I 



as an Ingredient of Sea-Water. 323 



acid gas ; and the deposition, on the other hand, of carbonate 

 of lime, to perform the part of a cement on sand, converting 

 it into sandstone, in warm shallows, where the waves break 

 under circumstances, such as these are, favourable to the 

 disengagement of this gas ; and, I hardly need add, that the 

 same inferences will accord well with what may be supposed 

 to be the requirements of organization, in the instances of 

 all those living things inhabiting the sea, into the hard parts 

 of which carbonate of lime enters as an element. 



Apart from the economy of nature, the subject under con- 

 sideration is not without interest in another relation, — I 

 allude to steam navigation. The boilers of sea-going steam- 

 vessels are liable to suffer from an incrustation of solid 

 matters firmly adhering, and with difficulty detached, liable 

 to be formed on their inside, owing to a deposition which 

 takes place from the salt water used for the production of 

 steam. On one occasion that I examined a portion of such 

 an incrustation taken from the boiler of the " Conway," a 

 vessel belonging to the West Indian Steam-Packet Com- 

 pany, I found it to consist principally of sulphate of lime, 

 and to contain a small proportion only of carbonate of lime. 

 This vessel had been employed previously in transatlantic 

 voyages, and also in intercolonial ones, plying between Ber- 

 mudas and the island of St Thomas, and in the Caribbean 

 Sea and the Gulf of Mexico. 



The composition of this incrustation, like the preceding 

 results, would seem to denote, if any satisfactory inference 

 may be drawn from it, that carbonate of lime is in small 

 proportion in deep water distant from the land, and that 

 sulphate of lime is commonly more abundant. The results 

 of a few trials I have made, whilst rather confirmatory of 

 this conclusion, shewed marked differences as to the propor- 

 tion of sulphate of lime in sea-water in diff'erent situations. 

 That from Carlisle Bay was found to contain 11-3 per 10,000. 

 A specimen taken up in lat. 29° 19', and long. 50'-45, yielded 

 about 2 per 10,000, with a trace of carbonate of lime. A 

 specimen taken up off Fayal yielded about 9 per 10,000, also 

 with a trace of carbonate of lime. One taken up off Port- 



