712 NATURAL SCIENCE. ^^y 



Geological Map of Scotland. By Sir Archibald Geikie, D.Sc, LL.D., F.R.S., 

 Director-General of the Geological Survey. Edinburgh : John Bartholomew 

 and Co., 1892. Price 6s. 

 vSTUDENTSof British Geology and travellers interested in the relations 

 between scenery and rock-structure, will welcome this nc\v Geological 

 Map of Scotland ; for the scale is sufficiently large to show the dis- 

 tribution of the principal groups of rocks, and the topograph)^ is 

 based on the latest Ordnance Survey. Moreover, the map is well 

 printed, and the colours, numerous as they are, clearly show the 

 various subdivisions of the rocks. 



It was thirty-one years ago when the "First Sketch of a New 

 Geological Map of Scotland, with Explanatory Notes," was issued 

 by Sir Roderick Murchison and Archibald Geikie ; and this map 

 was on a scale of 25 miles to an inch. It summarised our knowledge 

 at that date, recording work done by Macculloch, Nicol, Harknesa, 

 and others, and that done in a portion of the south of Scotland by 

 the Geological Survey. Much original work was likewise incorpo- 

 rated, for Skye and Raasay, and parts of Islay and Jura, and the 

 Highlands, had been personally surveyed by A. Geikie ; while 

 Sutherland and Caithness, the Shetland and Orkney islands, and 

 other parts were coloured according to the work of Murchison. A larger 

 Geological Map of Scotland, by A. Geikie, was published in 1876. 



Now, the Geological Survey has mapped in detail the southern 

 half of Scotland, and a large part of the central and north-western 

 Highlands, while Professor Lapworth, Professor Judd, and others, 

 have contributed largely to our knowledge of particular strata, so that 

 it is appropriate that a new and larger map should picture the 

 progress that has been made. This map is accompanied by Explana- 

 tory Notes (pp. 23), in which is given a concise account of the leading 

 features in Scottish Geology. 



In the older map two colours were used to denote Laurentian 

 and Cambrian rocks. Now the Pre-cambrian rocks are taken (in 

 the Explanatory Notes) to include Lewisian, Dalradian, and Torri- 

 donian ; and no less than 10 coloured tablets serve to indicate divisions 

 that can be made in the Metamorphic rocks of the Highlands 

 (grouped as Dalradian), and two tablets include other divisions of 

 Serpentine and Lewisian Gneiss. The relations of the " Eastern or 

 younger Schists " (to which the name Dalradian has been applied by 

 Sir A. Geikie) are still so obscure that they cannot be placed in a 

 definite position in the stratigraphlcal series. The Torridon Sand- 

 stone, now known to be Pre-cambrian, is followed unconformably by 

 the Cambrian strata ; and these again can nowhere be traced in 

 sequence with the Silurian rocks, of which the lowest portion is 

 correlated with the Arenig group. Succeeding strata of Old Red 

 Sandstone, Carboniferous, Permian, Triassic, Jurassic, and Cre- 

 taceous are duly indicated ; there being 19 coloured tablets to repre- 

 sent the main divisions from the Torridon Sandstone to the top of 

 the Mesozoic strata. Four other tablets serve to indicate the 

 Tertiary and Post-tertiary deposits, and eight tablets are given to 

 various Igneous rocks. 



The scale of the map is 10 miles to an inch, so that in size it is a 

 little over 2 ft. wide by 2 ft. 6 in. in length; and it should be mentioned 

 that the Orkney and Shetland Isles, and also the adjoining tracts of 

 Cumberland and Northumberland, and a small part of the north-east 

 of Ireland, are colotired geologically. There are likewise seven 

 longitudinal sections. Altogether, the map is an excellent one, and 

 the modest price of six shillings will ensure for it a wide circulation. 



