568 



NATURE 



{Oct. 26, 1876 



Lower Carboniferous group with the sandstones answering 

 to the same description that rest unconformably on the 

 Lower Old Red of Forfarshire is regarded as established 

 notwithstanding the occurrence in their associated lime- 

 stones (in Nithsdale and elsewhere) of carboniferous lime- 

 stone fossils. This bold course may be taken as a protest, 

 on Prof Geikie's part, that such questions are not to be 

 settled on palaeontological grounds alone. 



Along the southern edge of the Grampians the present 

 map shows that the fault which for a long distance 

 separates the Silurian slates from the Old Red Sandstones 

 and conglomerates, runs all the way from Strathearn to 

 Glen Esk (a distance of about fifty miles), within the old 

 red area. Here then we have a noble exposure of the 

 base of that formation abutting against its Silurian shores ; 

 and we learn from its interbedded igneous rocks and 

 trappean conglomerates, that even thus early, volcanic 

 activity had set in on the margin of the Highlands. As 

 far north as the Orkney Isles, the sub-divisions of the old 

 red have been re-arranged, Prof. Geikie having himself 

 observed the unconformability of the red sandstones 

 (Upper Old Red) on the Caithness Flags on the west 

 coast of Hoy. 



In the Silurian Highlands many of the'chief folds and 

 variations of the metamorphic rocks are clearly indicated, 

 and old mineralogical observations are corrected, largely 

 through Prof. Geikie's own frequent traverses. The 

 Laurentian and Cambrian rocks of the north-west coasts 

 and islands seem to have sufifered no changes since the 

 publication of the sketch-map, except slight rectifications 

 of boundaries required by the larger scale. 



Much light has been thrown within the last few years 

 on the mesozoic and tertiary rocks of the Moray Firth, 

 Skye, Mull, and Arran, and this new information has 

 been skilfully embodied in the map. Besides his own 

 work in this department Prof. Geikie justly acknowledges 

 his obligations to Ramsay, Judd, Bryce, and Zirkel. 



It has been found possible to indicate at least two 

 phases of the Glacial epoch, that of the main extension 

 of the ice-sheet, and that of the later local glaciers. Of 

 the direction of the ice-flow during the former phase an 

 idea may be gathered from the arrows denoting observed 

 glacial striae, while the moraines of the later period are 

 shown by a neat system of stippling. Both in the High- 

 lands and the Southern Uplands the number of valleys 

 containing glaciers seems to have been very great. Scot- 

 land must have been a magnificent country for tourists in 

 these pre-historic times. 



In conclusion, we need only say that geological 

 students have now in their hands a portable map 

 that will supply them with much valuable information, 

 and with suggestions equally valuable with regard to 

 problems awaiting solution. Prof. Geikie is to be con- 

 gratulated on the successful completion of a task for 

 which he was peculiarly qualified, both by his position as 

 Director of the Survey and by his thorough acquaintance 

 with the minutest details of Scottish geology. R. L. J. 



OUR BOOK SHELF 

 Botanical Reminiscences in British Guiana. By Richard. 



Schomburgk. (Adelaide : 1876.) 

 The able and indefatigable superintendent of the Botanic 

 Garden at Adelaide was appointed, many years since, by 



the Prussian Government, naturalist to the Boundary 

 Expedition to British Guiana entrusted by the British 

 Government to his late broiher, Sir Robert Schomburgk ; 

 and in this small, but extremely interesting volume, he 

 gives an account of that " El Dorado," as he appropriately 

 terms it, of tropical botany. Dr. Schomburgk's descrip- 

 tion of the floral treasures of the district, and especially 

 of the Roraima mountains, where forms of the most won- 

 derful beauty unfold themselves at every step, and 

 undergo the most rapid transformations with every 

 change of altitude, are enough to make the mouths of 

 stay-at-home botanists water. The expedition was not, 

 however, without its difficulties and dangers. On the 

 Roraima mountain, which rises to the height of about 

 8,000 feet a few degrees north of the equator, the humidity 

 of the air was so great that the artist who accompanied 

 the expedition found sketching on the saturated paper 

 impossible, while the powder in a loaded gun became 

 changed, in a few hours, into a greasy mass. The ascent 

 of the upper part of this mountain chain was a feat 

 worthy of the most enterprising members of the Alpine 

 Club. A perpendicular wall of sandstone rock, 500 feet in 

 height, had to be scaled by the entire party by means of 

 the net-work of climbing plants which covered it ; the 

 giving way of a single root would have involved one or 

 more of the party in certain death. The account of 

 this expedition dissipates the idea that food is every- 

 where abundant within the tropics, even in thickly- 

 wooded and well-watered countries. For days together 

 the party saw no mammals or birds, and were reduced to 

 the point of starvation from the absence of all esculent 

 vegetables. One observation of Dr. Schomburgk's is im- 

 portant, as being at variance with our modern theories 

 regarding the purpose of the bright coloration of flowers. 

 Near the summit of the mountain range, where the earth 

 was carpeted with flowers of gigantic size, of the greatest 

 brilliancy of colour and delicacy of scent, " it appeared 

 almost as if this boundless abundance of flowers com- 

 pensated for the total absence of animal life ; all was 

 wrapt in deep solemnity ; not even a gorgeous humming- 

 bird or a graceful honey-sucker was seen fluttering 

 amongst the flowers." Has this singular observation 

 been confirmed by other American travellers ? Dr. 

 Schomburgk's observations were not entirely confined to 

 the flora of the country. While stopping at a Warrau 

 settlement on the Barima river, he records the curious 

 fact of a young woman nursing at one breast a child and 

 at the other a young monkey ; and states furthermore, 

 that he has seen, " with the exception of the carnivorous, 

 all kinds of animals suckled and reared by Indian 

 women." While ascending the Roraima mountains his 

 attention was arrested by rows of Indian hieroglyphic 

 writing on the sandstone rock, roughly representing, for 

 the most part, the human form, kaimans, and snakes. 

 There is one defect in this interesting volume, which 

 should have been rectified before going to press. Either 

 from want of exact knowledge of the language on the 

 part of the author, or from the deficiencies of a colonial 

 printing-office, many of the sentences are so maccurately 

 worded as to be barely intelligible. A. W. B. 



LETTERS TO THE EDITOR 



\The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the ivriters of, rejected manuscHpts. 

 No notice is taken of ano7tynious cotiwutnications,^ 



On the word " Force " 



In the Times' report (Sept. 9, 1876) of Prof. Tait's lecture at 

 Glasgow on Force, it is stated that " the lecturer showed how 

 the incorrect physical ideas of Leibnitz, and some of his fol- 

 lowers, had introduced the terms vis viva, vis mortua, and tHs 

 acceleratrix," and that these terms were found also in English 

 works. tVe may add that, until quite lately, Cambridge treatises 



, 



