March 2, 1899] 



A'.^ rURE 



425 



similar in the two plates. Moreover, the author states that the 

 forms shown on his plates agree very closely with those 

 obtained by Prof. Barnard in 1893 ; so that there being at least 

 three photographs showing identical forms, the evidence is greatly 

 in favour of their being true cosmical matter, as it is incon- 

 ceivable that chance markings could exhibit such coincidences. 

 To explain their absence on Ur. Roberts's plates, the author 

 thinks that the atmosphere at Goodsell Observatory must be 

 much clearer than is the case in England, giving as his reason 

 the fact that the star images on his plates are much less sur- 

 rounded by atmospheric glare than those of Dr. Roberts. 

 Indeed, even with the long exposure of over eleven hours, the 

 star discs are still easily discernible on the reproductions, 

 showing that the observing conditions must have been extremely 

 perfect. 



Meteor Photogr.M'HY, — Those who may be interested in 

 this branch of astronomy will find the illustrated description, by 

 Mr. W. L. Elkin, of the apparatus used for this purpose at the 

 Vale University of considerable value (Astrophysical Journal, 

 vol. ix. p. 20, January). 



The instrument consists ol a long polar axis, driven by clock- 

 work, and provided with means of attachment for from eight to 

 twelve cameras round its circumference. The lenses used for 

 this purpose are selected for their rapidity ; hence we tind that 

 portrait lenses are in nearly all cases chosen. During the last 

 November Leonid shower eight cameras were used with the 

 instrument ; six of these carried portrait lenses of from six to 

 eight inches aperture and from twenty-seven to thirty-six 

 inches focus, the remaining two being provided with lenses four 

 inches in diameter. 



It is, however, not indispensable to have an expensive clock- 

 driven mounting, and for the same meteor shower a simpler 

 apparatus was also used, having a wooden polar axis turned inter- 

 mittently at intervals of ten minutes by means of a toothed 

 wheel. By also displacing the axis slightly at each movement 

 of the wheel, the successive star trails fell alongside each other, 

 making a kind of time scale, which made it possilile to refer 

 any meteor trail to its position among the stars if the time of 

 its appearance had been noted. 



The article is illustrated by a photograph of the instrument in 

 position at the observatory, and one of the successful plates 

 .showing a Leonid passing near Mars and the star-cluster 

 Prnesepe. 



THE TRADE IN TORTOISESHELL. 

 \ MONG the number of misnomers current in popular 

 ■^ language, and more especially in that relating to natural 

 history, few are more unfortunate than is the application of the 

 term " tortoiseshell " to the substance which should properly be 

 designated turtleshell, or perhaps rather turtle-skin. It is, 

 however, far too late in the day to attempt a change ; tortoise- 

 shell it always has been, and tortoiseshell it will doubtless 

 remain. In its manufactured state, whether in the form of 

 inlaid buhl-work, as the handle of a fan, or as a comb, the 

 translucent plates of tortoiseshell. with their rich mottlings of 

 golden yellow and warm chestnut, are familiar to all. The 

 particular species of reptile, or reptiles, from which it is 

 derived, the part that it plays in the economy ofthe.se creatures, 

 and the methods of the manufacture, to say nothing of the 

 enormous volume of the trade, are, however, less matters of 

 common knowledge. 



To begin with, tortoiseshell, in the widest sense of the term, 

 may be taken to include the horny superficial plates or shields 

 overlying the bony case of the great majority of tortoises and 

 turtles, although in the popular and trade sense it is restricted 

 to those of the latter. Anatomically it corresponds to the scarf- 

 skin or epidermis of the human integument, the underlying 

 bony case or shell representing, to a great extent, the true skin. 

 Turtles differ from tortoises, among other features, by the 

 heart-shaped form of the upper half of the shell, or carapace, 

 and the conversion of the limbs into paddles adapted for 

 swimming. The upper part of the shell carries a median row 

 of five large superficial horny plates, flanked on each side by a 

 row of four or five still larger flat plates ; these thirteen or 

 fifteen large plates, affording some of the most valuable com- 

 mercial tortoiseshell in the particular species whose " shell " is 

 most in demand. On the front and hind edges of the upper 

 bony shell and the portion connecting the latter with the 

 plastron, or lower shell, are a series of smaller horny plates, 



NO. I 53 I, VOL. 59] 



generally twenty-four in number, which are .sharply bent in the 

 middle, and are known in the trade as " hoof." They form the 

 least valuable portion of commercial tortoiseshell. The under 

 surface of the sjiell of a turtle carries six pairs of large, more or 

 less flat, horny plates, for which the trade term, derived from 

 their uniform colour, is "yellow-belly." In value they some- 

 times exceed all but the very finest of the large upper plates, 

 generally known simply as "shell." The term "shell" has 

 thus a very different signification in commerce from that which 

 it bears in natural history, where it is applied to the whole 

 solid case of the reptile, including both the overlying horny 

 plates and the subjacent solid bony structure. 



