216 



THE GEOLOGIST. 



faithfully J. R. C."— " Sir,— I have collected fossils for the last two years, more 

 esTjecially those from the chalk, but I find it extremely difficult to prevent teeth, 

 &c. from breaking off. I have used thick gum-water for sticking the specimens 

 together, but I find it very unsatisfactory, in consequence of gum being acted upon 

 by the weather. 1st. Can you recommend me any good cement of which chalk 

 will not absorb all the moisture, and which will not show a black mark where the 

 specimens are jomed 1 2nd. Have geologists ever found any fossil pearls among 

 the oyster and other beds of fossil shells Yours, «&c. Enquirer."— 1st. All 

 chalk specimens should be saturated in a weak solution of gum, size, or other 

 similar material, before the joining of the fragments is attempted. Ackerman's 

 cement, procurable at those well-known artist's colourmen's establishment in the 

 Strand, is a very useful preparation for repairing chalk and other fossils. 2nd. 

 Fossil pearls have been, although rarely, found. Specimens from the large Inoce- 

 rami of the chalk have been long known. One very large and beautiful specimen 

 is in the collection of N. T. Wetherell, Esq. of Highgate, and has been described 

 in the "Annals of Natural History." 



Original Thickness of the Purbeck Dirt-bed. — " Sir, — In the volume of 

 The Geologist for 1858, is an article on ' Voices from the Rocks,' (p. 543). 

 It is admitted by the author of that book, that the dirt-bed in the Isle of Portland, 

 from whence so many fossil trees have from time to time been extracted, is from 

 12 to 18 inches in thickness. 



" I had the pleasure of visiting that interesting dirt-bed a few years ago, and it 

 struck me at the time that the bed of mould was originally very much thicker 

 when it formed part of the surface, and when the trees were growing upon it, and 

 before the bed of hard and compact limestone, 9 feet 7 inches thick, was depo- 

 sited over it. "* 



" The enormous pressure of such a mass of stone upon such a bed of vegetable 

 soil as the dirt-bed then was, must have greatly reduced its thickness. 



" We ought also to consider the effect which long periods of time would have 

 on such soil, from the escape of the various gases which compose the humus 

 always present in larger or smaller quantity in all soils. 



" With regard to trees thriving on a thin soil, I beg to observe that about seven 

 or eight years ago, at a slate-quarry at Swithland, near Leicester, I saw a thrifty 

 young oak having a trunk 2 feet in diameter, growing upon a large accumulation 

 of fragments of slate, the refuse of the quarry, and thriving apparently without 

 any soil except that formed of the fragments of slate. 



" This oak I thought was also a good memorial of the ancient date of the former 

 working of the slate-quarry. — John Brown, F.G.S., Stanway." 



Shoal of Fish buried in Sand. — The following extract is from a paper 

 entitled " A Week in Gaspe," by Dr. Dawson, m the Canadian Naturalist, for 

 October last : — 



" On the long sand-point that, stretching far into the bay, shelters the harbour 

 along which we walked in search of whales' bones and shells, I observed an 

 appearance new to me, and of some geological interest. Shoals of the American 

 ' Sand-Launce ' {Ammodytes A mericanus), a little fish three or foiu: inches in length, 

 had entered the bay, and either seeking a place for spawning or for sheltering 

 themselves from their numerous enemies, had ran into the shallow water near the 

 point, and, according to their usual habit, had in part buried- themselves in the 

 sand, which they throAv up by means of their long pectoral fins. In this situation 

 countless multitudes had died or been thrown on shore by the surf, and the crows 

 were fattening on them, and the fishermen collecting them in barrels for bait : 

 acres of them still remaining, whitening the bottom of the shallow water with 

 their bodies. It was impossible not to be reminded by such a spectacle of the beds 

 full of capelin in the post-pliocene clay of the Ottawa, and the similar beds 

 filled with fossil fishes in other beds as far back as the Old Red Sandstone. 

 Geologists have often sought to account for such phenomena, by supposing sudden 

 changes of level or irruptions of poisonous matter into the water ; but such 

 catastro]-thes are evidently by no means necessary to produce the effect. Here, in 

 the (piiet water of Gas]ie Bay, year hy year, immense quantities of the remains 



