Analysis of the CoproUtes of Birds. 47 



in dilute nitric acid. These are marks of uric acid. But on 

 concentrating the nitric sohuion, I failed to produce murexide. 

 Had the last been obtained, the evidence of the presence of uric 

 acid would have been decisive. The quantity I operated on 

 may have been too small to allow such a result to have been 

 observed. 



When we reflect that some specimens of guano contain less 

 than one per cent, of uric acid, we may well suppose that excre- 

 ments deposited, ages perhaps, before the oldest guano was evac- 

 uated, have undergone changes by which their urates have dis- 

 appeared. If this has been found in the sandstone of your bird 

 tracks, doubtless the consolidation of that has produced heat 

 enough to carbonize the urates in part; and this is probably the 

 source of the organic matter of the substance you sent for analy- 

 sis. This matter is insoluble in caustic potash, like insoluble 

 geine. If we are not allowed to consider the evidence of the 

 existence of urates decisive, still we may call this substance, 

 from its other characters, coprolite. I could detect a trace of 

 uric acid on treating it with caustic potash, after removing all 

 soluble salts by water and alcohol. 



The phosphoric acid was precipitated by lead, and its amount 

 determined from the phosphate of lead. There are traces of 

 alumina, which I suppose proceeded from the silicates, and I have 

 included its amount in those. 



[At my request. Dr. Dana sent me the following extract from 

 his laboratory note-book, detailing his experiments upon the cop- 

 rolite so far as the phosphates are concerned. — E. H.] 



Note-book No. 16, p. 42, Coprolite ? This is a sample pul- 

 verized, sent by Prof. Hitchcock. 



Sept. 7.— 1. 



2. Effervesces violently with muriatic acid, nearly all solves ; 

 a black powder remains. 



3. Gives off by heat a pungent smell, and a glass rod held 

 over it moistened with muriatic acid, shows white clouds, 

 (ammonia.) 



4. Rubbed up with caustic lime and treated with a drop of 

 potash, gave traces of clouds by muriatic acid. 



6. The muriatic solution (2) was precipitated by ammonia, 

 copious white gelatinous precipitate, which very slowly subsides. 



