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VI. — Remarks relating to the examination of Guano by the Micro- 

 scope. By Edwin J. Quekett, Esq., F.L.S., &c. 



(Read January 15, 1845). 



Having been induced by the constant adulteration of guano to seek 

 some means by which the genuine may be distinguished from the 

 adulterated, instead of the expensive and lengthened process of chemi- 

 cal analysis, I endeavoured to make use of the microscope for the 

 purpose of effecting this object. 



When viewed as an opaque object, guano appears to consist of 

 particles of an earthy brown colour, mixed with glittering bodies of 

 various sizes ; some of the latter being distinct from each other, and 

 appearing to be crystals and particles of sand ; others, however, are 

 collected more or less in bundles, and of needle-like character, and 

 which undoubtedly are crystals only. 



On examining various kinds of guano from different localities, it is 

 to be seen that the proportion of the crystalline to the brown amor- 

 phous particles is subject to much variety, insomuch so, that it is 

 quite possible to distinguish the Ichaboe guano from the Peruvian, by 

 the former having so many more bundles as well as single crystals 

 than the latter. 



My friend, Mr. C. G. White, has also noticed the fact of the varia- 

 tion of the proportion of crystalline matter in different specimens of 

 guano, and proposed the appearance to be a good guide for the col- 

 lection of it, when a microscope in the hands of the collector would 

 easily determine the valuable from the useless. 



Unfortunately, however, it does not appear that the specimens 

 which possess the greatest amount of crystalline matter are the best 

 in the market, as the Peruvian has less than the African, and beside, 

 the valuable matters of this compound are always flying away, and 

 many specimens, though exhibiting abundance of crystalline matter, 

 are nevertheless extremely inferior to others in which there is less, 

 on account of the virtues residing in greatest quantity in the amor- 

 phous earthy looking portions. 



Notwithstanding the microscope cannot determine accurately the 

 value of the different samples for the agriculturist, it is quite capable 

 of determining when the guano has been adulterated by foreign mat- 

 ters, on account of the different appearance it presents, as also in the 



