. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. TIME CONSIDEEATIONS. Fig. 20. These coarser rocks, owing to their tendency to undergo a mechanical disintegration, or disaggregation, may also yield to the decomposing agencies more readily than those of finer grain, though from the fact that they first fall away to coarse sand, whereby the rock- like character is lost, one might, on casual inspec- tion, be led to the oppo- site eonclusiom It need scarcely be said that, among rocks haying the same composition, whe- ther fragmental or crys- talline, siliceous or cal- careous,
. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. TIME CONSIDEEATIONS. Fig. 20. These coarser rocks, owing to their tendency to undergo a mechanical disintegration, or disaggregation, may also yield to the decomposing agencies more readily than those of finer grain, though from the fact that they first fall away to coarse sand, whereby the rock- like character is lost, one might, on casual inspec- tion, be led to the oppo- site eonclusiom It need scarcely be said that, among rocks haying the same composition, whe- ther fragmental or crys- talline, siliceous or cal- careous, those of a granu- lar structure will un- dergo disintegration more quickly than will those in which the individual minerals are closely com- pacted or interknit, as in many quartzites and dia- ba*ses. (2) Rate of Weather- ing influenced by Com- position.— Among rocks of the same structure as regards crystallization and size of particles, the basic varieties, such as the diabases and gabbros, as Mierostriicture of sandstone (Mg. 20), show- ^ rule SUCCUmb more read- ing relatively large amount of interstitial .-, ,-, -, .-t --, space and absorptive power, and (Fig. 21) ^^^ ^^^^ ^^ ^^^ ^^^® ^^^^ of diabase, with relatively little. varieties like the granites. This for the reason that the iron-magnesian as well as the soda-lime minerals are more suscep- tible than are the potash silicates and other essential constituents. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Merrill, George P[erkins] 1854-. New York, London, The Macmillan company
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectpetrolo, bookyear1913
