308 SOURCE OF THIS FERTILISING ACTION. 



duce equal effects. This was explained by saying that 

 the less valuable beds did not contain so much potash 

 that they were coloured by chlorite, and not by the true 

 green grains ; second, that phosphate of lime, and espe 

 cially casts of fossils in phosphate of lime, similar to 

 those which our English green sands produce, were 

 known to occur in various places along the green sand 

 country in New Jersey j and, third, that the presence of 

 this mineral phosphate had never been suspected or 

 sought for in the green grains themselves, or in the 

 marly beds which occur in the green sand formation of 

 New Jersey. I regretted that my own leisure did not 

 admit of a personal examination of the localities the 

 importance of which these gentlemen readily acknow 

 ledged, when informed of what had been observed in 

 the green sands of England. 



I subsequently met, in Boston, with Professor Henry 

 Rogers, who was familiar with the geology of this New 

 Jersey country, and who was inclined also to rely upon the 

 potash of the green grains as the key to the good effects of 

 the sand, but whom the suggestion of the possible presence 

 of phosphate of lime at once satisfied of the economical 

 value and interest of the inquiry. He furnished me 

 with some varieties of the green grains and sand, in 

 which, upon analysis, I found from one to one and a-half 

 per cent of phosphate of lime, which, because unthought 

 of, had previously escaped the attention of American 

 analysts. But this result was valuable, chiefly as indi 

 cating the probability of larger proportions of this 

 mineral compound being found in other samples, and of 

 the possibility of further inquiry proving, as I expect it 

 will, that it was not the greater abundance of the green 

 grains, but of the mineral phosphate rather, which ren 

 dered one bed of sand more fertilising than another, and 

 that in some localities the phosphate might be found in 

 such abundance, as to pay for extracting it as a useful 



