31 



The crystalline appear to be various salts, well known to constitute 

 the most valuable portions of the manure. The mineral appear to be 

 sand. 



Frequently among Ichaboe-guano are to be found fragments of 

 bones belonging to birds : these appear to have undergone a remark- 

 able change, decomposition having in most cases destroyed the bony 

 matter, while the form of the bone has been preserved by a crystalline 

 substance, which forms a cast of the medullary canal. It would ap- 

 pear in many instances as if the bone had been converted into another 

 material, but I have satisfied myself that in all cases the bony matter 

 existed when the crystalline matter was deposited. If the crystalline 

 matter was only a displacement of the true .osseous substance, we 

 ought to have the medullary canal as in the perfect bone, which is 

 not the case, and which in the long bones of birds is extremely large. 

 The form of the osseous corpuscles when the bone exists externally 

 to the crystalline matter is precisely that of birds. 



Mr. Warington has examined the crystallized matter, and finds it 

 to be composed of sulphate of potash and ammonia. 



To account for the presence of such a salt, it will be necessary to 

 review the circumstances connected with the deposit of guano. All 

 are tolerably well acquainted with the fact, that certain sea-fowl in- 

 habit in myriads certain desolate islands in various parts of the world. 

 The excrements discharged by such numbers congregated in one lo- 

 cality must naturally, if not quickly decomposed, add a covering more 

 or less deep to the spot chosen as a place of resort by the birds. Let 

 it be imagined that one of these birds should die, when in a short 

 period its body would be entombed by its brethren, and decomposition 

 would naturally go on to a certain extent, the aqueous portions that 

 mingled with the solids would soon be evaporated in those dry cli- 

 mates, when the flesh would shrink and the bones lose the animal 

 matters from their interior, and if things remained so, a perfect mum- 

 my, as is often found, would be the result. But in other instances it 

 is to be supposed the dead carcass is buried in a damp situation, 

 when speedily the whole mass of flesh would decompose, and the 

 bones become infiltrated by water holding saline matters in solution, 

 which it obtains by percolating through the upper stratum of guano. 

 These saline matters entering the bones are disposed to crystallize 

 in their medullary cavities, and which are ultimately filled by the 

 compound previously mentioned. 



We must, however, retrace a step further, to determine from whence 

 comes the sulphate of potash (ammonia being readily engendered by 



