2? 



different localities as illustrated by chemical examination. A large 

 proportion of the matter of all shells consists of carbonate of lime. 

 Hence they are nearly identical in composition with limestone, chalk 

 and marble. To this ingredient, in whatever form it may be applied 

 to the soil, general experience has ascribed a very high degree of fer- 

 tilizing power, and hence, in the application of all the varieties of cal- 

 careous marl, we are guided chiefly by the proportion of the carbo- 

 nate which they contain, as determined by chemical analysis. It 

 should not, however, be inferred, that the various mixtures of earths 

 and other substances with which the calcareous matter is usually as- 

 sociated, are devoid of useful action when applied to land. The ex- 

 perience of agriculturists is certainly inconsistent with such an opi- 

 nion, though it has most clearly evinced the powerful efficacy of cal- 

 careous manures. The invaluable publications of the editor of the 

 Farmer's Register by directing the attention of farmers to the em- 

 ployment of the shell marl with which nature has supplied them in 

 such rich abundance, have led so extensively to the application of 

 this manure, and have produced so general a conviction of its fer- 

 tilizing effects as to render it unnecessary in this place to introduce 

 either facts or arguments in its favour. To the valuable practical 

 suggestions of this gentleman, contained in the " calcareous manures" 

 and other publications, we are indebted for much of the amelioration 

 which has taken place in the agriculture of eastern Virginia, and I 

 therefore cannot do better, in alluding to this branch of my subject, 

 than to recommend these works to the earnest perusal of all who are 

 interested in advancing the prosperity of that portion of the state. 



But although the richness of the marl is mainly dependent on the 

 proportion of its calcareous contents, it is also largely influenced by 

 the nature and condition of the shells of which it is composed. It is 

 well known that the recent oyster shell, especially in its unbroken 

 state, is far less immediate and powerful in its action upon land than 

 the friable and pulverulent shells, of which many of the most valua- 

 ble marl beds are principally made up. Yet in the composition of 

 the recent oyster shell, the amount of calcareous ingredient is nearly 

 as great as in the richest marl beds which we have examined. Ac- 

 cording to an analysis which I made some years ago, 100 grains of 

 this material were found to contain : 



