Analysis of the Coprolites of Birds. 69 



remain, no trace of which was found in your coprolite. It seems 

 not very probable that this salt should have been wholly re- 

 moved as a soluble urate, while more soluble salts, chlorides 

 and sulphates, have remained. Let it be supposed that your cop- 

 rolite has been dropped by a purely carnivorous bird. The uric 

 acid here exists as a urate or muriate of ammonia. If all this is 

 removed, we have left only phosphate of lime, wholly unlike 

 your coprolite. There are therefore two considerations which 

 will not allow us to class that substance with the droppings of 

 reptiles, or of purely carnivorous birds. The first is founded 

 on their chemical composition ; the second is founded on the 

 great improbability of such droppings having been- so placed as 

 to allow the almost complete disappearance of even the urate of 

 ammonia, The most probable supposition, had that been the 

 case, would be, that your coprolite was dropped by an alligator, 

 the urine of that animal, according to Davy, containing the larg- 

 est proportion of phosphate and carbonate of lime. 



It is not probable that your coprolite has been more favorably 

 placed than guano, for the removal of its uric acid and urates. 

 If now we look at the composition of guano, no substance claim- 

 ing a common origin varies more in its composition. From 

 Klaproth, who first analyzed it, to Bartels, whose analysis is the 

 last I have seen, we find that guano presents a mass of birds' 

 droppings in various states of decomposition, and various salts, 

 the result of that process. If we compare your coprolite with 

 the results of Prof Johnston's examination, it will appear to 

 have undergone in its uric acid, not far from a similar amount 

 of change, and a more perfect removal of its urates and soluble 

 salts. The small portion of uric acid found by Prof J. has a 

 direct bearing on this question. That even guano is not the 

 product of birds feeding only on fish, is evident from a compari- 

 son of its composition with that of the droppings of the sea 

 eagle. No decomposition of that would afford the results pre- 

 sented by guano. Let us tabulate the results of the analysis of 

 that substance.* 



* For more recent analyses of guano, see the subsequent pages of this volume, 

 where the results of Mr. E, F. Teschemacher and Mr. Dunham Smith will be 

 given. — Eds. , 



