476 Reviews — The Survey Memoir on the Scottish Uplands. 



It was not, however, until 1888 that the officers of the Survey- 

 felt the necessity — or, to speak more accurately, found the time and 

 the opportunity — for testing the general reliability of these zonal 

 ideas in the Uplands as a whole, and of revising the geology in the 

 full light of the new methods. 



Looking back over the whole matter from our present standpoint, 

 we see that there is little or no room for astonishment or regret at 

 this delay. Although — and to their lasting honour be it said — the 

 new ideas were from the first heartily welcomed by the Geological 

 Societies, and adopted by the younger and more ardent geologists, 

 they were long looked at askance by many of those geologists well 

 qualified to judge of their value and their applicability. 



Consider for a moment the demands the novel results and con- 

 clusions due to the zonal method made upon the common-sense and 

 experience — I will not say credulity — of those British geologists 

 who had spent many of the best years of their life face to face with 

 Silurian rocks in the field, had often worked side by side with the 

 great leaders in reducing them to order, and had the literature of 

 the subject at their finger-ends. 



The data upon which the older views of the Upland succession 

 rested were those which naturally appealed to the experience of the 

 true field geologist. They were first and foremost petrological. 

 They were few in number, easy to obtain, and easy to interpret. The 

 sequence followed, as it were, almost of itself, from the common- 

 sense deductions which would be drawn by any ordinary geologist 

 taking broad views of every-day field phenomena. The tectonic 

 structure corresponding to this succession showed, even more con- 

 spicuously than usual, the deformed character of districts floored by 

 the more ancient rock formations. And lastly, the simple theoretical 

 picture this succession gave us of the physical conditions of the 

 region in Silurian times showed us little or nothing that previous 

 knowledge or opinion had not led us to expect. 



But, on the other hand, the newer views of the succession were 

 founded essentially upon palseontological considerations, and petrology 

 was relegated to a place in the background. They were dependent 

 upon the harmonizing of a host of minor and local details, always 

 difficult and sometimes impossible to obtain ; and the final results 

 were confessedly, after all, first approximations to the truth. In the 

 discussion of the bearing of these new results upon the Upland 

 structure, the evidence of the senses was put out of court, and field 

 experience and ordinary judgment flouted with paradoxes. Finally, 

 when from all the results thus arrived at we attempted an explanatory 

 picture of the physical conditions in Silurian time, the imagination 

 seemed to run riot amid the unfamiliar and the unexpected. 



If, in surveying these convoluted Upland strata, we restrict 

 ourselves to the older and simpler regional or formational methods 

 of mapping by broad mineralogical characters and visible super- 

 position, we are forced to disbelieve in the individual graptolite 

 species as a geological index. We are led quite naturally to the 

 earlier Survey view that the visibly ascending sequence of Upland 



