191 



that it consisted chiefly of humus and the acids of the crenic 

 group. 



From this analysis I thought myself justified in announcing that 

 the lime and magnesia in the compound under consideration are com- 

 bined with the phosphoric acid so as to form a tribasic salt, in which 

 one atom of water substitutes one atom of alkaline earth, according 

 to the formula 2 MO, HO, PO.. A subsequent examination and recal- 

 culation of my results has convinced me that the announcement was 

 somewhat premature, and that the analysis would not fully bear the 

 construction put upon it. I have, however, never changed the opinion 

 then advanced, as the discrepancies are slight and easily accounted 

 for. 



The statement of my views led to further investigation. Among 

 others, Dr. Campbell Morfit examined the substance, and came to 

 a different conclusion from that at which I had arrived. Drs. Hig- 

 gins and Bickell, Chief and Assistant State Chemists of Maryland, 

 shortly after published a paper in which they agreed with me in the 

 main. Their analysis was more elaborate than mine, and comprised 

 two distinct examinations; one of the white, poUshed crust, the other 

 of the body of the rock. Without going into minutia, I will simply 

 state that they found the exterior layer to contain phosphates of 

 lime and magnesia, of the formula 3 MO PO^ while, in the body of 

 the rock, the salts were composed, as I had previously announced. 

 They also ascertained that in the outer layer the sulphuric acid was 

 combined with soda, while in the body of the rock it was united to 

 lime. 



A discussion ensued upon the application and effect of sun- 

 dry articles used as manures, and their influence upon different 

 soils and crops, — in which Dr. Dunglison, Prof. Frazer, Dr. 

 F. Bache and iVIr. Trego participated. 



Stated Meeting, May 16. 



Present, sixteen members. 



Prof. Frazer, Vice-President, in the Chair. 



Dr. S. L. Hollingsworth, a recently elected member, was 

 introduced and took his seat. 



VOL. VI. — 2 D 



