On the Economical Uses of some species of Testacea. 63 



tween them ; each membrane has a corresponding coat or crust of 

 carbonate of lime, secured by a new membrane; and each coat of 

 lime is so situated that it is always between every two membranes, 

 beginning with the epidermis, and ending with the last formed inter- 

 nal one. The animals which inhabit these stratified shells, increase 

 their habitation by means of a stratum of carbonate of lime secured by 

 a new membrane, and as every additional stratum exceeds in extent 

 that which was previously formed, the shell becomes stronger in pro- 

 portion as it is enlarged ; and the growth and age of the animal may 

 be denoted by the number of strata, which concur to form the shell. 

 Pearls prove also to be similar in composition to the nacre, and they 

 appear to be formed of concentric coats of membrane and carbonate 

 of lime. The wavy appearance and iridescence of mother of pearl, 

 and of the pearl itself, are evidently the effect of the lamellated 

 structure and semi-transparency. On dissolving the lime t)y acid, 

 the animal frame-work of the shell is left exposed.* 



Fisheries. — In the older writers, the following mode of catching 

 this fish is given, and though it differs in some respects from the la- 

 test accounts, yet the difference may probably be owing to the lapse 

 of time, or from being practiced at different places. It however re- 

 fers to the island of Ceylon, though we are not told the exact part. 



There were two seasons when the shells were particularly sought 

 after, during March and April, August and September. The vessels 

 used were of two sizes, the larger carrying two divers, the smaller only 

 one. In the morning they set sail for the banks, with the land breeze, 

 which at these seasons blows regularly, and on arriving there an- 

 chored. The diver bound a stone to his body about six inches 

 thick and one foot long to enable him to walk against the water, and 

 another of from twenty to thirty pounds weight to his foot in order 

 to sink him; around his neck was a net to hold what he collected, and 

 he was provided with strong gloves or a short iron rake, to tear the 

 shells from the rocks.f His ears and nostrils were filled with cot- 

 ton, and a sponge dipped in oil was fastened to his arm that he might 

 occasionally breathe without inhaling water. J Round his waist was 



* Philosophical Transactions of the Royal Society of London, xviii. 554. Abrid. 

 Ed. 1807. 



t Chalmers' Dictionary, Art. Pearl. 



t EncyclopcEdia Americana, Art. Pearl. " According to the depth of the wa- 

 ter, the seal takes into its stomach a quantity of pebbles, as ballast, as it were, 

 being obliged to sink itself. To enable it to dive so admirably, it collects a quan- 



