Points in the Composition of Soils. 143 



of the Peace River series, which is probably of the age of the 

 Niobrara group, and, of course, still more from the overlying 

 Laramie group. With regard to the latter, the author adduced 

 some new facts confirmatory of his previously expressed view as 

 to the position of the Laramie at the top of the Cretaceous and 

 base of the Eocene, and also tending to show that some of the 

 plants still held by some palaeo-botanists to be of Miocene age are 

 really, in Canada at least, fossils of the Laramie group, and 

 consequently considerably older than is currently supposed. These 

 facts also confirm the views previously expressed of the author as 

 to the Eocene or Laramie age of the fossil plants of Mackenzie 

 River and of Greenland, hitherto usually regarded as Miocene. 

 The collections of plants studied by the author had for the most 

 part been placed at his disposal by the Director of the Geological 

 Survey. 



IV. Some Points in the Composition of Soils; with 



Results Illustrating the Sources of Fertility 



of Manitoba Prairie Soils. 



By Sir J. B. Lawes, Bart., and J. H. Gilbert. 



This paper is a continuation of one given by the authors at 



the meeting of the American Association, held at Montreal in the 



autumn of 1882, entitled " Determinations of nitrogen in the 



soils of some of the experimental fields at Rothamsted and the 



bearing of the results on the question of the sources of the 



nitrogen of our crops. " 



The first part of the present paper consists of a resume of the 

 previous one. It was there shown that when crops are grown year 

 after year on the same land without nitrogenous manure, the 

 produce and the yield of nitrogen decline in a very marked degree. 

 This is the case even when a full mineral manure has been 

 applied ; and it is the case not only with cereals and with root 

 crops, but also with Legumincsse. Further, with this great decline 

 in the annual yield of nitrogen of these very various descriptions 

 of plant, when grown without artificial nitrogenous supply, there 

 is also a marked decline in the stock of nitrogen in the soil. 

 Tl us a soil-source of, at any rate, seme of the nitrogen of the 

 crops was indicated. Other evidence was also adduced clearly 

 pointing to the same conclusion. 



