270 ANNUAL OP SCIENTIFIC DISCOVERY. 



change and fermentation in other moist substances with which it is mixed 

 or is brought into contact. It acts after the same manner as sour leaven 

 does when mixed with sweet dough. 



Now, old and partially decayed cheese acts in a similar way when intro- 

 duced into the stomach. It causes chemical changes gradually tp com- 

 mence among the particles of food which has previously been eaten, and 

 thus facilitates the dissolution which necessarily precedes digestion. It is 

 only some kinds of cheese, however, which will effect this purpose. 

 Those are generally considered the best in which some kind of cheese 

 mould has established itself. Hence the mere eating of a morsel of 

 cheese after dinner does not necessarily promote digestion. If too new, 

 or of improper quality, it will only add to the quantity of food with 

 which the stomach is already overloaded, and will have to await its turn 

 for digestion by the ordinary process. Chemistry of Common Life. 



GUANO. 



At a meeting of the Society of Arts, some interesting statistics relative to 

 guano were presented by Mr. Horace Green. 



Guano is generally understood to have been brought to the notice of 

 ~"uropeans by Humboldt in 1804. It was first brought to England as 

 merchandise in 1839. It had, however, been used in Peru for 600 years. 

 Of this excrementitious matter voided by sea-birds, a very large proportion 

 was decomposed before the guano of commerce was extracted from its 

 beds, and more still before its arrival in port. Proof of the rapid depre- 

 ciation of guano in keeping might be found in the analyses of the dung 

 of birds by Sir Humphrey Davy and M. Coindet. Coindet found in re- 

 cent excrement 8.61 of pure ammonia, and of ammonia in the form of its 

 equivalent of uric acid 35.20, making a total of 43.81 percent. Davy 

 found that the soluble matter of the dung of pigeons decreased from 23 

 per cent, in the recent excrement to 16 per cent, in that of six months 

 old, and to eight per cent, after fermentation. It appeared that in five 

 years (1845-50) nearly 650,000 tons of guano had been brought almost 

 round the world for the stimulation of the soils of this country ; but it 

 was generally believed that the zenith of supply from Peru was past. 

 From the mean of many analyses of different varieties, it was stated that 

 the amount of ammonia was, in Saldanha Bay, 1.68 per cent. ; in Pata- 

 gonia, 2.55 per cent. ; in Cape and Algoa Bay, 2.00 per cent. ; and in the 

 New Islands, 1.96 per cent. ; but in phosphate of lime, which was the 

 next most important element, the guanos were richer as they were poorer 

 in ammonia. The mean amount of phosphate of lime was, in Saldanha 

 Bay, 55.40 per cent. ; in Patagonia, 44.00 per cent. ; in Cape and Algoa 

 Bay, 20.00 per cent. ; and in the New Islands, 62.80. The question, 

 however, arose, whether or not large quantities of such manures could be 

 sold at a price which should not exceed the home cost of super -phosphate 

 of lime. Keference was then made to the Guano Substitute Prize of 



