Renews — Prof. Geikie's Geological Map of Scotland. 129 



made familiar and attractive to him, but forced to found his ideas 

 respecting the rest of the geological world upon the data furnished 

 by the discoveries and speculations of others. Scattered as these 

 are in the maps and memoirs of the Survey, and in the pages of 

 multifarious and often inaccessible scientific publications, he cannot 

 be sufficiently grateful to those who have the opportunity and 

 patience to reduce this mass of heterogeneous material to order, and 

 bring a summary of the moi'e important results before his eyes at a 

 single glance in a general geological map like the present. 



We know of no other map of this class in which this task has 

 been so perfectly and so conscientiously performed. Prof- Geikie, in 

 his official capacity as head of the Scotch Survey, enjoys exceptional 

 advantages in the command of numberless geological details as yet 

 unpublished, and in his perfect familiarity with the ground mapped 

 by himself and his subordinates. But he also brings other and far 

 more vital qualifications to the execution of his task. No one has 

 personally added more to our knowledge of the physical structure 

 of Scotland, or has thought more profoundly over the many unsolved 

 problems of its geology. There ai'e few districts in the country to 

 which his eloquent writings have not imparted a new interest ; and 

 there is scarcely a single formation in its geological series in which 

 he has not added to our previous knowledge by discovery or original 

 observation. To him also is mainly due that excellent little map of 

 Scotland published hy Johnston in 1862, in which the so-called 

 Laurentian, Cambrian, and Silurian rocks of the Highlands were 

 laid down, and the first successful attempt was made to delineate 

 with correctness the distribution and mutual relationships of the 

 Scottish deposits in general. 



In the compilation of his facts the author has not only availed 

 himself of the vast mass of new details worked out by himself and 

 the officers of the Geological Survey, who have now practically 

 finished the mapping of that portion of Scotland lying to the south 

 of the metamorphic rocks of the Highlands, but he has profited to 

 the full by the facts detected in other areas by Harkness, Jamieson, 

 Judd and others. The topography of the map is by Mr. T. B. 

 Johnston, and is perfect in its way. By the omission of all hill- 

 shading, and by the use of skeleton-letters for the names of the 

 chief natural features, etc., much of the ground of the map is left 

 bare, and room is thus gained for the insertion of a large amount of 

 geological detail. 



The system of colouring adopted is that which has long been in 

 use in the publications issued by the Geological Survey of Britain 

 — the different shades of red being employed almost exclusively to 

 mark the various classes of igneous rock. This plan is so simple 

 and convenient in application, and so valuable as a distinct aid to 

 the memory, that it should be employed invariably upon all maps, 

 where several different formations are represented. One other 

 feature of this map cannot be too strongly commended. With one or 

 two minor exceptions — and these perhaps unavoidable — all the tints 

 are quiet in tone. We have none of those painful contrasts of faint 



DECADE II. VOL. V. — NO. III. 9 



