WILLIAM B. DWIGHT. 99 
when he comes to make a report of his work. Whatever 
nomenclature he adopts is sure to meet with adverse 
criticism from many geologists. 
This confusion has had two chief points of origin ; one 
in Europe, one in America. The trouble in Europe arose 
primarily out of the excellent and honest, yet partially 
conflicting work of the two great field-workers on English 
strata—Sedgwick and Murchison. A fair account of 
II 4% 
this is given in Geikie’s ‘‘ Text Book of Geology. 
Mr. Murchison began in 1831 the study of the Sub- 
Devonian fossiliferous strata, which, as a whole, he desig- 
nated Silurian ; these he subsequently subdivided into 
Upper and Lower Silurian, with the dividing line be- 
tween the unconformable Upper and Lower Llandovery 
groups. In continuing his researches through a long 
period of years, he gradually extended the Lower Silu- 
rian downward by new finds of fossils until he made it 
to embrace all the lower strata which were characterized 
by a ‘‘trilobitic and brachiopodous fauna.’’ This was, 
in fact, claiming under his title all the lower strata 
_ known to be fossiliferous ; for all the strata presumably 
of sedimentary origin which were lower were considered 
and described as ‘‘barren slates and grits.”’ It should 
here be noted that Murchison was preéminently a paleon- 
tologist, and was guided in his stratigraphic conclusions 
primarily by the character of the fossils collected. 
His work was carried on chiefly along the borders of 
England and Wales. 
Meanwhile, Sedgwick, with no less zeal, beginning at 
the other and lowest end of the problem, had been carry- 
ing on his work in Wales. The lowest and barren schists 
and grits of Wales he called Cambrian. So far, there 
was as yet no conflict with the Silurian of Murchison. 
But he soon extended his researches and the title 
* Second Edition, 1885, page 650. 
49 
