22 



THE GEOLOGIST. 



layers to form strata, or round certain centres to form nodules, in a 

 manner analogous to that in which metals crystallize themselves from 

 their vast dispersion throughout the substance of the globe. It is 

 quite true, we know but little of the effects of such forces, exerted 

 incessantly during countless ages, but we have good reason to believe 

 that they have acted ; and may we not, with some probability, refer 

 to them such phenomena as I have described ? 



Let it be remembered, that two distinct facts demand explanation : 

 — 1st, the preponderance of lime in certain comparatively thin strata ; 

 and, 2ndly, the not less remarkable absence of lime in strata enor- 

 mously thick. Are not these facts correlative ? Is it not probable 

 that the lime which once composed part of the fossils in the earthy 

 strata has been agglomerated in these bands and nodules, by a process 

 on a large scale analogous to that which takes place in the formation 

 of flints, and, in some degree, like the aggregation of the metals ? 



Dear Sir, — I enclose the above suggestive note by my friend the 

 Rev. J. La Touche, a working geologist, trained in the the Ludlow 

 school. 



I cannot say I agree with him in his larger generalization, for there 

 is no doubt whatever of the actual deposit of these beds of limestone, 

 again and again, over the same area, with interruptions marked by the 

 deposit of shale. Nay, strange as it may seem, the beds of limestone, 

 crammed with fossils, often alternate closely with beds of shale, in 

 which one can hardly detect a fragment of a fossil. In these, and in 

 most cases, I believe, a band of limestone means — a period of " rest." 



The shale beds are signs of a 

 more turbid action of the 

 water. 



But then, his observation 

 is a good one for a great many 

 cases. No one who has stu- 

 died the old limestones can 

 believe they were deposited 

 "quite as we now find them — 

 full of strange lenticular 

 shapes, now crowding out the 

 shale beds, now completely 

 enveloped in them. Such 

 cases as the following are not 

 at all uncommon. 

 We may be well assured of two things : — 1. There was a bed 

 of limestone, for the nodules lie in horizontal planes, and are made 

 up of fossils in many cases. 2. The subsequent action has increased 

 the size of the limestone band, and given it a nodular form by at- 

 traction round central points. 



The old proverb, "He that hath shall have more," is, I believe, 

 strictly applicable in such cases. The band, comparatively rich in 



