GYPSEOUS MARL. 145 



sifoly may have some influence on the operation of the substance, 

 as manure or cement. 



Thus, from the examination of a single body of marl, there have 

 been obtained not only a rich calcareous manure, but also gypsum, 

 and a valuable cement. Similar formations may perhaps be 

 abundant elsewhere, and their value unsuspected, and likely to re- 

 main useless. This particular body of marl has no outward ap- 

 pearance of possessing even its calcareous character. It would be 

 considered, on slight inspection, as a mass of gritty clay, of no 

 worth whatever. 



[The last preceding paragraphs present, as in the previous edi- 

 tions, my earliest views of this particular bed of marl. Further 

 information has taught that it is of the eocene, or more ancient 

 formation ; and that the underlying stratum (which is usually not 

 at all calcareous), which I formerly named and treated of as " gyp- 

 seous earth," is what geologists call t( green-sand/' a term still less 

 descriptive, and not at all more accurate. A full account of both 

 of these bodies will be given in the Appendix. 1842.] 



This gypseous marl has been used only on sixty acres, most of 

 which was neutral soil, and generally, if not universally, with 

 early as well as permanent benefits. The following experiments 

 show results more striking than have been usually obtained ; but 

 all agree in their general character. 



Experiment 18. 



1819. Across the shelly island numbered 3 in the examinations 

 of soils (page 60), but where the land was less calcareous, a strip 

 of three-quarters of an acre was covered with mussel-shell marl, a 

 deposit on parts of the river banks supposed to have been made by 

 the aboriginal inhabitants. Adjoining this, through its whole 

 length, another strip was covered with gypseous marl, 53 per cent., 

 at the rate of 250 bushels. 



Results. 1819. In corn. No" perceptible effect from the mussel- 

 shells. The gypseous marling considerably better than on either 

 side of it. 



1820. Wheat less difference. 



1821. Grazed. Natural growth of white clover thickly set on 

 the gypseous marling, much thinner on the mussel-shells, and still 

 less of it where no marl had been applied. 



The whole field afterwards was put in wheat on summer fallow 

 every second year, and grazed closely the intervening year : a 

 course very unfavourable for observing, or permitting to take place, 

 any effects of gypsum. Nothing more was noted of this experi- 

 ment until 1825, when cattle were not turned in until the clover 

 reached its full size. The strip covered with gypseous marl 

 showed a remarkable superiority over the other marled piece, as 

 13 



