CALCAREOUS MANURES— APPENDIX. 215 



excited in regard to this manure. The quantity applied was generally 40 

 bushels of the earth to the acre. And this quantity seemed, (from an accu- 

 rate comparative experiment) to produce as much benefit as 200 bushels. 

 The growth of clover was increased in degrees varying from 100 to 300 

 per cent. And where the application was most successful, the increase and 

 profit were sufficient to compensate the expense, even though no further 

 benefit shall be found than in this one crop— or that a new application shall 

 be required and be made for every succeeding crop of clover, or once in 

 each round of the rotation of crops. 



An observation made by accident last spring led to further chemical as 

 well as other examinations of this earth, and to important results. Upon 

 heating a lump of it to red heat, I found that strong fumes were thereby 

 extricated, which were almost suffocating if inhaled incautiously. The 

 odor was manifestly sulphureous in part, and principally ; but it seemed 

 not altogether so, but to be mixed with some other, much like that of mu- 

 riatic acid gas. Similar trials were made on many specimens, and all the 

 darker and (as supposed) richer layers of the green earth at Coggins Point 

 showed the like result. From specimens of the upper and lighter green 

 stratum (C) when heated red, there was nothing of this suffocating odor 

 produced. And it may be useful to state here, in anticipation of subjects to 

 be hereafter more fully considered, that I subsequently found that the New 

 Jersey green-sand earths yielded not a particle of this gaseous product. 



This odor, so far as it was sulphureous, was obviously the product of 

 the decomposition (by red heat)of sulphuret of iron — which was thus proved 

 to be universally diffused, though invisible, through all the darker and bet- 

 ter kinds of this earth. Sulphur would have shown like results, with a 

 much less degree of heat ; but it cotild not be that, because the heat suffi- 

 cient to decompose sulphur (and to evolve its fumes) had no effect on the 

 earth. I also observed that lumps of the earth after having been applied as 

 manure, and exposed on the surface of the ground for some months, often 

 had a smell of sulphur; and, in some cases, the same effect was exhibited 

 in specimens taken from the diggings, and kept dry. The sulphuret of 

 iron, if universally present, would, by its decomposition in contact with 

 carbonate of lime, (as when on calcareous land,) form sulphate of lime, 

 (gypsum.) This showed a source for the universal supply of that manure 

 to some extent. Further, Mr. M. Tuomey had found sulphate of lime 

 ready formed in specimens of wet earth which I supposed the least likely to 

 retain that ingredient — and thus was indicated another general supply of 

 gypsum. 



The increased interest excited by these new observations, and also the 

 new views as to the cause of the failures of most of the former applications 

 of this manure, induced the sinking of a pit in the gypseous earth, on the 

 river beach at Coggins Point, to the depth of 18 feet below ordinary high 

 tide. This digging for tlie lower 13 feet was in a very compact and fine 

 clay (E) or clay marl, as it would have been designated in England, from its 

 texture and sensible qualities, but which contained no visible or apparent 

 fertilizing ingredient, except a very small sprinkling of shells, and elsewhere 

 some little sulphuret of iron in small lumps and in minute crystals, visible 

 in a few detached spots only. The appearances promised so little of value 

 or remuneration, (and less so as the digging was sunk lower,) that the 

 work was suspended. But the blacker earth above (D) and also the clay 

 {E) were carried out for experiment on clover, (May 2Gth,) of which the 

 first crop had just been grazed off closely, and the cattle removed. As the 

 season was so far advanced, and benefit so little counted on, the covering 

 was made heavier than in the winter and early spring before (and of which 



