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HARDWICKE'S SCIENCE-GOSSIP. 



trary, formations of much more modern date than 

 that to which I belong are rich in quartz veins and 

 even beds. In short, any rock that has been ex- 

 posed to the same influences that I have, if it con- 

 tained the same chemical substances as myself, 

 would also have quartz as the result. They tell me 

 that I am chemically composed of only one sub- 

 stance — Silica. My normal condition is transparent 

 and colourless, although I am rarely found like this 

 except when in geometrically-shaped crystals. A 

 milk-white colour is that which I commonly affect; 

 and this is due solely to the rate at which my pa- 

 rent mass cooled down. Hence it is that geologists 

 can more or less tell from my appearance the cir- 

 cumstances which attended my birth. From the 

 pure, transparent condition I mentioned above, I 

 pass through a great "many modifications, and in 

 each stage of these I am known by different names. 

 But with the exception of very slight mixtures of 

 other ingredients than this same silica, .1 continue 

 the same throughout ; thus, when I am of a violet 

 tint I am called Amethyst ; when of the colour of 

 sherry, Topaz ; when'of a smoke-brown hue, Cairn- 

 gorm, &c. Mixed with other chemical substances 

 I pass into jasper, flint, chalcedony, agates, &c, in 

 all of which you will find that at least nine-tenths 

 of their whole bulk is silica. 



Up to the time when the geological formation to 

 which I belong had been discovered, as I before 

 remarked, the Cambrian was looked upon as the 

 oldest. But there were a series of schists, quartzose 

 rocks, &c, which were still older than these, and 

 which usually went by the name of Metamorphic, or 

 "altered" rocks'; thus committing them to no par- 

 ticular geological age. By many these rocks were 

 regarded as transitional, — that is, as passing from 

 an igneous to a stratified condition. When it was 

 imagined that all the granite rocks were formed as 

 the outer crust of a ouce molten globe, then, it was 

 also thought, the rocks which came to be formed 

 along the bottoms of the hot seas must be of a very 

 peculiar character. | In short, these mica-schist, 

 quartz, and gneissose'! strata' were regarded as 

 having been deposited and solidified under such 

 circumstances. Their absence of fossils, and proofs 

 of having experienced great heat, were looked upon 

 as bearing out this view. I hardly need tell you 

 how erroneous it was. The Cambrian period was 

 believed to be that when Life first [appeared on the 

 Globe. Now this supposition is known to be as 

 wrong as that which accounted for the'mineralo- 

 gical appearances of the metamorphic rocks. 



Although I am speaking only as a humble piece 

 of quartz, you must remember, that, when I am 

 narrating the circumstances of my life, I am at the 

 same time giving those of the mica-schist, gneiss, 

 and altered limestones, which, equally with myself, 

 belong to the Laurentian epoch. Indeed, the last- 

 named rock, greatly altered though it is in appear- 



ance, so as to resemble loaf-sugar, could, perhaps, 

 tell you more of the vital conditions of the ancient 

 Laurentian'seas than I can. Eirst, let me impress 

 you with the fact that when we were formed, 

 collectively, we did not differ in appearance from 

 the sandstones, 'clays, and limestones either of 

 the present or any bygone geological era. All 

 this wonderful alteration in our appearance and 

 structure is due solely to the subsequent changes 

 we underwent. Of these I shall speak presently. 

 If you know anything of the great deductions 

 of geology, you will be aware that the farther 

 you go back in time, the fewer and simpler are 

 the forms of life which inhabited the earth. It 

 was the general poverty of species, accompanied by 

 their lowly organization, which caused the Cambrian 

 epoch to be regarded as the first platform of Life. 

 Now when you go farther back in time, to my own 

 age, you will find that the organisms are still lowlier. 

 Indeed, of the objects that lived in the seas where I 

 was originally deposited as a thick sheet of ordi- 

 nary sand, all that I can remember is one abundant 

 organism, not more than an inch in diameter, now 

 known as Eozoon, or the "dawn-animalcule," in 

 allusion to its primeval antiquity. It] was lowly 

 enough organized, being' little above the natural 

 history rank of the common sponge. This marine 

 creature lived on the sea-bottom in vast quantities, 

 and there grew by the addition of layer on layer of 

 younger forms," just, as I am told, is the way in 

 which coral reefs grow in modern seas ! Like the 

 latter, it absorbed its carbonate of lime from the 

 sea- water, and thus caused great masses slowly to 

 accumulate. This was in the deeper parts of the sea, 

 where the water was clear, and free from muddy 

 sediment. But my recollection goes no farther to any 

 animal type. No fishes swam in the blue water ; no 

 crustacean crawled over where I lay ! Occasionally 

 the rivers brought some lowly-organized vegetables 

 in entangled masses, or sea-weeds drifted into my 

 neighbourhood, and eventually became entombed in 

 the sandy mud— my then condition. An impure coal 

 was thus formed, and when the rocks underwent 

 their great transformation by the agency of heat, 

 this vegetation somehow or another passed into 

 Plumbago, or " black-lead," as it is commonly and 

 erroneously called. The great amount of carbon — 

 more than there is in many kinds of actual coal — 

 which makes up the composition of plumbago, had 

 long indicated its vegetable origin. How lowly 

 organized were the land plants of the Laurentian 

 period you may guess at from the fact that many 

 ages afterwards, during the Carboniferous epoch, 

 they existed chiefly as gigantic club-mosses ! What 

 I have said about the vegetable origin of " black- 

 lead " applies as logically to the origin of the 

 Laurentian limestones. Some of the beds are as 

 much as fifteen hundred feet in thickness, but 

 altered throughout. As geologists are now aware, 



