Aug. 1, 1870.] 



HARDWICKE'S SCIENCE-GOSSIP. 



171 



of coarse-grained granite, containing much quartz, 

 there is actually more proof of the action of water 

 than of dry, igneous fusion. It is more than pro- 

 bable, therefore, that pressure, heat, and water 

 combined, in the deeply-seated parts of the earth's 

 crust, would cause the rocks to be reduced to a 

 kind of paste, and that this paste would be some 

 variety of granite. I can hardly enter into the 

 abstruse details of the deductions which have been 

 made from the chemical and microscopical exami- 

 nations of myself and relatives. Suffice it to say 

 they result in proving that pressure, and this, 

 generally speaking, of overlying rocks stratified or 

 otherwise, is a preliminary and indispensable 

 necessity to the formation of granite ; that, if 

 pressure be absent or less than that required, not- 

 withstanding all the other requirements may be 

 present— such as heat, similarity of mineral ingre- 

 dients, &c. — such a resulting igneous rock would not 

 be granite ! It might be a variety of porphyry, or 

 basalt, or greenstone, or, if all pressure were re- 

 moved, and the molten matter allowed to cool in 

 the open air, simply ordinary Lava ! Fronf a micro- 

 scopical examination of various granites, it has been 

 shown that those of the Highlands of Scotland 

 indicate their having been formed under no less a 

 pressure than 26,000 feet of overlying rocks more 

 than were the granites of Cornwall. There is good 

 reason for believing the latter to have required at 

 least 40,000 feet of rock-pressure ; so, in that case, 

 the granites of the Highlands must have been 

 formed when 66,000 feet of overlying rocks were 

 piled above them ! 



One is naturally astounded by the magnitude of 

 these operations, but I assure my hearers there is 

 little doubt as to the general correctness of the 

 deductions. In this way the mineralogical con- 

 struction of myself and others supplements the 

 teaching of organic remains as to the immense 

 antiquity of the globe ! Nothing short of an 

 eternity of time would have sufficed for all the 

 changes which have been rung upon it. There is 

 reason to believe many of my granitic relations are 

 nothing more or less, than re-melted stratified 

 rocks, and their enclosed fossils ! As these have 

 been slowly depressed or submerged, so as to bring 

 the lowest-seated portions within the; influence of 

 the earth's internal heat, they have been first 

 metamorphosed into a similar condition to gneiss 

 and mica-schist, and, if the sinking went on, have 

 passed through this stage into that pasty condition 

 which deprived them of all stratified structure, and 

 converted them into what I am myself ! Then suc- 

 ceeded a reversal of the \ movement ; so that this 

 granite would be thrust slowly upwards with all 

 the overlying strata piled above it. The movement 

 went on until these were tilted into a continuous 

 mountain-chain, or high and extensive table-lands. 

 Meantime the granite nucleus would form the heart 



of such mountains, the strata dipping away, as in 

 the Himalayas. 



I fancy I hear some of my listeners remarking— 

 "But if granite can only be formed under such 

 immense pressure, how is it we find such large areas 

 of country where nothing else is to be seen ? " In 

 the answer to this we have the gist of the argument, 

 and I would respectfully ask the special attention of 

 my audience to it. Let them ask themselves where 

 the materials came from to form the Laurentian, 

 Cambrian, Silurian, Devonian, and, in short, all the 

 other subsequent formations ? They could only 

 have been formed out of the waste of still older and 

 already solidified rocks. Each formation, therefore, 

 represents the amount of wear-and-tear which went 

 on during the period when it was deposited. If 

 there had been no compensation against this levelling 

 process, all the prominences would soon have been 

 worn down to a common level, and the elaboration 

 of more recent deposits been self-checked. But each 

 succeeding formation shows that this was not the 

 case, but indicates that the physical arrangements 

 of our planet have been much the same through 

 all time to what they are at present ; that atmo- 

 spherical and marine wear-and-tear were counter- 

 balanced by upheaval from beneath ; that the ex- 

 terior force emanating from the sun and resulting 

 in all these atmospherical effects, was exactly ad- 

 justed by the native force of the earth, exerted from 

 the interior outwards. These two have been in 

 equable counterpoise from the beginning, otherwise 

 the great life- scheme of our globe would never 

 have had time for its development ! 



I hope I have been successful in explaining a great 

 difficulty, and that my listeners now see the reason 

 why I and my relatives come to the surface. It is 

 because the rocks which overlay me at my birth 

 have since been stripped off and slowly removed by 

 atmospheric agencies. All the formations which 

 were then piled above me, are to be found in strati- 

 fied rocks of later date ; therefore, the period of my 

 birth is not limited to any particular geological 

 epoch. I am found at the surface, surrounded by 

 rocks of every age, even including those of the 

 Tertiary. Wherever the pent-up force of the earth's 

 interior has thrust us up, there have we slowly ele- 

 vated the rocks lying upon us. In many cases this 

 elevation has been so slow that it has hardly 

 exceeded the rapidity with which these overlying 

 rocks have been denuded away! Think of the vast 

 antiquity of our earth's crust, as indicated by these 

 facts alone ! Since the granites of the Highlands 

 of Scotland were formed, twelve miles of overlying 

 material must have been removed ! Where has it 

 all gone to ? Ask the nineteen miles in vertical 

 thickness of the known stratified rocks, all of which 

 have probably been formed since the granite itself. 

 We scarcely need be afraid of Time, when we have 

 Eternity to draw upon ! 



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