346 SOURCES OF THE PHOSPHATES. 



The specimen of laconic slates belonging to New-York, not proving so rich in phosphates 

 as that from Maine, I made an examination of another specimen, which was softer, as No. 

 3 had proved more siliceous than was anticipated. Hence I selected a soft variety, which 

 occurs in a compact slate at Salem, and which is extensively used for the foundation of 

 buildings. As my object principally was to ascertain the constancy of the phosphates in 

 these slates. I proceeded no farther than was necessary to test, in a satisfactory manner, 

 this question. A solution, therefore, of 100 grains was made, after thorough boiling in 

 chlorohydric acid; the solution was freed from silica, and the alumina, iron, etc. with the 

 phosphates precipitated. The last precipitate was again dissolved, and exactly neutralized 

 by caustic ammonia ; when acetate of potash threw down, in a short time, a large quantity 

 of the phosphates. From this examination, it appears that the phosphates are commonly 

 present in these slates, and greater in amount in the softer than in the harder and more 

 siliceous ones. 



It will be observed that the roofing slate of Hoosic contains epiite a large percentage of 

 potash. This potash may be in a larger quantity in the fucoidal slate, than in those which 

 are destitute of the marine productions. 



From the foregoing observation^, we are furnished with a clue to the source of the im- 

 portant elements, potash, and the phosphate of alumina, iron and lime, which are so 

 frequently contained in the soils of the Eastern or Taconic district. 



We may dow proceed to slate the refill's which we have obtained by a special examina- 

 tion of the softer shales and slates situated geologically above the Tully limestone. I 

 selected, for this examination, a specimen of slate from a quarry south of Cortlandville. 

 It was greenish, and contained the fossils which characterize the Ithaca group, or the lower 

 part of the Chemung group. 



ana: 



"Water 3-03 



Silicates 83-50 



Peroxide of iron and alumina 12-56 



Carbonate of lime 0-61 



Magnesia 0-30 



100-00 



Phosphates appreciable in 100 grs. Potash was not obtained. The presence of 

 phosphates was clear and distinct. 



From this examination, we find an explanation of the fact why indian corn is a better 

 crop upon those lands situated above the Onondaga-salt group, than it is below or imme- 

 diately upon this series, inasmuch as it has been shown that the Onondaga-salt group is 

 comparatively destitute of the phosphates. 



Where fossil remains are abundant, we may always expect to find phosphates. In the 

 above analysis, we selected a piece which was destitute of organic bodies ; and it seems 



