L. oe on the Coal Formations of North America, 25 
shila of the cena? seas; with sandstone Non without any 
ossil remains: this alternation evidently shows that at the time 
when the formation was progressing, the sea was continually 
brought in contact with the coal and covered it most of the 
time. Hence it follows; that if the coal has been formed in 
marshes like our peat bogs, we ought necessarily to admit of a 
submergence and therefore of a subsidence of the land after 
each dep osit of woody matter, and of an upheaval of the same 
land to bring it up again above the level of the sea for each 
successive growth of a new peat bog. This appears to some 
geologists an unaccountable and unnecessary use of nature’s 
internal forces; a kind of lusus nature, resembling a miracle. 
To meet this objection, they have supposed that the peat bogs of 
the coal measures grew on the deltas of some large river, “and 
neeneees exposed to periodical inundations: that as fast as the 
peat grew, the river brought upon it mud and sand, the ma- 
= toa which the shales and the strata of sandstone were 
orme 
course of time, built upon them. ition strata of limestone: that as 
soon as these strata reached the surface of the sea (a fact which 
probably supposes that the —— of pa re had stopped - 
for a while) the land plants began to appear again, the peat to 
grow, and the matter to be heaped up till anothes large periodical 
— of the river brought new deposits of mud and sand; 
thus by continuous subsidence and repeated inundations, 
the coal, shales, sandstone and limestone strata were alternately 
orme 
Before tsa any reasons in support of the alternation of up- 
pero an 
nai extent of a basin, or in =a words, «that each sinetetties is 
generally horizontally ectended over the whole coal-field in a continu- 
ous sheet, so that each seam is accompanied by the same strata rr 
and below.” This is only partly true. In the coal-fields of the 
United States, it is true only of some beds of coal and of one 
or two strata above the conglomerates. Every practical geolo- 
gist knows well that it is impossible to gg the peaitiees of a 
bed of coal by means of its. adjoining strata. If the same stra 
SECOND SERIES, Vot. XXVIII, No. 82.—JULY, 1869. 
4 
. 
