443 



THE GEOLOGIST. 



witlithe fine material, being heavy and difficult of transport, will drop down nearly 

 at the points where they lie, and remain scattered along the margin of the lake. 



" If, now, the lake be frozen, the expansive force of the ice pushes up everything 

 moveable near the shore, and forms a ridge at the uppermost limit reached by the 

 congealed water in expanding. This ridge will consist mainly of boulders covered 

 by and mixed with sand, gravel, and the exuvia) of the shore. When the ice melt s, 

 everything but the boulders is soon washed away on the side of the ridge towards 

 the lake ; and the boulders are there exposed, forming a rough wall. Subsequent 

 congelation crowd the boulders closer together against the bank or ridge, and 

 render the wall more perfect. In this manner the lakes of Wisconsin, Iowa, and 

 Minnesota have often become girt with walls having a very artificial character, 

 properly referable to physical laws operating under peculiar circumstances. 



*' Several other lakes exist in our immediate vicinity, around whoso shores the 

 parallel ridges and lines of boulders mark the ancient action of the same causes. 

 The third lake exhibits this agency very finely; and a very extensive marsh, in- 

 cluding about 1,500 acres of bog and peat, ten miles west of this place, shows a very 

 splendid specimen of this natural waU-building, several miles in length. This is 

 Lake Menona, which forms the south-east boundary of our city. This marsh, like 

 most other marshes, was the basin of an ancient lake, and the distribution of ita 

 boulders marks its outer limits. It is not uncommon for the ridges and walls to 

 be pushed up much higher than the adjacent land outside. There is no difiiculty 

 in supposing, therefore, that the water in the lake might thus stand at a level 

 above the land beyond the bank forming its barrier. 



I see nothing in the Iowa case that should constitute it an exception. In 

 your minute observation in the West, you must have encountered frequent cases of 

 this kind. ' Edwaed Dajv^iels." 



To Geo. P. Delaplaine, Esq. 



The Enclosed Frogs. — " I have read with pleasure the interesting account of 

 the frog found in the Dundalland colliery, ninety yards below the surface, by Mr. 

 Wardlaw Ramsay, given at page 352 of the Geologist. It unfortunately appears 

 that such discoveries are beset with difficulties, on account of miners being 

 unprepared for the sudden appearance of living reptiles in the progress of their 

 operations, or perhaps not having their interest sufficiently awakened as to induce 

 them to notice the particulars of such occurrences. But surely this subject is 

 sufficiently interesting and important to induce both the zoologist and the geologist 

 to endeavour to ascertain the property by which frogs or toads ore enabled to 

 -tistain life under circumstances in which they are excluded apparently from air 

 and food. The late Dr. Buckland, as you, Sir, have observed at page 253, besto^ved 

 much attention to this very subject, and actually enclosed several sijecimeus of the 

 common toad in limestone ; unfortunately, they all died after a short time. It has 

 been observed that probably his experiments would have succeeded better had the 

 creatures been taken directly from their natural habitats, instead of from the melon- 

 pit in which they were kept previously to their incarceration in stone. In the 

 "Magazine of Natural History," vol. Ill,, new series, page 518, is an account of a 

 toad being taken alive out of the ground, after being buried three feet below the 

 surface in flint-gravel ; having remained there undisturbed, under a small flowei'-pot, 

 three years all but ten days. It lived three days after its removal from its dormi- 

 tory. Another living toad was then consigned to the same three-feet deep exca- 

 vation, and, after full three years, was taken out of the ground alive from under 

 the same flower- pot ; this animal died eight days after. — "Magazine of Natural 

 History," vol. X,, page 180. Had the natural habits of these animals been better 

 attended to after being taken out of the ground, they probably would have 

 survived much longer. In the instances referred to no food was ofiered them after 

 their long abstinence, neither was any care taken of them, as ought to have been 

 done considering the importance of the experiments. — John Eeoavn, E.G.S., 

 Stanway." 



Fish Remains in Bituminous-Shale. — " Deafv Sir, — As many of your readers 

 may not be aware of the interesting fossils contained in the coal-measures, I beg 

 to intimate to such as reside in those districts that it will ^^pay research to 



