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KNOWLEDGE. 



[April 1, 1897. 



Dr. T. K. Eose, in Xtitior, March lltb, describes the 

 methods of gold extraction by the Tvet process. Although 

 rapid advances have been made in the science of chemistry, 

 only about one-tenth of the total output of gold is produced 

 by that means. The chief processes of wet extraction are 

 by means of mercury, chlorine, and cyanide of potassium. 

 The mercury process is very imperfect, owing to minute 

 particles of gold remaining undissolved, and also because 

 of the action of mercra-y on sulphides of iron, antimony, 

 and arsenic, which are hardly ever absent from gold ores. 

 The chlorination process is more satisfactory, but is rather 

 expensive. When sulphides are present, preliminary 

 roasting is necessary. In some cases chlorine gas is 

 employed, but nowadays strong aqueous solutions of the 

 gas are found to act more rapidly. The disadvantage of 

 this process is assignable to the preliminai-y roasting of 

 the ore. The best process of all is the MacArthur and 

 Forrest cyanide method, which obviates preliminary 

 roasting of the ore. This method of extraction is based 

 on the solubility of gold in potassium cyanide, and the 

 subsequent separation of the gold by means of zinc. 

 Sulmau and Teed propose to add cyanogen bromide 

 to the potassium cyanide, but this method has not 

 been carried out on a large scale up to the present. 

 Siemens and Hulske propose to precipitate the gold 

 from cyanide solutions by electro-deposition, but this 

 method is costly, because of the large amounts of iron 

 and lead consumed. 



Mr. W. Eagle Clarke, M.B.O.U., sends us an account 

 of the occurrence of the frigate petrel {Pelayodroma marina) 

 on the west side of Scotland. The bird, a female, was 

 captured alive on 1st January of this year, by the margin 

 of a stream on the west side of the Island of Colonsay. 

 Having been forwarded in the flesh to Edinburgh and 

 identified by Mr. Clarke, it is now in the Scottish National 

 Collection, in the Museum of Science and Art in that city. 

 The closing week of December last was remarkable for a 

 succession of south-westerly gales. This is the second 

 recorded occurrence of this petrel in European seas ; and 

 it is interesting to note that the first record was also for 

 the west coast of Britain, namely, at Walney Island, in 

 Morecambe Bay, where a specimen was washed ashore 

 dead in November, 1800. The frigate petrel has a wide 

 range in the southern hemisphere, and it was found 

 breeding in great numbers on the islands off South-Western 

 Australia by Gould's collector, Gilbert. Prior to November, 

 1890, the most northerly point reached by this species was 

 the Canary Isles, where it has been identified on several 

 occasions. 



At a recent meeting of the Eoyal Botanic Society, the 

 Eev. Prof. Henslow read a paper upon the effects of light 

 on the colouring of plants, a subject on which very little 

 is known. He spoke of the work lately done by Mr. Sorby 

 in this direction with the spectroscope, explaining the 

 efiects of the different light-rays upon plant colours, 

 and showed how all colours were really produced in the 

 green tissue of the leaf. It appears that the learned 

 professor agrees with the theory that yellow is the primary 

 colour. 



Eipples produced on a mercury surface, according to 

 Mr. J. H. Vincent, are invisible to the unaided eye ; but 

 by means of an electric spark photographs of ripples set 

 up in the mercury by a stylus attached to a tuning-fork 

 can be obtained. The phenomena of interference, diffrac- 

 tion, etc., can thus be shown in quite a novel way. 



THE AGE OF MOUNTAINS.-II. 



BRITISH MOUNTAINS. 

 By Professor J. Logan Lobley, F.G.S. 



THE mountains of the British Islands, though their 

 highest summits are but of very moderate eleva- 

 tion when compared with the principal mountain 

 ranges of the globe, are yet of great geological and 

 physiographic interest. Rising, too, sometimes 

 abruptly and steeply from little above the level of the 

 sea, they show their full height, and so give bold and 

 very varied, and in many cases exceedingly beautiful, 

 scenery. Their chief interest, however, lies in the fact 

 that they include perhaps the oldest mountain lands of 

 the world. 



They are very distinctly grouped, each group occupying 

 a well-separated area, and the geology also of each group 

 is, in the main, distinct. Thus the study of British 

 mountains and hills may be simplified by considering 

 them in groups, which may be arranged and designated 

 as follows : — 



England ; Cumbrian, Pennines, Western, Mendips, 

 Oeryneans, Central, South-Eastern. 



Wales; North- Western, Central, Southern. 



Scotland : North- Western, Grampians, Southern. 



Ireland and the Isle of Man : South-Western, South- 

 Eastern, North-Eastern, North-Western, Manx. 



Though space will not allow of the geology of each of 

 these groups being more than very briefly summarized, yet 

 this will, it is hoped, clearly show the very interesting 

 character of the geology of British mountains. 



ENGLAND, 



The mountains of Cumberland, extending into North 

 Lancashire and Westmoreland, constituting the beautiful 

 English Lake District, demand, from their height and the 

 importance of the area they form, first attention. The 

 group attains in Scafell Pike an elevation of three thousand 

 two hundred and twenty-nine feet above the level of the 

 sea. This highest mass, with its surrounding mountains 

 and the peaks and ridges to the east, consists mainly of 

 volcanic rocks, the accumulated ejectamenta of a great 

 volcano possibly as large as yEtna. At Castle Head, close 

 to Keswick, may be seen a mass of Igneous rock that may 

 be the root of the infilling of one of the vents of this great 

 mountain, which existed and was active as a volcano 

 in Lower Silurian times ; and its ruins, which now con- 

 stitute these mountains, may consequently be assigned 

 to that period. On the western side, and on the extreme 

 east of the area, are vast masses of newer, because intrusive, 

 Plutonic granites and syenites. From the great hardness, 

 but still varying hardness, of these Igneous rocks, rugged 

 and precipitous features characterize the area, and give the 

 wildest and most picturesque scenery of the Lake District. 

 The mountains to the north are largely composed of highly 

 metamorphosed Cambrian and Lower Silurian rocks, the 

 drbris of very ancient lands, to which the name Skiddaw 

 Slates is given. The volcanic rocks rest against them, 

 and these again are covered in places, or over-stepped, by 

 the Coniston Limestone series of Bala (Lower Silurian) age. 

 Above the Coniston Limestones, in the south-eastern corner 

 of the district, are Upper Silurian rocks at a high level. 

 Although the Skiddaw Slates were elevated before the 

 volcanic series were accumulated, and therefore in Lower 

 Silurian times, a subsequent depression and still later 

 re-elevation gives to these mountains, including Skiddaw 

 and Saddleback, a date which may be fixed as being between 

 Upper Silurian and Carboniferous times, by the fact tha 



