178 W. J. Taylor on Rock Guano. 



tinctly marked, and it resembles to a certain extent in its appear- 

 ance the menilite of Menil Montant near Paris; the concentric 

 layers composing it are well marked, and when they are frac- 

 tured or cut across, an appearance is presented not unlike some 

 varieties of agate. 



The following is the result of an analysis : 



2*0266 grammes ignited lost 0-1640 grammes gave 13-03 p. c. 



u a 



« it 



Ag 0-0274 " chlorine 0*44 " 



CaO, SOa 0-0419 " siilphuric acid 1-93 " 





41 U 



X 



CaO, SOs 1-9965 « lime 4064 



2MgO, P05 0-1654 « magnesia 2-93 



2Mg:0, P05 I'lTSS « phosphoric acid 3 MS 



« « residue 0-0111 " residue 0-55 



" " NaCl 0-1231 « soda 3-23 



Loss by ignition, 13-03 per cent. Oxygen ratio, 



Chlorine, 0-44 



Sulphuric acid, 1-93 « " " I'lS 



Phosphoric acid, 37-] 5 " « " 20-82 



Lime, 40-64 " « " 11 '55 



Magnesia, 2'93 ** " " I'lT 



Soda, 3-23 " » " 0-82 



From the oxygen ratio of this it appears that the phosphoric 

 acid and lime exist in the proportion of 3CaO, PO5. The cruci- 

 ble after ignition showed indications that chlorid of iron had 

 been volatilized. 



Below this exterior crust the rock has a varied appearance ; it 

 is of a dark brown color, in places quite black, and varying in 

 others to a lighter shade, in which portion are frequent cavities 

 filled with minute crystals of gypsum, readily recog-nizable with 

 a pocket lens. The darkest portion is the most solid, with a 

 slightly vitreous lustre, and of a much greater density and hard- 

 ness than any other portion of the guano ; it has a sub-conchoidal 

 fracture, sometimes splitting into thin fragments which are trans- 

 lucent ] through some portions of it I have frequently observed 

 thin irregular bands, -^^d to j^*6 th of an inch in width, which have 

 the appearance of carbon. 



This portion was selected for analysis with particular care, 

 with the view^ to ascertain its exact composition ; it was with 

 difficulty reduced to the finest powder and treated with distilled 

 water (m the cold) in a beaker glass, being frequently stirred 

 for several days in order that the water should be in frecjuent 

 contact with the particles; it was then collected on a weighed 

 filter and washed with cold water until the filtrate showed no 

 trace of sulphuric acid ; the excess of filtrate was evaporated to 

 dryness, and a thorough analysis made of it, the result of w^hich 

 is the foilowdng; 



