24 DR GEIKIE ON THE HISTORY OF VOLCANIC ACTION 



the second volume of the Transactions of the Geological Society, some remarks by him 

 on specimens from that district transmitted to the Society. For several years in 

 succession he devoted himself with great energy and enthusiasm to the self-imposed 

 task of geologically examining and mapping all the islands that lie to the westward of 

 Scotland, from the remote St Kilda even as far as the Isle of Man. From time to time, 

 notices of parts of his work were given in the Transactions of the Geological Society. 

 But eventually in 1819 he embodied the whole in his Description of the Western 

 Islands of Scotland. 



This great classic marks a notable epoch in British geology. Properly to estimate its 

 value, we should try to realise what was the state of the science in this country at the 

 time of its appearance. So laborious a collection of facts, and so courageous a resolution 

 to avoid theorising about them, gave to his volumes an altogether unique character. 

 His descriptions were at once adopted as part of the familiar literature of geology. His 

 sections and sketches were reproduced in endless treatises and text- books. Few single 

 works of descriptive geology have ever done so much to advance the progress of the science 

 in this country. With regard to the special subject of the present memoir, Macculloch 

 showed that the basalts and other eruptive rocks of the Inner Hebrides pierce and over- 

 lie the Secondary strata of these islands, and must therefore be of younger date. But 

 though he distinguished the three great series of " trap-rocks," " syenites " and " hyper- 

 sthene-rocks " or " augite-rocks," and indicated approximately their respective areas, he did 

 not attempt to unravel their relations to each other. Nor did he venture upon any 

 speculations as to the probable conditions under which these rocks were produced. He 

 claimed that those who might follow him would find a great deal which he had not 

 described, but little that he had not examined. Subsequent observers have noted many 

 important facts, of which, had he observed them, he would at once have seen the meaning, 

 and which he certainly would not have passed over in silence. But as a first broad out- 

 line of the subject, Macculloch's work possesses a great value, which is not lessened by 

 the subsequent discovery of details that escaped his notice, and of points of geological 

 structure which he failed to discover. 



It may here be remarked, that among the earliest and ablest observations of the 

 volcanic rocks of this country were those made by foreigners. In some cases, students 

 who had repaired from abroad to Edinburgh for education caught the geological 

 enthusiasm then so marked in this city, and made numerous journeys through the 

 country in search of further knowledge of its rocks and minerals. In other instances, 

 geologists of established reputation, attracted by the interest which the published 

 accounts of Scottish geology had excited, were led to visit the country and to record their 

 impressions of its rock-structure. Of the first class of observers the two most noted were 

 Ami Boue and L. A. Necker. Boue took his degree of M.D. at Edinburgh in 1816. 

 During his stay in Scotland he made extensive tours across the kingdom, and acquired a 

 wide knowledge of its rocks and minerals. In the year 1820 he published his Essai 

 geologique sur VEcosse. The value of this work as an original contribution to the 



