240 FV. Hayden on the Geology of the Country 
occurring at the mouth of the Judith. The researches of Mr. 
H. Engelmann, in Utah, have also established the existence of an 
estuary deposit in the country bordering upon Green river,— 
scarcely less interesting than that of the Judith. These deposits 
pass up into the true lignite beds without any perceptible line 
of separation gradually losing their estuary character and ever 
after containing only land and freshwater shells. The lignite 
strata are chiefly remarkable for yielding in the greatest abun- 
dance, finely preserved vegetable remains. A few fragments of 
eaves of Dicotyledonous trees and silicified wood, with very im- 
pure lignite beds, are formed in some of the estuary-deposits but 
no groups to indicate the great luxuriance of vegetation which 
must have existed during the accumulation of the lignite 
Strata. : 
The geographical extension of the lignite deposits of the West 
is now a matter of the highest interest, and from what is already 
known, I am convinced that they will yet be found to cover a 
greater or less area on both sides of the main ‘divide’ of the 
Rocky Mountains, from the Arctic Sea to the Isthmus of Darien. 
The estuary and lignite beds seem also to have partaken equally 
with the older fossiliferous rocks, of the influence which elev 
the mountain chains. Along the Laramie mountains, and from 
the Laramie mountains, far to the northward, 
