6 ' Introductory Views. 



gradually" produced, is certain from the nearly horizontal position of 

 the rocky strata, so far as they have fallen under our observation ; 

 and it is also certain that it was preceded and accompanied by 

 the occasional subsidence, or sinking, or occasional flooding of 

 lands, probably islands, abounding with tropical plants, and trees, 

 which were deposited in the coal measures of the valley. There 

 is a degree of probability, little short of certainty, that these trees 

 and plants grew on, or near the spot where their remains are now 

 found,, for they are universally in a horizontal position, as if laid 

 tranquilly down by water ; in general, their delicate forms are perfect- 

 ly preserved, indicating gentle deposition, and when they are mixed 

 together in confusion, it of course implies a correspondent agitation 

 of the water. That they are the growth and deposit of remote pe- 

 riods of time, is inferred from the specific difference of many of the 

 fossil plants, in the different beds, compared with those of modern 

 times, and from the vast deposits of sand and clay, which separate 

 them ; these are frequently not less than one and two hundred feet 

 in thickness, as will be more fully shown in the sections of strata, 

 at different places. It is the opinion of most geologists of this age, that 

 the tropical plants, found in the coal beds, grew either on, or very 

 near the spot where they are now inhumed ; and that the climates 

 which produced such plants, have been changed by the gradual al- 

 terations which have taken place on the surface of the earth by the 

 changing of oceans into dry land ; the same latitudes covered with, 

 or surrounded by water, being from the known capacity of water to 

 retain and equalize caloric, much warmer while in this condition, than 

 after becoming dry land. Some attribute the greater warmth of the 

 'earth in the higher latitudes in the earlier periods, to the greater inter- 

 nal heat, which is supposed to have gradually declined. The depos- 

 its of sand, clay, &;c. over the coal, and in alternation with it, must 

 have been produced by aqueous agency in some form, either in 

 lakes, or in bays, estuaries or lagoons of the ocean, or in gently flow- 

 ing waters. Mr. Parkinson in his " Introduction to the study of 

 Organic Remains," makes the following remarks. " By these 

 facts we learn that at some remote period of the existence of this 

 planet, it must have abounded with plants of the succulent kind, and 

 as it appears from their remains in great variety of form and luxuri- 

 ancy of size. These, from what is discoverable of their structure, 

 were beset with seta and spines ; were not formed for the food of 

 animals, nor from the nature of the substance of which they were 

 composed, were they fitted to be applied to the various purposes to 



