.
Lntbodcctoby.

THESB notes, articles, or whatever naufe my readers like to give them—do not profess to be original. They will be simply compilations condensations from more elaborate treatises. Of conrse I have an aim ; and it is this—to give our superabundant population, oar intending emigrants, some bonùjide knowledge of the different lands at the present moment open to settlement. The English Mechanic having an immense circulation, and being read by that class to which geographical information seems all-important, I have determined, with the Editor's sanction, to extend far and wide such facts relating to this subject as are at present known to a select few. The peculiar information required by intending emigrants cannot bo gathered from any existing text-books, but is contained either in the minds of returned settlers and traveller!, or scattered throughout a number of costly volumes beyond the reach of any but the rich. The so-called guide books are often terribly inaccurate, as will be best seen from the sensible remarks made in he following extract :—

"I greatly doubt," said P , as we strolled

away, " the advisability of glossing over all drawbacks (many, very man v of which exist) to the intending emigrant. Better far to place tho colouring in a fair light, to speak freely of the difficulties he must encounter in soil and climate, and suggest a remedy. A poetical description ot scenery in a guide-book may serve to cover over poverty of soil ; but tho truth is, that the emigrant can't see the poetry of the thing when his crops fail, and then he becomes disgusted with the land of his choice."

The colony is generally represented in an ideal light, as one would wish it to be, but not as it really is. Guide-books, as a rule, omit the failures, giving only one side of the question. This is not the place nor the time to write a dissertation npon emigration; it is a fact that our fellow citizens are emigrating; many Ьате already gone, more are preparing to go. Hard it is to leave old associations, to leave home, kindrsd, all that is dear, in order to fight the battle of life in a far-off country; but necessity knows no law. Starvation stares us in the face here: affluence, or at least plenty and prosperity are promised there. Nevertheless, an emigrant who would fail to gain a livlihood in one place may become rich in another. Different men are adapted to different countries, and although the Caucasian seems to flourish everywhere, yet it is not so. In India, part of Africa, the " workers" are not the sons of previons workers, but fresh arrivals from the Old Country. An Englishman's childrens' children would soon imbibe aud be enervated by the peculiar climatic influences of these regions, but other parts have a climate very similar to our own, and here it is that the race is perpetuated. America, Australia, New Zealand, the Cape, &e., all testify to this fact. Following the example, therefore, of " F.R.A.S.," I shall be glad to answer, when possible, any questions, directed to the Editorin the nsual manner. This I think, will bo the best course to pursue, as although many readers would enjoy a descriptive narrative of the journey of Mr. Freshfield amidst Caucasian mountains, or Mr. Williamson in Marchuria, &c, yet the specific object at which I aim would not be gained. F.RO.S.

EXHAUSTED TEA LEAVES.

UNDER any circumstances, it is a misnomer to call infused tea leaves "exhausted," as they still contain a large proportion of such material as we every day consunio in the form of bread, beef, and vegetables—viz., in Souchong, 40 per cent., and in Gunpowder, 4-40 per cent, of nitrogen. It needs but a glance to see that, apart from any putrefactive decomposition which may be discovered in re-dried tea leaves, they are not unfit for human food, if consumed as a vegetable. The use of leaves which had "passed through the pot," as a means of increasing the bulk of tea retailed by certain grocers of "easy virtue," was conspicuously brongbt before the nublic by Mr. Phillips, of the Inland Revenue Office, twenty-six rears ago. He then remarked :—''In the year 1843 there were many eases of re-dried tea leaves, which were prosecuted with viguor by the board, aid the result was, to far as we could ascertain at the time, the suppression of the trade. It was supposed, in 1843, that there were oight manufactories for the purpose oF re-drying exhausted tea leaves in London alone, besides several others in various parts of the country. The practioe pursued was as follows :—Persons were employed to buy np the exhansted leaves at hotels, coffee-houses, and other places, at 2Jd. and 3d. per lb. These were taken to the factories, mixed with a solution of gum, and re-dried. After this, the dried leaves, if for black tea, were mixed with rose-pink and black lsad, to 'f»ce ' them, as it is termed."

