(Download) "Thoughts on a Pebble: A First Lesson in Geology" by Gideon Algernon Mantell # eBook PDF Kindle ePub Free
eBook details
- Title: Thoughts on a Pebble: A First Lesson in Geology
- Author : Gideon Algernon Mantell
- Release Date : January 31, 2021
- Genre: Geology,Books,Science & Nature,Earth Sciences,Ecology,Life Sciences,Geography,
- Pages : * pages
- Size : 1478 KB
Description
Upon examining this stone I discover that it is but the fragment of a much larger mass, and has evidently been transported from a distance, for its surface is smooth and rounded, the angles having been worn away by friction against other pebbles, produced by the agency of running water. I trace the stream to its source, half way up the hill, and find that it gushes out from a bed of gravel lying on a stratum of clay, which forms the eminence where I am standing, and is nearly 300 feet above the level of the British Channel. From this accumulation of water-worn materials the pebble must have been removed by the torrent, and carried down to the spot where it first attracted our notice; but we are still very far from having ascertained its origin. The bed of stones on the summit of this hill is clearly but a heap of transported gravel—an ancient sea-beach or shingle—formed of chalk-flints, that at some remote period were detached from their parent rock, and broken, rolled, and thrown together, by the action of the waves. We are certain of this because we know that flints cannot grow; that they were originally formed in the hollows or fissures of other stones; and upon inspecting the pebble more attentively, we perceive, not only that such was the case, but also that it has been moulded in Chalk, for it contains the remains of certain species of extinct shells and corals, which are found exclusively in that rock. Here then a remarkable phenomenon presents itself for our consideration; this flint, now so hard and unyielding, must once have been in a soft or fluid state, for the delicate markings of the case and spine of anEchinus, or Sea-Urchin, are deeply impressed on its surface; and a fragile shell with its spines, is partially imbedded in its substance.[C] Nay more, upon breaking off one end of the pebble, we find that a sponge, or some analogous marine zoophyte, is entirely enveloped by the flint; and also that there are here and there portions of minute corals, and scales of fishes. What a "Medal of Creation" is here—what a page of nature's volume to interpret—what interesting reflections crowd upon the mind!
"Flints cannot grow."—Here I would digress for a moment to notice an opinion so generally prevalent, that perhaps some of my young readers will not be prepared at once to answer the question—Do stones grow? The farmer who annually ploughs the same land, and observes a fresh crop of stones every season, will probably reply in the affirmative; and the general observer who has for successive years noticed his gardens and plantations strewn with stones, notwithstanding their frequent removal, may possibly entertain the same opinion; but a little reflection will show that stones cannot be said to grow or increase, in the proper acceptation of the term. Animals and plants grow, because they are provided with vessels and organs by winch they are capable of taking up particles of matter and converting them into their own substance; but an inorganic body can only increase in bulk by the addition of some extraneous material; hence stones may become incrusted, or they may be cemented together and form a solid conglomerate, but they possess no inherent power by which they can increase either in size or number—they cannot grow.