NATURE 



[May 7, 1908 



(2) Gauging stations ; methods adopted for measur- 

 ing the discharge of streams. 



(3) Pluviometry, nivometry, and glacial studies. 



(4) Planimetry ; surface measurement of basins. 



(5) Levelling ; determination of slope and fall. 



(6) Publication of results. 



The records are very full and complete. They 

 abound in instances of local difficulties and the manner 

 in which these were overcome. The work was carried 

 out under the joint direction of M. de la Brosse and 

 M. Tavernier. The former gentleman concerned him- 

 self more particularly with the basins of the Arve and 

 the Isere, and the latter with the basins of the Durance 

 and the Var. 



There are a large number of appendices dealing 

 with various matters of special interest, including some 

 practical directions in the matter of gauge measure- 

 ment, a note on the theory of screw- calibration, a pro- 

 visional estimate of the value of the hydraulic forces, a 

 typical hydrological study of a mountain basin, and 

 other cognate matters of importance. 



The theoretical and mathematical investigations are 

 of an extended and detailed character, and the volume 

 forms a thoroughly complete and valuable guide for 

 those who are engaged in hydrographical studies and 

 experiments. A number of interesting photographs 

 are reproduced, showing the actual operation of 

 gauging as carried out at several places, and illustrat- 

 ing in a most effective manner the expedients described 

 in the text for dealing with particularly difficult and 

 almost inaccessible stations. 



It is recorded that a good deal of very useful assist- 

 ance was derived from voluntary workers, including 

 those at power stations and industrial depots. Help 

 was also forthcoming from officers at military posts 

 and from the staff of the conservators of waters and 

 forests. Aid was rendered, too, by meteorological and 

 geological departments, municipal and vicinal ad- 

 ministrations, and by railway companies, notably the 

 Paris-Lyon-Mediterranee. The coordination and in- 

 struction of all these various agencies, spread over an 

 extended area, involved much care and attention. 



The second volume is devoted almost entirely to a 

 numerical record of the results of the work.' It abounds 

 in figures and data systematically collated and ar- 

 ranged, so as to be of immense value for reference 

 purposes. It also includes a series of excellent maps 

 of the various basins printed in colours, showing the 

 subsidiarir watersheds, and indicating the positions of 

 the stations of observation. .Altogether, the volumes 

 are replete with information, and form a striking testi- 

 monial to the value and national utility of the Service 

 d'Etudes des grandes Forces hydrauliques. 



SUBTERRANEAN STUDIES. 

 L'Evolution soiiterraine. By E. A. Martel. Pp. 388; 

 with 80 figures. (Paris : Ernest Flammarion, 1908.) 

 Price 3.50 francs. 



IN France, the fascinating study of caverns — or, as 

 it is now the fashion to call it, spelaeology — has 

 risen greatly in popular favour during the last twenty 

 years, mainly through the energy and enthusiasm of 

 NO. 2010, VOL. 78] 



M. Martel, one of the editors of La Nature. The 

 scope of spelaeology, in the course of its recent de- 

 velopment, has become gradually enlarged until it now 

 touches at one point or another almost the entire 

 circle of the sciences. The work before us, which 

 forms a volume of Dr. Gustave Le Bon's " Biblio- 

 theque de Philosophie scientifique," extends, however, 

 beyond the mere study of caves, though this forms its 

 main theme. From caverns the author passes to the 

 general phenomena of the underground world, and 

 seeks to show how their study has a bearing on nearly 

 all branches of knowledge, especially on the doctrine 

 of evolution. The range of the work consequently 

 comes to be extremely wide. Where the programme 

 set before the writer is so ambitious, no reasonable 

 reader can expect to find it worked out with thorough- 

 ness. Brevity often becomes imperative. The wonder 

 is not that many of the subjects are touched with 

 only a ligiit hand ; the wonder is rather that it has 

 been found possible to crowd so much into a volume 

 of such limited size. 



Scattered through M. Martel 's pages are many 

 suggestions which seem to call for remark. Thus, 

 with regard to the planes of rupture in the earth's 

 crust, he suggests that the term " joint " should be 

 limited to planes of stratification, whilst those fissures 

 which run vertically or obliquely, and in stratified 

 Irocks across the bedding, should be called " diaclases " 

 ■ — one of the terms introduced by Daubr^e in his 

 system of nomenclature for divisional planes. No 

 doubt it would be convenient to have some short word 

 for a plane of bedding, but it will certainly require 

 much persuasion to induce an English geologist to 

 call it a joint, for this happens to be just the term 

 that he is in the habit of applying to any plane other 

 than that of stratification. 



Our author does well to insist on the fact that the 

 process of cave-making, so far from being due to a 

 single agent, depends in most cases partly on 

 mechanical erosion and partly on chemical corrosion. 

 Which of the two processes is the more important is 

 determined to a large extent by the character of the 

 rock to be hollowed out. Moreover, the formation of 

 these subterranean hollows has not been limited, as 

 some Continental writers have supposed, to any parti- 

 cular geological epoch. 



On the question of the supposed desiccation of the 

 earth — a subject on which so much has been written — 

 M. Martel holds very pronounced views. Whilst some 

 writers who admit the progressive diminution of the 

 earth's superficial waters believe that it proceeds too 

 slowly to be recognised in historic time, our author 

 holds that abundant evidence of the change may be 

 cited within the range of human history. On the 

 other hand, a compensating 'action may come into 

 play if it be true, according to an opinion that has 

 recently been gaining ground in certain quarters, that 

 much of the water emitted as vapour by volcanoes is 

 derived from the deep-seated magma of which it is an 

 original constituent, so that its emission is a direct 

 contribution to the surface-waters of the globe. 



It was only to be expected that M. Martel would 

 have much of interest to say on his favourite subject 



