PROCEEDINGS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. dxXV 
Hutton and Hall in Scotland, William Smith in England, and 
Werner in Germany had already completed their labours, but beyond 
these names there had been comparatively few workers in the field. 
From this time onward, however, the number rapidly increased. Of 
these, the most prominent names in the early years of the reign were 
Sedgwick, Lyell, and Murchison, whose long years of activity were 
nearly coincident with each other, all three having been born about 
the end of last century, and having died early in the seventies. 
During that time they accumulated an immense mass of facts bearing 
more especially on systematic Geology, Sedgwick’s work being 
chiefly devoted to the Cambrian group of the Primary Rocks and 
Murchison’s to the Silurian. Lyell’s name, however, will be 
remembered chiefly on account of his epoch-making generalisations. 
He was the first to demonstrate that the forces which are at work 
on the earth’s surface are the same as those which have been in 
operation throughout all geological time. This discovery revolu¬ 
tionised Geology and changed it from a system of fantastic theories 
into a Natural Science in the truest sense of the term. It showed, 
in fact, that the building up of the earth’s crust, like all other 
processes in Nature, had been one of gradual development through 
the operation of natural laws. 
The Geological Survey of Great Britain was commenced about 
the beginning of the reign, the first volume of its Memoirs being 
published in 1846. Shortly afterwards the Surveys of India and 
Canada were commenced, and since then the greater part of the 
United States of America, and of most European countries have 
been more or less carefully surveyed and mapped. The result of all 
this official scientific work, carried on at the expense of the respective 
countries, has been the addition to our knowledge of an immense 
store of facts, which could not have been accumulated by private 
enterprise. Fortunate it is for this Science that the hope of in¬ 
creasing the mineral wealth of nations has been the means of 
fostering its pursuit by the aid of the public purse. This official 
recognition, however, has not by any means had the effect of stifling 
private inquiry, as is evident from the number of Geological Societies 
which were founded shortly before and shortly after the beginning of 
the reign, including those of London, Dublin, Edinburgh, Glasgow, 
Manchester, and Liverpool. The publications of these Societies 
form another storehouse of facts which are often useful in checking 
the results of the official survey. In our own country we have 
a striking example of this in the history of the investigation of the 
rocks of the North-West Highlands, where first Professor Nicol and 
afterwards Mr. Charles Lapworth were able to unravel the com¬ 
plicated succession of these rocks. The latter observer has demon¬ 
strated that our Highland hills form the basal section of an ancient 
Alpine chain. Mr. Lapworth’s generalisations, regarding the great 
ridges and hollows of the earth’s crust and its lines of weakness, are 
amongst the most important contributions to modern Geology. 
In no department of Geology has greater progress been made 
than in that of Petrology. Indeed, this Science may almost be said 
to have sprung into existence within the last seventy years, for it was 
