940 The Rev. Jous Horme’s Observations on Arragonite, 
and of course subjected to the same degree of heat, was super- 
ficially calcined. Hence it is concluded that the Arragonite 
which accompanied it had undergone the same process, and 
parted also with a portion of its carbonic acid. Ón this ac- 
count, it is probable that the weight of water in 20 grains of the 
substance analysed cannot be far different from that which has 
been already stated, viz. 0.16 grain 
The 20 grains of Arragonite contained in the leaf of platinum 
were put into the bowl of a tobacco-pipe, which had a cover fitted 
to it, and exposed to a strong heat till the calcareous substance 
was thoroughly calcined. The lime weighed whilst warm 11.16 
grains: consequently the weight of the volatile matter driven off 
= 8.84 grains. But the weight of water in 20 grains of Arra- 
gonite = 0.16 grain. The weight, therefore, of the carbonic 
acid will — 8.68, or per cent. 
Grs. 
Lime - - = 55.80 
Carbonic acid - = 43.40 > = 100 grs. 
Water o. x — 0.80 
It does not seem, therefore, unreasonable to conclude that the 
water, since it appears to be an essential part of the composition 
of Arragonite, should produce that variation of specific gravity, 
hardness, and crystalline form, which distinguishes it from the 
common crystallized carbonates of lime. For though the quan- 
tity of water be not agreeable to the usual proportions in which 
bodies have been observed generally to unite; yet there are in- 
stances where great changes are produced by similarly small 
additions of a foreign ingredient. A very striking one, among ` 
many others which might be noticed, is in the change of iron to 
steel, which is effected by a quantity of carbon as small in pro- 
portion to the iron as that of the water in the Arragonite, 
Analyses 
