and from the North Coast of Scotland, 315 



the guano, supposing a period of dry weather to have preceded 

 its collection. 



It is worthy of remark, that both the Peruvian and African 

 guano, although abounding in nitrogenous compounds, are 

 destitute of nitric acid. This circumstance is strongly corro- 

 borative of the theory of the formation of nitre, in which car- 

 bonate of lime is held to be essential to the production of the 

 acid, by exerting a certain influence in uniting its gaseous 

 elements. 



The guano from the Pentland Firth was in firm lumps, of a 

 dirty brown colour, some of them speckled with white. It 

 had a peculiar smell, not unlike that of sea- weed, and unmixed 

 with any ammoniacal odour, till after having been triturated 

 moistened with lime, when it gave off a pretty strong smell of 

 ammonia, overpowering the odour first perceived. Broken up, 

 after soaking in water, when it offered no resistance, and care- 

 fully examined with the microscope, it was found to consist 

 chiefly of minute fragments of sea-shells and of sea- weed, with 

 which were intermixed a fine granular matter, and particles 

 of siliceous sand — leading to the inference that it was derived 

 from birds that feed mostly on sea-weed, and on the smaller 

 mollusca common amongst sea-weed. According to the infor- 

 mation with which I have been favoured by Professor Jame- 

 son, the birds inhabiting the Skerries are " cormorants, and 

 a few gulls and marrots." From a rough analysis, it appears 

 to consist of about — 



4 Matter soluble in water, chiefly muriate of ammonia, nitrate and 

 sulphate of lime, with a trace of common salt. 

 28 Matter destructible by fire, a mixture of vegetable and animal 



matter, nearly insoluble in wafer. 

 60 Matter not destructible by fire, consisting of 30.6 carbonate and 

 phosphate of lime, with a trace of magnesia, and a little sul- 

 phate of lime, and of 29.4 siliceous sand. 

 8 Hygrometric water, or adhering moisture. 



100 



Considering the proportion of carbonate and phosphate of 

 lime which this guano contains, as well as the saline matter 

 soluble in water, and the organic matter destructible by fire, 

 and capable of yielding carbonic acid during its slow decom- 

 position, it may be pronounced to be of some value as a ma- 



