AMERICAN INSTITUTE. 325 



Soluble phosphates, 33 per cent. 



Phosphate soda, &c., 5 do 



Sand, - - - 4 do 



This Island is about six miles broad, with a deposit thirty feet 

 deep. A cargo of 1,000 tons is now on the way here. The quan- 

 tity calculated on the Island is over 2,000,000 tons. 



BAKER'S ISLAND GUANO. 

 Dr. Deck gave his opinion very favorable to the guano from 

 Baker's Island. He said guanos are of two kinds. One contains 

 an excess of ammonia, and the other an excess of phosphates. 

 One is more suitable to one soil or crop than the other. The 

 phosphate guano is a more durable fertilizer than the other. 

 Sometimes its effects last for years, and therefore more adapted to 

 the permanent improvement of land. Some statements of experi- 

 ments made with Baker's Island guano, which contains a large 

 per cent of phosphates, show it a more valuable fertilizer than 

 Peruvian guano. 



Professor James J. Mapes inquired, and found that this guano 

 "was identical with what had been imported into Boston as Mexi- 

 can guano. It was not hard to grind it. 



Before the subject of the day was taken up. Prof. Mapes was 

 anxious to speak of phosphate of lime. He only repeated what 

 he had so often reiterated as to the specific difference in the mate- 

 rial, and the results of the native mineral and that which has 

 passed through living organisms. The phosphate rock will not 

 assimilate with plants, nor act as a pabulum. He did not believe 

 that the dung of birds was the foundation of the guano so abun- 

 dantly brought here. It was notorious that the mineral matter 

 derivable from a burnt haystack was tar more valuable than the 

 same quantity of the same mineral matter taken from the rock. 

 Analytically alike, the practical value w^as quite another thing. 

 It was an important fact and could not be too extensively known. 



Dr. Deck said that these injurious results of the native mineral 

 are, perhaps, traceable in the aj^atite of Estemadm-a, and in other 

 cases, owing to the presence of fluoride of calcium, which is poi- 

 sonous to plants. 



