GYPSEOUS EARTH. 461 



the same effect was exhibited in specimens taken from the diggings, 

 and kept dry. The sulplmret 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, my friend 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 and 

 more general supply of gypsum already formed. 



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 the 

 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 fer- 

 tilizing 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 dig- 

 ging was sunk lower), that the work was suspended. But the 

 blacker earth above (D) and also the clay (J57) were carried out for 

 experiment on clover (May 26th), 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 the full benefit had been already seen on the first or spring 

 crop of clover) ; 100 bushels of the upper and better earth, or 150 

 of the clay, being applied to the acre. A good rain fell the next 

 night; and in less than ten days there were visible and manifest 

 beneficial effects from both kinds of earth, but better from the upper 

 which effects increased to fully the doubling of the growth by the 

 1st of August. The hard lumps of the compact clay soon split 

 and crumbled when exposed to the air, and even without rain. The 

 remarkable benefits of these applications induced the resuming of 

 the digging, and another and much deeper pit was dug as early as 

 the other labours of the farm permitted, and a statement will pre- 

 sently be made of the section thereby exposed. But previous to 

 this, it is proper to describe another like operation, and its results, 

 at a more interesting locality. 



The same general appearance of the gypseous earth, and mostly 

 of the poorer kind of greenish colour, mottled with pale yellow clay, 



* Now Professor of Geology and Agricultural Chemistry in the Univer- 

 sity of Alabama. 



39* 



