3^6 Prof. Necker on the History and Progress of Geology. 
tion ; he described them with so much clearness, that, notwith- 
standing the changes effected in the nomenclature, we still, at 
the present day, easily recognise, by means of his descriptions, 
the rocks even the most difficult to distinguish. 
Embracing the study of the Earth in its most extended accep- 
tation, to the examination of minerals, and the stratification of 
rocks, he added that of the physical structure of mountain 
chains, of the form, direction, and probable origin of valleys ; he 
sought, in the present arrangement of strata, and in the disposi- 
tion of the fissures by which they are traversed, data for deter- 
mining their original position ; he recognised, in the action of ex- 
ternal agents, the operation by which they daily eat, by little 
and little, into those rocks, so hard and apparently so indestruc- 
tible. It was this which led him to observations upon the gla- 
ciers, the sno^YS accumulated, from time immemorial, upon the 
declivities of our Alps ; and it was still his desire of advancing 
physical geography, that gave rise to his labours in physics, and, 
in particular, to his Treatise on Hygrometry. Thus, with him, 
every thing converged tow^ard one object, — that of collecting ma- 
terials for the history of the globe. 
In proportion to the avidity with which he sought for facts, 
was the care with which he avoided vain speculations. If he 
sometimes advances a hypothesis, it is with a reserve justly ad- 
mired, although rarely imitated, and only when the facts seem 
imperiously to command it. When new facts come in opposi- 
tion to his former opinions, he abandons or modifies them with- 
out regret. 
He has even carried this wise restraint so far, that that com- 
prehensiveness of mind which, in the immensity of science, at- 
taches itself still more to what is to do, than to what has l^een 
done, may have been taken for a too great timidity in general^ 
ising his observations. But, if Saussure, after forty years of assi- 
duous study, in the part of the Alps comprised between the 
Tyrol and the Mediterranean, during which he attached him- 
self particularly to the central part of the ehaiuj the most diffi- 
cult to explore, and the most extensive, — if Saussure, in exposing 
the general results of his observations, has not been led to disco- 
ver that regular succession of formations which the German 
geologists were the first to detect; if he avows, that the countries 