In those duvs.it will be remembered, owing to the cm>rmously-increasing consumption arising from various causes, the inducement to adulterate was much greater than it is now, and the duty levied waj is. 24d. per lb. Coming to a more rec»nt period, we find that on the 18th December, 1850, the excise authorities seized a quantity of material in Liverpool, expressly prepared for tea adulteration, which possessed the negative merit of containing no tea at all. It consisted of broken sycamore and horse-chestnut leaves, stuck together I'.nd rendered astringent with catechu. During the following year another pleasant little episode in the way of sophistication came to linht in the classical region of Clerkcnwell. The Times of May, 1851, gives a description, which we abreviate :—" Edward South, and Lonitahis wife, were charged with being concerned in the manufacture of spurious tea. The officers hod been to their house,where they found the prisoners engaged in the operations. There was an extensive furnace, before which was suspended an iron pan, containing sloe leaves and exhausted tea. leave-, which they were in the practice of purchasing from coffee-shop keepers. On searching the place, tkey found an immense quantity of used tea, bay leaves, etc., for the purpose of manufacturing illicit tea, and these were mixed with a solution of gum and a quantity of copperas. The heat was so excessive that the officers could scarcely remain, bnt the prisoners did not seem at alloppressed. The woman was employed stirring tho bay leaves and other materials with a solution of gam in the pan; and in one part of the room there was a large quantity of spurious stuff, the exact imitation of genuine tea. In a back room, were found nearly 1001b. weight of re-dried tea leaves, bay leaves, and sloe leaves, spread on the floor, drying. The prisoners had pursued their nefarious traffio extensively, and where in the habit of dealing largely with grocers, chandlers, and others, especially in the country."

That such vile practices are by no means obsolete, we observed from one of the occasional notes in the first number of this journal; but it is to be hoped that public indignation, once more aroused, will have the effect, through judicious legislation and the continual employment of analytical chemistry, of curbing, if not altogether eradicating, tea adulteration.

Already ibe common ity feels the sting, and it is a significant fact th.it the 7,000,0001b. of trashy tea, alluded to in Dr. Lethoby'B report as beiDg under the ban of the City authorities, almost exactly correspond with the quantity of good tea short last year in the imports from China, as compared with those of 1868.

It must be evident from the foregoing, that the time has passed away when wo need hold np our hands and roll onr eyes in holv horror at the iniquity of the Chinese. Surely it were better to mingle our frugal Congou with Maloo mixture, over which the nimble Shanghai pigs had gyrated, and China dogs gambolled, rather then return to the days of slow poisoning by arsenite of copper, chromate of lead, bay leaves, Bioo leaves, and catechu.—Food Journa 7.

DRESSING MILLSTONES WITH THE DIAMOND OR " BORT."

OUR readers have observed that for some weeks past an interesting controversy has been sustained in our columns on dressing millstones. Who would have thought that the English Mechanic would have become nn organ for millers? Judging from what several correspondents have said, such is the case. As the question is an important one, not only to millers, but to all interested in tho cheapness and purity of flour, we will transcribe from the Kngincer a paper on the subject.

A remarkable revolution has been in progress during the last' two years in a department of the mechanical operations connected with the manufacture of il>ur, and various facts associated therewith are worthy of record, not only on account of Ml e importance of ihe manufacture, as supplying the "staff of life" for our daily wants, but also because they possess considerable interest from a mechanical point of view. We do not proposo to enter very minutely into detail, nor to deal very largely with technicalities which could interest the miller only: at the same time we may have to mention some facts that are most probably known to all our readers.

The character of the grinding surfaces of the millstones has a great deal to do with the quality of the flour produced. After the grinding operation, the flour is separated bv "dressing" or silting, into different qualities, and from the same grain one pair of stones will produce a much larger proportion of the first and finest quality than another pair. This depends on the "dress " or surface condition of the stonos. The face of each stooo has a number of grooves or "roads " formed upon it, thosurfaces or " lands" between these grooves beiug the parts which effect the grinding operation. It has hitherto been the practice to produce on the lands the roughness necessary for grinding entirely by hand, by means of a steel chisel, pick, or bill; and considerable skill is required by the operator or "stoneman," who strikes in a peculiar manner and so as to just crack the Biirface of the stone. The roads of the stone are arranged in sectors, all in one sector being parallel to each other, and the " master " or longest road in each sector being in a radial position. This arrangement is, however, sometimes departed from. The cracking or dressing is generally done in lines which are parallel to the roads, and at minute distances apart.

