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the lid is placed, surrounded by a beautifully white-beaded border, having iu its slightly raised reticulated centre the micropyle. The empty egg-shell gives a fine opalescent play of colours, while that containing the young worm appears of a brownish yellow colour. The egg of the Straw-belle moth (Aspilates gilvariu), Fig. 2, is very delicately tinted; it is somewhat long and narrow in form, with sides slightly flattened or rounded off, and is regularly serrated. The top is convex, and the base a little indented; in the latter is seen the lid and micropyle. The young worm, however, usually makes its way through the upper convex side; the indentation represented in the drawing shows the place of exit. One belonging to a very interesting class of moths, the Dingy-shears (Exarnis ypsilon), is shown in Fig. 3. A small sub-conical egg, with a flattened base, which admits of its being firmly cemented to either bark or leaf. The egg is beautifully reticulated, the ribs are slightly raised from the membrane, and connected with each other by cross-bars; they run from a marginal ring surrounding the micropyle, in regular order to the base, and a series of fine lines radiates from the central spot to the border.
An example of those eggs possessing a good deal of natural colour is shown in Fig. 10. The Puss moth (Cerura vinula), a large spheroidal shaped egg, having, under the microscope, the appearance of a fine ripe orange; the micropyle exactly corresponds to the depression left in this fruit by the removal of the stalk. The surface of the egg is finely reticulated, or rather has the appearance of a piece of netting stretched tightly over it. The colour is a deep orange. The egg of the Swallow-prominent (Pheosia dictea), Fig. 4, is in shape and size nearly the same as the former. It is spheroidal, slightly flattened at the poles, and, with the exception of one spot, that of the micropyle, the surface is a continued series of regular indentations, reminding one of those fine reticulations, or markings, seen on some of the Guiano shells. The colour is a very delicate pink. There are others rather more decided in their colour, as the egg of the Brimstone moth (Rumia cralagata), remarkable for its hexagonal reticulations, it is yellow, spotted with red; that of the Lappet moth (Gastry. pacha quercifolia), with its bluish colour, and three circular bands of brown. The Buff-tiger moth (Diacrisiu russula), Fig. 7, lays an exquisite little globular egg, the external membrane of which is covered by a fine network of irregular hexagons, which terminate at the pole in a micropyle. It has all the appearance of an iridescent minute glass globule, and is so translucent that the young worm can be seen through it. The Browntail moth (Euproctis chrysorrhæa), Fig. 12, produces a small spheroidal egg, which, slightly flattened at the poles, is
uniformiy covered with imbricated scales, and is terminated in the upper pole by a geometrical series, which fold in towards the micropyle. In every instance the worm eats its way out of the side of the egg ; the aperture is shown in the drawing; this moth appears to cover her eggs with fine hairs, and the empty spherical egg cases are beautifully iridescent. The egg of the small Emerald Volute moth (Jodis vernaria), Fig. 16, is remarkable in form, which is somewhat oval, but flattened on the broad side, of silvery whiteness, covered with minute reticulations and dots, peculiarly translucent, so much so that the little yellow-brown worm is seen curled up within, as shown in the egg to the left. At first it appears difficult to detect the presence of either lid or micropyle, and it is not until after the worm has eaten its way out that you clearly see at which end it was placed. The aperture through which it has made its escape is shown in the egg to the right. As to the change of colour (which occurs from physiological causes), connected with the development of the einbryo, a remarkable instance is afforded, and one from which the insect partly derives its name, in the Glory of Kent (Endromus versicolor). The egg is first bright yellow, then successively green, rose colour, and reddish black. A still more familiar instance is presented in the egg of the Silkworın moth (Bombyx mori), Fig. 11, which when first laid is of a delicate pale yellow, this hue it retains for some time, it is subsequently of a reddish brown, and just before the embryo quits the egg it acquires a slate colour, partaking for the time being of the colour of the embryo within ; but so soon as the worm emerges forth, the shell regains its original pale yellow. The micropyle, if that can be so called, which in this egg is a raised nipple, is in the more flattened pole of the egg. The mouth of the young worm lies towards the horn of the crescent of that pole, and it is at this point the first cut is made, just sufficient of the membrane is eaten away to admit of the head and body passing through the aperture. The outer and inner portions of the egg membrane are represented magnified 150 diameters at a and b, Fig. 11.
The egg of the small Silver-lines moth (Hylophila prasinana), Fig 9, is yellow brown, in form a truncated pyramid. The micropyle is enclosed in a regular series of radiating lines. A series of raised ribs are set in regular order around the sides, and the cross bars which connect them. These present a pretty basket-like pattern. The egg is flattened out at the base, apparently for the purpose of securing it more firmly to the leaf. The Meadow-brown butterfly (Epinephile janira), Fig. 14, lays a sub-conical egg, considerably flattened towards the apex, the raised ribs which stand away from the sides have a silvery colour, and give to the whole a corrugated appearance. The lid completely occupies the top, and in a smaller inner circle the micropyle is situated. The latter is better displayed when the lid is separated from the egg, as shown at a.
