Identifier: quarterlyjourna101854geol (find matches)
Title: The Quarterly journal of the Geological Society of London
Year: 1845 (1840s)
Authors: Geological Society of London
Subjects: Geology
Publisher: London (etc.)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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. Conclusion.—On the whole, then, I conclude that pipes and fur-rows have been formed by the mechanical action of water, before thematter with which they are filled was deposited ; and the nearestexisting analogies I can find to them are the effects of breakers onthe shore, and of the action of torrential rivers. Their general distribution may be explained by the continuedadvance or retreat of the coast-line, during the repeated risings andfallings of the land throughout the tertiary era. The difference inmagnitude between these ancient excavations and those now beingformed by the sea, may be ascribed to the greater magnitude ofwaves, occasioned by the movements to which the land, quiescentnow, was subject then. The prevalence of cylindrical cavities in the * Quart. Journ. Geol. Soc. vol. i. p. 315. t Quart. Journ. Geol. Soc. vol. vii. p. 26. t See Table, Quart. Jouru. Geol. Soc. vol. ix. p. 295. § Quart. Journ. Geol. Soc. vol. vii. p. 382, &c. 1854.) TRIMMER ON SAND-PIPES. 239
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240 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. (Jail. 18, chalk, in connexion with furrows, and their comparative rarity insand, gravel, and clay, in which furrows prevail, may be due to thegreater solidity of the chalk. It may also be partly due to its cal-careous composition; for, though I contend for the prevalence ofmechanical action in the formation of these cavities, I do not exclude,that chemical action which water always exercises by means of thecarbonic acid which it absorbs. Lieut. Newbold * observed that,while some of the rivers of India, in times of flood, excavated in theirrocky beds basins of the different shapes which we find in the chalk,these cavities, when the river contracted its volume during the dryseason, were left filled with stagnant water, and this water, by itschemical action, softened the gneiss in such a manner as greatly tofacilitate the boring process during the ensuing rainy season. Simi-lar alternations between vorticose and stagnant water, the one actingme

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