Of the host of land and fresh-water tortoLses, most of which 

 are of comparatively small size, the horny plates (which, by the 

 way, are altogether wanting in the so-called soft tortoises of 

 tropical and subtropical rivers), on account of their thinness and 

 opacity, are now of no commercial value whatever, at least in 

 England. 



Moreover, it is by no means all the species of marine turtles 

 which yield commercial tortoiseshell. Of these marine turtles, 

 exclusive of the great leathery turtle, which has no horny plates 

 at all, there are three well-marked and perfectly distinct types, 

 severally represented by the green, or edible turtle, the hawks- 

 bill, so named from the form of it.s beak, and the loggerhead. 

 The latter, which is the largest of the three, taking its name 

 from its huge ungainly head. Of the green turtle the plates are 

 so thin and so badly coloured as to be of little or slight manu- 

 facturing importance, so that they do not apparently figure at all 

 in the trade circulars of Messrs. Lewis and Peat. In this 

 species the horny plates on the back, which have a dull pale 

 brown groundcolour with streaks of black, meet together by 

 their edges, like the tiles in a pavement, or the plaque's in a 

 mosaic. On the other hand, the much thicker and more beauti- 

 fully-coloured plates on the back of the hawksbill, which afford 

 the most valuable commercial shell, overlap one another like the 

 slates on a roof during the greater part of their owner's life, 

 although in very aged individuals they are joined by their edges. 

 The largest and best plates, which are those in the middle of the 

 sides of the back, are about a quarter of an inch thick in the 

 centre, and measure about thirteen by eight inches ; their 

 weight being from about half-a-pound each to as much as one 

 pound. Their translucency and beautifully mottled colours have 

 been already mentioned. The lower plates, or " yellow-belly," 

 on the other hand, are of a uniform golden yellow tint ; while 

 the connecting marginal plates, or " hoof," are partly plain 

 yellow and partly mottled. In size the hawksbill is somewhat 

 inferior to the green turtle ; the length of the carapace being 

 about thirty-two inches in the former, as against forty-two in 

 full-grown examples of the latter. Both are found in all tropical 

 and subtropical seas ; and both resort to flat sandy shores for 

 the purpose of depositing their eggs. 



From a dead turtle the plates of tortoiseshell can be readily 

 detached from the underlying bony framework by the appli- 

 cation of heat. Sometimes boiling water is used, but more 

 generally the whole shell is placed over a fire. In the West 

 Indies one method, which may or may not be still in use, was to 

 bury the whole shell in the ground for ten or twelve days, when 

 the plates became readily detachable. It is stated, however, 

 that the removal is too often effected by the cruel method of 

 applying heat to the living animal, afier which the unhappy 

 turtle is returned to the .sea to grow a fresh suit of plates. 

 Formerly it appears to have been the custom to bore each plate 

 of the upper' shell, and to fasten together the whole series 

 furnished by each individual turtle with wire or string ; such 

 bundles being sold together. Now, however, the samples 

 offered at the London sales on string or wire are comparatively 

 few, although the practice is maintained with Mac.issar and 

 S' imetimes Ceylon shell. 



In the trade circulars of Messrs. Lewis and Peat, hawksbill 

 tortoiseshell is divided into the following geographical classes, 

 viz. : (i) West India ; (2) Zanzibar and Bombay ; (3) Mauritius 

 and Seychelles; (4) Singapore and Macasar : (5) Sydney and 

 Fiji ; and (6) Ceylon. Most of these classes are again sub- 

 divided into "shell," "yellow. belly," and "hoof"; while these 

 latter subdivisions are again split up according to size, thick- 

 ness, colour, and condition. Nos. I and 2 always send very 

 arge imports ; next come Nos. 4 and 5, which, however, 

 exhibit very marked seasonal oscillations; while those of Nos. 

 3 and 6 are much smaller. 



In order to ascertain how the trade of the present day in this 



