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The export guano is sold in accordance with the analysis of the guano 

 which considers moisture, sand and silica, nitrogen and phosphoric 

 acid This has led to the establishment of laboratories on the principal 

 guano Islands. If a class of guano is not up to the standard, it is reject- 

 ed or used as a reducer for guanos of extremely high grade. The 

 guano for home use is often purchased without any definite agree- 

 ment as to quality; but some of the estates that have laboratories 

 demand a guano of a more or less certain analysis. By long years of 

 practice, the contractors who gather the guano are able to distinguish 

 different qualities without the aid of a chemist. They fit themselves 

 out with a schooner and go from Island to Island until they have a 

 cargo. Some estates have secured as high as 2,500 tons per annum. 



