6/0 



NA TURE 



[October 31, 190; 



lives of others. The new medal will be of two classes, 

 which are to be designated the Edward medal of the first 

 class and the Edward medal of the second class. The 

 ribbon will be dark blue with a narrow yellow stripe on 

 either side. 



The Engiiucriiig Magazine for October is a special 

 number of great interest, devoted exclusively to mining. 

 There are articles on the copper situation in the United 

 States, the production of gold, the mechanical engineering 

 of the mine, the manufacture of steel and wrought iron, 

 asbestos, excavations for the foundations of a modern tall 

 building, electrometallurgical progress, steam production 

 from the cheaper grades of anthracite, underground work- 

 ings in New York City, and the unwatering of mines in 

 the anthracite region. .^11 these articles are written by 

 leading authorities and are admirably illustrated, and the 

 whole forms a trustworthy review of current practice. 



At the first meeting of the new session of the Institu- 

 tion of Mechanical Engineers, Prof. Bertram Hopkinson 

 read an important paper on the indicated power and 

 mechanical efficiency of the gas engine, describing an 

 investigation made with the object of finding whether the 

 indicator power of the gas engine does, in fact, vary so 

 much and is so difficult of determination as the report of 

 the committee of the Institution of Civil Engineers on 

 the efficiency of internal-combustion engines suggests. The 

 conclusions reached were as follows : — (i) If precautions 

 are taken to keep the pressure of the gas supply constant, 

 the diagrams given by the engine are remarkably regular, 

 and whether the engine be missing ignitions or not, it is 

 possible, by the use of a sufficiently accurate indicator, to 

 obtain the indicated power from diagrams within i per 

 cent, or 2 per cent. It seems probable that the difficulty 

 experienced by the committee was due either to the essential 

 defects, for this purpose, of the ordinary form of indicator, 

 or to casual variations in the gas supply per suction due 

 perhaps to variation in the gas pressure at the engine. 

 (2) The difference between indicated horse-power and brake 

 horse-power is rather less than the horse-power at no load 

 under the same conditions of lubrication, mainly because 

 of the difference in the power absorbed in pumping. In 

 the particular engine tested by Prof. Hopkinson the error 

 from this cause in obtaining the indicated power would 

 amount to about 5 per cent. The friction is substantially 

 constant from no load to full load, provided that the 

 temperature of the cylinder walls is kept the same, but 

 the influence of temperature is very great. 



The current number of the Quarterly Review includes 

 an important article, by Mr. Urquhart A. Forbes, on the 

 water supply of the United Kingdom. The importance of 

 treating water supply on broad lines was pointed out by 

 the 1869 Commission on Water Supply, when the adop- 

 tion of the watershed area as the administrative unit for 

 water supply was recommended. Since the water supply 

 for purposes of navigation is derived from the various 

 watersheds traversed by canals and river navigations, it 

 is desirable that the authority in each watershed should 

 be empowered to exercise some control over canal com- 

 panies and river trustees with respect to the amount of 

 water to be abstracted from it. Such watershed boards 

 with the powers indicated would be able to carry out the 

 scientific regulation of all water from its first arrival as 

 r.iin to its disappearance in the ocean. It has been sug- 

 gested that the staff of the central authority, which would 

 be a department under the Local Government Board, 

 would, in addition to the administrative head, comprise 

 (i) an engineer and assistants, with a special knowledge 



NO. 1983, VOL. 76] 



of geology and water supply, charged with the duty of 

 collecting and digesting for use all the facts requisite for 

 the scientific treatment of our water system ; (2) {i bacterio- 

 logist and a chemist, with a special knowledge of the 

 bacteriology and chemistry of sewage, trade effluents, and 

 water supply, who should be provided with a laboratory 

 for experiments ; (3) a staff of inspectors for carrying out 

 its supervisory work with respect to both pollution and 

 waste of water. In addition to the facilities it would 

 provide for the treatment of our water system on scientific 

 principles, the establishment of a central water depart- 

 ment offers the best means of restoring order in the present 

 chaotic condition of things. 



The great changes wrought by the eruption of April, 

 1906, necessitated a re-survey of Mount Vesuvius, which 

 has been effected by the Italian Military Geographical 

 Institute. The extreme height of the mountain was deter- 

 mined as 1223 metres above sea-level, as compared with 

 1335 metres before the eruption ; the height of the crater 

 rim has become more irregular, dropping to only 1103 

 metres on the E.N.E., with a diameter of 725 metres from 

 N.N.E. to S.S.W., and 645 metres from N.W. to S.E. 

 At lower levels the contours have everywhere been en- 

 larged from those of the survey in 1900, and in the Atrio 

 del Cavallo and Valle dell'Inferno the depression has been 

 filled up to the extent of from 5 metres to 5° metres. 



In travelling by rail, or still better by steamer, from 

 Lyons to .Avignon, a marked narrowing of the Rhone 

 Valley is noticed after Valence, between the pre-.\lps of 

 Dauphin^ on the left and the singular dark ridge of 

 Coirons on the right. This easterly spur of the central 

 massif of France is capped by a thick sheet of basalt, 

 which affords a striking instance of inversion of topo- 

 graphy. There is no doubt that, at the close of the 

 Miocene, when the molten rock issued from a vent located 

 near Mount Gerbicr des Jones, it followed one of the 

 channels of the river system of that period. Since that 

 time the eastern border of the central massif (C^vennes) 

 has been subjected to strong erosion, increased by the 

 subsidence of the lower part of the Rhone Valley, and the 

 consequent lowering of the base-level. The surrounding 

 Cretaceous and Upper Jurassic limestones have been easily 

 worn down and reduced to gentle slopes. The basaltic 

 flow, about thirteen miles in length and three miles wide, 

 resisted much more successfully the subaerial disinte- 

 gration. In consequence of this very unequal weathering, 

 what was once a valley is now a long ridge standing 

 2200 feet above the level of the Rhone. The history of 

 the Coirons may be compared to that of the Scuir of 

 Eigg in western Scotland. Unfortunately, a portion of 

 the sheet of lava of Coirons rests upon the Oxfordian, 

 easily undermined by the head-waters of the lateral 

 torrents ; the edges of the volcanic table are liable to 

 break away and to creep down the slopes upon the clayey 

 substratum. The landslip which occurred on October 11 

 above Moulin-Artige is only an episode in this process of 

 slow undermining, which has reduced the formerly con- 

 tinuous basaltic plateau to the shape of a fish-bone. As 

 a consequence of the torrential rains which occurred in 

 southern France during the first part of October, nearly 

 one million cubic metres of rocks has moved a distance of 

 900 metres, threatening to block a valley and to form a 

 lake. Such incidents are bound to occur again on both 

 sides of the Coirons, and the suggested re-affoi'esting of 

 the district will tend to diminish, but not to prevent, all 

 future danger. Perhaps it would be wise to restrict the 

 construction of villages to safer ground. 



