OCR Text |
Show ACTION JN DEEP WATER. HlLL-MAKING UNDER WATER. That hypothesis is not o~tly in .stri?~ accordance with the whole of nature,. rn all 1ts kmgdoms, and in all the-ir p·roduction~ and phen_omena, but it e~plains many things whwh otherwise are puzzles m geology; and it enables even t.ho~e whose means and opportunities· are the most hm1ted to turn even the progre~ of the most common labo~r i.nto a means of instruction and pleasure. The d1ggmg of a quarry, or even the cutting of a drain, may be made a study of nature, and the hand t~at works may work with more ardour and success m consequence of there being instruction, and consequently pleasure, in the working. The coal mines, from the extent and depth to which they have been worked, are perhaps the t;>est places for observing the traces of that workmg. The coal itself has been vegetable matter, for the~a are vegetable impressio.ns in it. It lies generally m basins, and there are m most cases many se:Ims,. and some of them deep below others, so that the "coal measures," or strata in which the coal is found, have been formed gradually. They consist chiefly of limestone clay, iron stone) and sandstone, COAL FlELDS. 251 the accumulation of which must have required a long period of years. But they also show traces of volc'anic action, in the "dikes and cutters," by which they Hre intersected, and which often throw the strata out. of the plane, so that the coal is higher on one side of the dike than on the other. Thobe dikes are frequently "whinstone," or allied to basalt ; and there are cases in which the basalt has issued in quantity and formed '' caps" on the top of the other strata. The coal-field in the south of Fifeshire is remarkable for those caps, which there form very beautiful conical hills, locally termed "laws." The top of one of these, "Kcllie law," is, under the green sod, as regular a basaltic pavement as the top of Staffa. We may, by the observation of what we see going on at the surface of the earth, understand how a bed of sand, clay, or gravel is formed; and there are instances in abundance of the formation of peatbogs. In those cases we can also in general tell whether the bed has been formed in a pool, or by ~n occasional fall of rain, or flood. But when we look at even a very limited portion of the tamest country, we are utterly unable, by any power of which we can see or imagine the working in t.he air, to account for the form of its surface. The gravel and clay hills, near London, again occur as the m?st familiar instances, though they are far from bemg the most striking ones. Water, whether of the sea or not, must at all times have preserved its level, because that is the very constitution of its nature, and with'Out that it could not have been water. The currents ·of the sea may have done a little, but it couiJ.d be only a little; for it does not appear that even the Gulf-stream of America rolls stones before :t; and the little coral insects are quite competent to the task of erecting a wall from the unfathomable depths, sufficient to stay the roll of the wide Pacific, even in its most storm~ latitude, and with a tide. |