398 MANIPULATION. 



the same way. The guano, from containing a large amount 

 of animal matter, requires a rather diflferent mode of 

 treatment. Mr. Henry Deane, of Clapham, who has paid 

 considerable attention to these matters, has recommended 

 the following as the best method of proceeding :* — " Take 

 any convenient quantity of pure Ichaboe guano, and wash it 

 by repeated ablutions of distilled water, until the water is no 

 longer coloured, observing, after each addition of water, that 

 it must be well stirred two or three times, and then allowed 

 to settle for some hours. When sufficiently washed, a small 

 quantity of hydrochloric acid is to be added to the water last 

 used : this dissolves some portion of it with effervescence, and 

 causes a more perfect subsidence of that portion which it does 

 not act upon. After this, allow sufficient time for the deposit 

 to become well settled down ; then, the clear liquor being 

 poured off as clearly as possible without loss of the sediment, 

 a quantity of strong nitric acid, in the proportion of about 

 two fluid ounces to every ounce by weight of guano employed, 

 is to be added. A strong effervescence takes place, which is 

 to be assisted by setting the mixture in a warm place, at the 

 temperature of about 200°, for six hours, during which time 

 the greater part of the guano is dissolved. After allowing it 

 to stand in a cold place for twenty-four hours, pour off the 

 acid liquor as closely as possible, and wash the sediment with 

 an abundance of distilled water. The finer portions of this 

 sediment will contain all the siliceous shells of the guano, 

 perfectly freed from extraneous matter." It should be borne 

 in mind, in aU these cases, that some time should elapse before 

 the acids or the distilled water are poured off from the 

 sediment, in order that the solid matters may subside, 

 as it has often happened that the most beautiful of the 

 infusoria have been thrown away with the water employed to 

 wash them. 



* Transactions of the Microscopical Society, vol. ii. 



