Heroes of science

by P. Martin Duncan

Clermont-Ferrand.
May 26th, 1828.

My dear father,

I have just returned again to Clermont, from an expedition of five days, and we have discovered that there is no end to the work to be done in this country, and that it is of the most interesting description. The first day was spent in ascending some of the lofty volcanic Puys near here. Mrs. Murchison accompanied us, and then returned to Clermont, where she employed herself, during our absence, in making panoramic sketches, receiving several of the gentry and professors, to whom he had letters, in the neighbourhood, and collecting plants and shells, etc., while Murchison and I, with my man, went on in a patache, a one-horse machine on springs. We first visited Pontgibaud and the Sioule, to see the excavations made by that river in the grand lava-current of the Come, which descended from the central range, and dispossessed the river of its bed. The scenery was beautiful. Just as we were leaving the place, the peasants offered to take us to a volcano farther down the river. As no Puy was mentioned in Desmarest’s accurate map, nor by Scrope, we thought their account a mere fable; but their description of the cinders, etc. was so curious, that we had the courage to relinquish our day’s scheme, and proceed again down the river.

You may imagine our surprise when we found, within a ride of Clermont, a set of volcanic phenomena entirely unknown to Buckland, Scrope, or the natives here. A volcanic cone, with a stream of basaltic lava issuing out on both sides, and flowing down to the gorge of the Sioule. This defile was flanked on both sides by precipitous cliffs of gneiss, and the river’s passage must have been entirely choked up for a long time. A lake was formed, and the river wore a passage between the lava and the granitic schist, but the former was so excessively compact, that the schist evidently suffered most. In the progress of ages, the igneous rock, one hundred and fifty feet deep, was cut through, and the river went on and ate its way, thirty-five, forty-five, and in one place eighty-five feet into the subjacent granitic beds, leaving on one bank a perpendicular wall of basaltic lava towering over the gneiss. In the Vivarrais, where similar phenomena had been observed, Herschel had remarked a bed of pebbles between the lava and the gneiss, marking the ancient river-bed, but Buckland endeavoured to get over this difficulty by saying that these pebbles might have covered a sloping bank when the river filled the valley, and that this bank may have always been high above the river bed; for if the sloping sides of a valley, said the Professor, be covered with pebbles, as they often are, and the valley is filled with lava, and then the lava cut through and partially removed, there will of course be a line of pebbles at the junction of the lava and the rock beneath, but these pebbles will not mark an ancient river bed. Now, unluckily for the doctor in this case, he has no loophole; an old lead mine, said to have been worked by the Romans, happens to have exactly laid open the line of contact, and the pebble bed of the old river is seen going in under the lava, horizontally, for nearly fifty feet. This is an astonishing proof of what a river can do in some thousands or hundred thousand years by its continual wearing. No deluge could have descended the valley without carrying away the crater and ashes above.

Six hundred or seven hundred feet higher, is an old plateau of basalt, and if this flowed at the bottom of the then valley, the last work of the Sioule is but a unit in proportion to the other. There are several of the Clermont savans who, since they discovered how much we were interested with this, have given us to understand they intended to publish on it, but no doubt they will take a year before they launch out in the expense of a patache to Pontgibaud. Murchison certainly keeps it up with more energy than anyone I ever travelled with, for Buckland, though he worked as hard, always flew about too fast to make sure of anything. Mons. Le Coq, the botanist, a clever young man, assures me that the geology of the soils does not affect the botany of Auvergne. I shall get some specimens from him for Dr. Hooker, I expect. None to be bought, at least this year, for it seems there may be hereafter. It is a wonderful fact that Glaux maritima grows round some saline springs here. Busset, an engineer, who is mapping Auvergne, has forced us to dine with him to-morrow. As we know his object to be to get geology out of us, of which he knows nothing, M. fears it will be a bore, but the man is evidently clever. We shall get barometric heights from him, and a map of our little volcanic district, and if he pumps unreasonably, I shall find a difficulty in expressing myself in French. We are to meet Count Le Serres there, a gentlemanlike and well-informed naturalist, who has a property on Mont Dore, and knows more geology than anyone we have met here, professors not excepted. He organized a geological society here, and they chose Count Montlosier as president; but the Jesuits took alarm, and, declaring that Montlosier had written a book against Genesis, got the Prefect and Mayor and Government to oppose, and at last put the thing down; at least it merged in the regular scientific Etablissement de la Ville, and Montlosier is just coming out with a book against the Jesuits, a more popular subject in France at present than geology. We are to visit him at his château near Mont Dore. We like the people and the country.

Believe me, your affectionate son,

Charles Lyell.

TO HIS FATHER.

Bains de Mont Dore, Auvergne.
June 6th, 1882.

My dear father,