Essay on the Theory of the Earth

by baron Georges Cuvier

[409] Vol. xiv. p. 205.

[410] The remarks on the connection of geology with agriculture and planting, are inserted here as an illustration of some of the details in the body of the work. They will, we think, be useful to students of agriculture and geology, and interesting to the general reader.

[411] The dryness depends chiefly, if not entirely, on the fissures or divisions in the rocky base of the soil; for, in some parts of Sologne in France, as stated by Mr Arthur Young, and in sundry districts of England, chalk and limestone bottoms are occasionally observed to be retentive and wet. Undergrounds, formed of chalk or limestone, have frequently a thin covering of vegetable mould, from their being, in some cases, over close and wet, and in others over open and dry; the former condition being unfriendly to vegetation and the formation of mould, and the latter too readily permitting its departure when formed, or otherwise favouring the decomposition and waste of that material.

[412] The reason here assigned is confirmed by some observations delivered by one of the latest and most intelligent of the English writers on agriculture. “If,” says Mr Marshall, “the several strata” (viz. the subsoil and base) “are of so loose a texture, as to permit the waters of rains to pass quickly downward, without being in any sufficient degree arrested by the soil, the land may be said to be worthless to agriculture.” He adds, “Before we suggest any improvement of lands of the latter description, it will be proper to premise, that many of the light sandy soils of Norfolk, which would otherwise be uniformly absorbed to a great depth, have a thin earthy substance, or ‘Pan,’ which intervenes between the soil and the subsoil, and which is of such a texture, as to check the descent of rain waters, and thereby retain them the longer in the soil, as well as to prevent the manure it contains from being carried away by their rapid descent; yet sufficiently pervious to prevent a surcharge of moisture from injuring the produce. To this fortunate circumstance is principally owing the fertility of the lands of East Norfolk: for wherever this filter happens to be broken by the plough, or otherwise, the soil becomes unfertile, and continues to be so for a length of years.”—(See Norfolk, vol. i. page 11.) “This fact aptly suggests the expedient of improving, or fresh forming, a filter of this kind; seeing how capable it is of producing so many valuable advantages; the more especially, as it is probably the Norfolk pan owes its origin to fortuitous art, rather than to nature.”—(See Norfolk, vol. i. page 12.) “A millstone, or other heavy wheel-shaped stone, made to run upon its edge, in the bottom of the plough-furrow (the thickness of its edge being equal to the width of the furrow), by the help of an axle and wheels, would greatly compress a light, porous subsoil. The idea of forming a pan artificially, struck me first in Norfolk; and time and experience have strengthened it. If the experiment be made on a compressible subsoil, as sandy loam, or the soft rubble which sometimes intervenes between an absorbent soil and an open rock, there can be little doubt of its success. But on loose open gravel, which is not sufficiently mixed with tenacious mould to sheath it, and lying on an open base, less utility may be expected from it.”

[413] Vide Dr Adam of Calcutta’s Remarks on the Rocks and Soil of Constantia at the Cape of Good Hope, in an early number of the Edinburgh Philosophical Journal.

[414] The ochre yellow colour of the decayed greenstone around Edinburgh, and in general in many trap districts in this country, is caused by the decomposition of the imbedded iron pyrites.

[415] The Streams of Obsidian in Iceland, Lipari, Peak of Teneriffe, Ascension, and Mexico, afford striking examples of the fact stated above.

[416] Those who feel disposed to examine the connection of Geology and Agriculture, will find many additional details and views given in Hausmann’s work, of which the above may be considered in some degree as a condensed view.

[417] John Hart, Esq. Member of the Royal College of Surgeons in Ireland, some time ago sent to me a copy of a very interesting tract entitled “A Description of the Skeleton of the Fossil Deer of Ireland, Cervus megaceros; drawn up at the instance of the Committee of Natural Philosophy of the Royal Dublin Society.” The details in the text are extracted from Mr Hart’s memoir, and the engraving of the Elk is copied from Mr Hart’s lithographic delineation.

[418] In a Report which Mr Hart made to the Committee of Natural Philosophy of the Royal Dublin Society, and which was printed in their Proceedings of July 8. 1824, he alluded to an instance of a pair of these horns having been used as a field gate near Tipperary. Since that he has learned that a pair had been in use for a similar purpose near Newcastle, county of Wicklow, until they were decomposed by the action of the weather. There is also a specimen in Charlemont House, the town residence of the Earl of Charlemont, which is said to have been used for some time as a temporary bridge across a rivulet in the county of Tyrone.