The White butterfly (Pieris brassicae), Fig. 13. The shape of the egg is very like the basket employed in lobster fishing, a rarer form than any of the preceding. It is conical, and of considerable length; the lid forms the base, which is slightly recurved upon the sides, and a regular series of ribs with cross bars run from end to end. The eggs are cemented at the base to the back or leaf of the plant in symmetrical order. In colour they are primrose.
The Brown-hair streak butterfly (Thecla betulæ), Fig. 15, presents a perfectly white, exquisitely formed, sub-conical egg; at first sight it might be compared to a beautiful ivory-turned ball in miniature. It is covered by a series of deep indenta. tions, or pits, with regularly projecting spines. The pole of this egg dips inward towards the micropyle, forming the funnelshaped indent spoken of by Leuckart. It is cemented by its broader base to the leaf.
I may remark that the specimens used for illustration were not specially selected, nor are they intended to be type representatives of the eggs of a class of insects which constitute a very large proportion of the most charming denizens of our gardens, fields, and forests. These eggs are taken from a very limited collection, and in no way do they convey an adequate notion of the variety and beauty of objects, wonderfully and curiously fashioned, no two of the species of which are to be found exactly alike. My thanks are due to my friend, Mrs. Maples, for the accurate and beautiful plate which her skilful pencil has enabled me to place before my readers.
The subscribers to the INTELLECTUAL OBSERVER will be glad to know that they can obtain most of these eggs from Mr. J. T. Norman, of City Road.
A LIST OF THE ILLUSTRATIONS.
1.-Abraxas grossularia, Magpie moth.
10. Cerura vinula, Puss moth.
15.—Thecla betule, Brown-hair streak. ' 16.—Jodis rernaria, Small emerald.
17.-Egg of Honey bee, showing germinal vesicle.
BY RICHARD A. PROCTOR, E.A., F.R.A.S.
There are, perhaps, few natural phenomena which appear less indicative, at first sight, of the operation of nature's giant forces than the downfall af rain. Even the heaviest showers—at least of those we are familiar with in England-are not phenomena which suggest an impression of power. Yet the forces actually called into action before rain can fall, are among the most gigantic experienced on our earth. Compared with them, terrestrial gravitation is more feeble than is the puniest infant compared with an array of giants. Let us look into the matter a little closely, and we shall see that this is so.
It is a common occurrence for rain to fall over an area of 100 square miles to a depth of one inch in twenty-four hours. Now, what is the expenditure of power of which such a phenomenon is the equivalent? The downfall is, so to speak, the loosening of the spring, but how much force was expended in winding up the spring ? The evaporation from the sea or from moist soils of the quantity of water precipitated, is not the whole of the work to be estimated, since the vapour has to be raised to the higher regions of the air, and to be wafted by the winds--themselves the representatives of giant forces-to the district over which the moisture is discharged in rain. But let us take this evaporation only, and estimate its real force-equivalent. It may be shown by a calculation founded on M. Joule's experiments, that to evaporate a quantity of water sufficient to cover an area of 100 miles to a depth of one inch, would require as much heat as is produced by the combustion of half a million tons of coals ; and further, that the amount of force of which such a consumption of heat is the equivalent, corresponds to that which would be required to raise a weight of upwards of one thousand millions of tons to a height of one mile! I will run briefly through the calculation by which this last result is deduced from the well-known
result of Joule's experiments that to raise one pound of water one degree Fahrenheit, requires a quantity of heat sufficient to raise one pound to a height of 772 feet; and the further experimental fact, that to raise a pound of water from the liquid to the vaporous state, requires 967 times as much heat as is required to raise the same pound one degree Fahrenheit in heat.
The amount of water required to cover one hundred square miles to a depth of one inch is, in volume
1760 x 1760 x 3x3 x 100 = 12 cubic feet, and as one cubic foot of water weighs 1000 oz., or nearly 63 pounds, we have in weight
1760 x 1760 x 3x3 x 81 x 62} pounds, and to raise this weight of water 1° F., would require as much heat as would suffice to raise to a height of one mile a weight of
1760 x 3 x 81 x 62} x 772 pounds; while to vaporize the same weight of water would require 967 times as much heat. Thus we obtain a force sufficient to raise a weight of—
1760 x 3 x 17 x 135 x 193 x 967 pounds, (that is, nearly 1,020,000,000 tons), to the height of one mile.
Such is the amount of force, whose effects are exhibited in a day's steady down-pour over a region of 100 square milesfor instance, over about one-third of Middlesex.
The same amount of water falling in the form of snow, would represent a yet greater expenditure of force. “I have seen,” says Tyndall, “ the wild stone-avalanches of the Alps, which smoke and thunder down the declivities, with a vehemence almost sufficient to stun the observer. I have also seen snow-flakes descending so softly as not to hurt the fragile spangles of which they were composed; yet to produce, from aqueous vapour, a quantity which a child could carry, of that tender material, demands an exertion of energy competent to gather up the shattered blocks of the largest stone-avalanche I have ever seen, and pitch them to twice the height from which they fell.”
But it is when we come to estimate the fall of rain as a terrestrial phenomenon-as a process continually going on over large regions of the earth's surface, as a process in which energies exhibited over one region are expended, frequently, over regions thousands of miles away-that we see the full