sept. 1899] THE SILURIAN ROCKS OF BRITAIN 217 



as a matter of vastly greater importance than the history of the fossils occurring 

 in the strata which that dyke happens to cross. Whether the dyke consisted 

 of basalt or of " melaphyre," or whether it should be called a dolerite or a 

 " diabase," has in Scotland only too often been considered a question of far 

 greater importance than whether the graptolites which occur in the strata 

 traversed by that dyke indicate that the rocks are of Arenig age, or whether 

 they date from Wenlock times, or, again, whether they represent any period of 

 intermediate age. We cannot all be specialists, it is true ; but, clearly, every 

 modern geologist should be familiar with at least the zonal fossils of the rocks 

 amongst which he is at work. One would also think that his work would 

 prove of much greater interest to him if he knew something of the biological 

 relationships of the organic remains with which he is likely to meet. As things 

 stand at present, it may be confidently stated that, taking the whole of Scot- 

 land, the number of those who are really working at fossils of any kind may be 

 counted on one hand — one of the authors of the present work being one of 

 them. And even the number of those who are systematically making collec- 

 tions of fossils probably does not exceed a score. The case, of course, is very 

 different south of the Border, where nearly every geologist takes a more or less 

 keen interest in Palaeontology. 



That these defects will soon be made good no one who carefully studies the 

 most admirable historical introduction given in one of the earlier chapters of the 

 book under notice can for a moment doubt. The whole of that history leads up 

 to a triumphant vindication of the claims of Palaeontology to occupy a foremost 

 place in the studies of all geological students in the future, not only on account 

 of the light which that science throws upon the evolution of existing forms of life, 

 but also on account of the invaluable aid it affords in unravelling the complicated 

 structure of districts like that of Girvan, or of the Valentians or Southern 

 Uplands of Scotland. Had it not been that Professor Lapworth brought to 

 bear upon the rocks of these districts a combination of skill in field work with 

 an extensive knowledge of Palaeontology, we should probably still have been 

 no wiser regarding the true history of the rocks in question than we were thirty 

 years ago. 



On taking up the work whose contents have suggested these remarks, the 

 reader will do well to give a full consideration to the section of the book 

 referred to. He will find in it evidence of a strongly-marked desire on the 

 part of the authors to deal in a generous spirit with the work of all previous 

 observers, and he will further see how each man has added something of his 

 own to our knowledge of these difficult rocks, and how that intellectual giant 

 amongst geologists, Professor Lapworth, largely by working out the zonal 

 distribution of the Graptolites, has enabled us, in the end, to gain a clear view 

 of the true succession of the Scottish Ordovician and Silurian Kocks. By the 

 light thus presented, Messrs. Peach and Home, with Mr. Macconochie, have 

 laboriously worked over the whole area where these rocks occur, and, bringing 

 to bear upon them the results of wide experience, they have completed the 

 survey of the whole area of which this book treats. It is from the vast mass of 

 material collected in the course of this work that Mr. Home has completed the 

 present Memoir. No one who takes the trouble to read any section of it 

 can fail to see that, in all respects, it forms a perfect model of what such a book 

 should be. It may truly be said to present all that can be known at present 

 regarding the geology of the group of rocks to which it specially refers, and 

 Sir Archibald Geikie is to be congratulated on the production by his staff 

 of a Survey Memoir in which the work of eminent specialists like Mr. Teall, 

 Professor Lapworth, Dr. Traquair, as well as Professor Laurie and Mrs. Robert 

 Gray, has been skilfully incorporated with the vast mass of information collected 

 by the above-named members of the field staff of the Survey. 



It may be well to mention here that the various geological maps, rock 

 specimens, and most of the fossils, referred to in the Memoir, are exhibited in 



