THE TORTOISESHELL OF COMMERCE. 375 



The imports of borax and tincal into the United Kingdom since 1853 

 have been as follows, in cwts. : — 





Tincal. 



Refined Borax. 



Boracic Acid. 



1853 



10,803 



2,262 



20,793 



1854 



14,456 



2,164 



24,839 



1855 



16,765 



704 



27,808 



1856 



13,984 



4,651 



26,827 



1857 



13,390 



6,674 



25,687 



1858 



2,800 



2,111 



26,263 



1859 



4,136 



1,707 



35,927 



The tincal and refined borax all come from India, and the boracic acid 

 chiefly from Tuscany. The boracic acid crystals are far from pure, contain- 

 ing a small quantity of numerous sulphates mechanically mixed. Those 

 interested in the manufacture and supply of boracic acid from Tuscany, 

 where it is all made by Count Lardarel, who chiefly supplies the English 

 market, and M. Durval, who exports to France, will find some descriptive 

 details of the lagoons from which it is obtained, and the mode of manufac- 

 ture, in the 8th vol. of the ' Journal of the Society of Arts,' p. 542 (No. for 

 May 25, 1860). 



THE TORTOISESHELL OF COMMERCE. 



BY THE EDITOR. 



The term tortoise is applied in science to those land and water animals 

 which form the first order of reptiles, and are characterised by an external 

 bony envelope, covered with a horny or leathery sheathing, and enclosing, as 

 in a box, the internal organs and other portions of the osseous framework. 

 The common name of turtle is often given, but not commercially, to the 

 marine tortoises ; and it is these with which we have at present to deal. 



The broad, horny plates which cover the dorsal buckler or carapace of 

 the sea-tortoise are in some species so fine and of such beautiful colours 

 as to be employed for various purposes of art. There are usually thirteen 

 of these epidermal plates on the carapace or back, and twenty-five mar- 

 ginal pieces, or those round the edges. The tortoiseshell of the hawk's-bill 

 turtle (CIcelonia imbricata of some authors), and of the Caret of the French 

 (C'helonia Caretta), is that most esteemed, the plates being stronger, thicker, 

 and clearer than in any other species. Of the thirteen largest plates, called in 

 trade the " head," there are four on each side, and five on the back, the 

 last bent in the centre. Of the side plates, the two middle are the most 

 valuable, being largest and thickest ; those on the back, and on the margin, 

 denominated hoofs or claws, are comparatively of less value. The lamellae 

 or plates vary in thickness from one-eighth to one-quarter of an inch, accord- 

 ing to the age and size of the animal, and weigh from four to six pounds or 

 upwards. The larger the animal, the better is the shell. 



