Penny Blood: Serial Sensation and Working-Class Entertainment — page 269: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

25? SEQUENCE OF VOLCANIC ROCKS. [cu. xx. two normal magmas, an acid and a basic, mingled in definite proportions. Such will be the case with our lava, if the roots of the mountains have been formed out of a crust consisting in its lower parts of granitic rock beyond reach of the region penetrated by sedimentary deposits. But when we remember that all sedimentary deposits have been ultimately derived from these two normal magmas, it seems that, if samples of every sedimentary deposit proportional in mass to the whole deposit, were mingled together, we should obtain a mixture chemically equivalent to a mixture of the magmas. Accordingly, if many varieties of sedimentary rocks were to contribute their share to the fused matter, it might be difficult to say that the resulting rock had not been directly derived from the two magmas. It does not appear requisite therefore that, because a volcanic product conforms to the law of Bunsen, it should be necessary to exclude the presence of such small contributions as might be expected to be made by sedimentary rocks, de- pressed here and there into the region of fusion, as would happen if the views of Prof. James Hall and other American geologiste are correct’. It is now possible to account for the changes in the character of the lava which is emitted from the same volcano at different times. For the fused matter will be distributed in layers, that which is nearest to the bottom of the crust being the most similar to it in composition. It might happen that all this fused matter within reach of the vent might be erupted, and before it accumulated afresh, the lava of the next eruption might be supplied by a denser couche beneath. But before a third took place, the fused matter might have collected again, and possibly this time mingled with the substratum in a different proportion, Thus successive eruptions would produce different lavas. The volcanoes more distant from mountain ranges might be expected, on the whole, to erupt the more basic lavas. It would be worth while to inquire whether there ‘Is any reason to suppose this generally to be the case; for we gather from Richthofen, that certain basaltic fissure eruptions 1 p. 201. COMIC OOOKS.EO