Page:Popular Science Monthly Volume 52.djvu/269

Rh researches he paid special attention to the lithological changes of the strata and to the fossils. In consideration of this earlier work he was awarded the Wollaston medal by the Geological Society.

Having acquired some familiarity with the geology of France by his former residence as a student and his frequent business there, Mr. Prestwich, in the course of the studies which resulted in the rearrangement of the Tertiary formations, carried his explorations across the Channel to the corresponding formations of France and Belgium, for the purpose of determining the correlation of the strata. In the course of these investigations, at the suggestion of Dr. Hugh Falconer, and in company with Sir John Evans, he examined the valley gravels containing flint implements—works of man—associated with the remains of extinct animals, the discovery of which in the valley of the Somme had been announced by M. Boucher de Perthes without attracting special attention. The finds made here could be compared with the somewhat similar discoveries made in England in Kent's Cavern by McEnery and in Brixham Cave in 1858. All these evidences of man's antiquity, together with others subsequently found in England, were studied by Prestwich and Sir John Evans, with the result of fully establishing the contemporaneous existence of man with other Pleistocene mammals. The question of the duration of man's existence upon the earth thus became a subject of lively discussion, which still continues. The theory of man's extreme antiquity, as indicated by these remains, which Mr. Prestwich was inclined to embrace at the time, and which he was among the first to promulgate in England afterward, underwent a process of modification in his mind, and he was disposed in his later works to reduce considerably the estimates he made then. In recognition of his work as one of the pioneers in establishing the geological antiquity of man, the Royal Society in 1865 awarded him the Royal medal.

As Dr. Prestwich grew older he paid more and more attention to economic geology, and finally became one of the most eminent authorities in that branch. His earlier studies on Coalbrookdale and the Tertiary strata seem, in the light of after developments, to have been preparatory, though unconsciously so, for such a career. A lecture on the geology of Clapham—The Ground Beneath Us—delivered about forty years ago to a local society, and his publication on the water-bearing strata of the country around London, were in that direction. The former work "has stood the tests of time remarkably well," and the latter, first published in 1851, has become a standard, and has lately been reissued with appendices. He was engaged upon the Royal Commission on Metropolitan Water Supply and upon the Royal Coal Commission, to the reports of which he