Millstones when grinding night and day are usually re-dressed by tho handbill onee in six days. In large mills the stonemen are kept exclusively at the work of dressing, and in consequence attain as great efficiency as is possible at this description of work. In small mills, however, such as are scattered over country districts, this is not possible, as the men cannot wholly oocupy themselves with dressing, but have to attend to all sorts of work, and cannot attain the same proficiency. With the best and most careful hand-dressing possible, the millstones, for from thirty to forty hours after being drcsBed, cut up the wheat very much, making the meal rough and unequal,—the flour being in conseqnenoe speeky and irregular, the bran small and badly cleaned, and the proportion of flour-sharps, middlings, or second quality, large; and in proportion as tho millstones arc less perfectly dressed those evils increase. In addition to the importance of the dress or cracking being well done, it is also of groat importance to have the millstone face, or grinding surface, absolutely true and level; much difficulty, however is experienced in keeping the millstones true—the tendency being for a portion or Bection of tho grinding surface to get out of truth with tho rest. Indeed, under the system of hand-dressing it has been found impossible to prevent this evil from arising, more or less, notwithstanding the most careful use of the proving-staff. The application of tho staff to the surface of the stone is the only means hitherto in use for testing or indicating the truth or level of millstones, and it has long been felt to be imperfect, a more thorough and accurate method being much wanted. Many practical and careful millers consider the truth

and level of the millstones as of more importance even than the quality or perfection of the cracking or dress, and recent experience with improved arrangements has very much tended to confirm this opinion. We feel sure thnt every miller who has given tho matter consideration will agree with us that these two defects are all but inseparable from the system of dressing by hand—namely, an imperfect dress and a waut of truth and level in the millstone face.

It is roughly estimated that there are 80,00(1 pairs of millstones in the United Kingdom, so that the importance cannot be over-estimated of any sound improvement so essentially affecting their use aud action as one relating to the "dressing " of their grinding surfaces. The subject has not failed to attract the attention of inventors aud patentees, and a great variety of appliances have been proposes from time to time. Amongst these there have been various combinations of mechanism which, in imitation of tin; ordinary hand-dressing, have been designed to actuate a steel bill or pick, the objects of snch mechanism being to render the action more uniform and regular, ami to dispeus.; with extreme skill on the part of the operator. Some of these combinations have comprised arrangements for making the lines of the cracking accurately parallel and at uniform distances apart; but in none of those designed for using the" steel tool is there any provision for, or arrangement conducive to, the maintenance of the truth and level of the stone ; and as none of them have come into use, it may be safely assumed that they have uot satisfied the requirements of the case.

No attempted improvement in dressing millstones hus as yet attained any practical sucoess that has not comprised the use of "borf'for the cutting tool; at the same time, it may be interesting to refer to one of the machines proposed for operating with a steel bill, as not only was it anterior to any proposal to use the diamond or bort, but it also contained various mechanical appliances, which, with suitable modications, have been adopted in tho successful bort machines, and its designer may, therefore, justly claim to have contributed something towards the ultimate success. The machine to which wo refer is the invention of a Parisian miller, P. J. Morisseau, patented in this country in the name of G. Davies, of Serle-street, ou the 9th April, 1801, No. 8Gu, and is shown in vertical section in Fig. 1. and in plan in Pig. 2. The following description is from the specification :—

"The machine rests by its own weight upon that part of the millstone A, which it is desired to operate upon, and it may be moved with ease on to any portion or divisionof the circumference of the stone, being guided in this movement or alteration of position by mentis of two uudgcons or pins fixed at two extreme points of the frame 13, and sliding in a circular groove a, made in the iron ring C, which embraces the circumference of tho millstone, aud is adjusted and fixed thereto by set screws.

"Each of the longitudinal sides of the machine is provided with a long screw rod 4, upon which is mounted a bevel wheel e. Those wheels have bosses screwed internally, and work between two projecting pieces forming part of the frame or oarriage D. Tbis carriage also supports a long ratchet or grooved cylinder U, extending the whole width of the machine, and to the extremit:ei of which are keyed hovel pinions e gearing respectively with the wheels e on the screws b. it results from this arrangement that by the rotation of the cylinder E the oarriage D can bo caused to travel tho whole length of tho screws b, and consequently of the machine itself. ()o the carriage D are two brackets or supports carrying a shaft/, which is grooved throughout its eutirc length so as to receive a key connecting a cum Ij thereto, which cam is intended to communicate motiou to the cylinder E, as hereafter described. Tbis cam is held between two projections or bosses g\ fixed on a second carriage F, which carries the cutting tool or hammer m, and also serves as its guide. This carriage, which is mounted on y slides on the carriage D, is moved by hand by the workman by the aid of a lever h. and can bo slidden from end to end of tho machine, and arrested at any point dosired. The tool earlier k moves vertically iu V slides formed in trout of the carriage F for that purpose; to this piece are attached jaws which hold tho cutting tool or hammer m, the position of which latter can '«' regulated to any height desired above tho sin

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