NA TURE 



[Junk 4, 1S96 



the kathode disc. The tul)-> on which the observation was made 

 has been cracked, and now ceases to give the restdt ; nor is he 

 able to impart rola'ion in one direction only by familiar 

 mechanical means that could have existed in the tube. 



From across the Atlantic, correspondents of some of the daily 

 newspapers have sent vague reports of several developments of 

 Riintgen ray work. By coating the inside of a Crookes' lube 

 with fluorescent crystals, Mr. Edison is stated to have produced 

 an electric lamp in which "all the energy which in an incan- 

 descent lamp is lost in heat is turned into light. One of the new 

 lam|)S of only four-candle power is said to give a light equal to 

 that obtained by the usual sixteen-candle power incandescent 

 lamp." 



A report from the electrical laboratory of the State Univer- 

 sity of Missouri states that experiment shows that Riintgen rays 

 kill the bacilli of diphtheria. Two guinea pigs were inoculated 

 with a culture of diphtheria. One of them was exposed for four 

 hours to these rays, and showed no signs of diphtheria. The 

 other died within twenty-eight hours, and the post-mortem 

 examination showed that diphtheria was the cause of death. It 

 hardly needs pointing out, however, that this evidence is not 

 sufficient to justify the conclusion. 



In Cosmos, M. R. P. Leray gives the first portion of an article 

 on kathodic rays and the kinetic theories of their nature. The 

 writer points out that although recent investigations have cast 

 some doubts on Crookes' original "radiant matter" thejry, no 

 satisfactory alternative theory has been suggested. M. Poincare 

 has propounded the hypothesis that the phenomenon is produced 

 like a luminous phenomenon, but, as he remarks, this is a very 

 strange form of light. M. Leray considers that this substitution 

 of the ether for radiant matter, while failing to account for the 

 earlier experimental results, affords no explanation of recent dis- 

 coveries. The kinetic theory should not be abandoned, simply 

 because it does not account for all the observed phenomena, 

 until some theory has been suggested that better accords with 

 lact. 



Finally, in the Naturwissenschaftliche Wochenschrift^ Prof 

 B. R. Borggreve offers a theory of the existence of Rontgen rays, 

 and considers particularly the relation of Rbntgen's discovery to 

 Le Bon's so-called "dark light." 



THE RELIEF OF THE EARTH'S CRUST. 

 pROF. HERMANN WAGNER, of Gottingen, one of the 

 ■^ best-known geographers and statisticians of Germany, has 

 recently published in GerlaiiiVs Beilrii!;e :iir Geophysik, a 

 critical study ' of a somewhat exceptional kind. The moral of 

 the criticism is that the agreement of the final results of a pro- 

 longed series of calculations is no proof of the correctness of the 

 individual stages of the work, and the application is that no 

 elaborate series of calculations should be built upon until every 

 step has stood the test of independent verification. One is 

 tempted to suppose that all scientific workers believed in these 

 principles, and that the steam-hammer strokes of Prof. Wagner's 

 ponderous criticism are really more valuable in forging a firmer 

 structure of fact, than for the sparks of proverbial philosophy 

 elicited by battering the woik of pioneers. The solid outcome 

 of the investigation is the most detailed calculation yet arrived 

 at of the area and volume of the portions of the earth's crust 

 above and below sea-level, leading to a new and interesting 

 division of the surface of the lithosphere into regions of special 

 morphological character. Although this comes last in the dis- 

 cussion, we prefer to place it first in the appreciation, because 

 constructive work is always more pleasing to contemplate than 

 destructive efforts, and because those who, like myself, have 

 been somewhat severely handled by Prof. Wagner, will (irobably 

 be most willing to acknowledge the superior accuracy of his 

 results. 



The question of the completeness of the data from which 

 these results are derived, and their fitness for such minute treat- 

 ment, I shall consider later. 



By means of the hypsographic curve connecting elevations and 

 percentages of area (previously employed by Penck in his dis- 

 cussion of Murray's data) derived from measurements of height, 



1 " Arc-vl und mittlere Erhetiung der I,aiidfl:ichen sowie der Erdkruste. 

 Eine kritisdic .Studic insbe.sondcre iiber deji .\nwendung*bcreich der 

 Simpson'sche Formel " Von Hermann VVasner. Garland s IScitriigc znr 

 Geophysik\ II. liand, 2-4 Heft (1895), pp. 667-772. 



NO. 1388, vol.. 54] 



depth and area of land and water, the surface of the lithosphere 

 is divided by Wagner into five regions in place of the three sug- 

 gested by I)r. John Murray, and hitherto accepted by most 

 physical geographers. The five are as follows. The Ciilntina'- 

 ingArca of the earth's crust, occuping 6 per cent, of the surface, 

 and lying altogether above 1000 metres, with a mean height of 

 2200 metres (or 7200 feet) above the sea. The Contiiicniai 

 Plakau, occupying all the surface from the 1000 metre contour- 

 line of elevation to the 200 metre contour-line of depth, i.e. to- 

 the margin of the shallow sea-border or continental shelf. It 

 comprises 28 '3 per cent, of the surface, and has a mean elevation 

 of 250 metres (or 800 feet) above the sea. The Conliiieii.'at 

 S/ope, from a depth of 200 metres to 2300 below sea-level, covers 

 9 per cent, of the earth's .surface, and has a mean depth of 1300' 

 metres (or 4300 feet). The Oceanic Plateau, between the depths 

 of 2300 and 5000 metres, occupies no less than 537 per cent, of 

 the surface, and has a mean depth of 4100 metres (or 13,500 

 feet). Finally the Depressed Area, deeper than 5000 metres, is 

 assumed to occupy 3 per cent, of the surface, with a mean 

 depth of 6000 metres (say 20,cxX) feet). In this classification of 

 regions the coast-line is ignored, the abrupt change of slope ni: 

 200 metres (or r.ather the familiar lOO-fathom line of our charts/ 

 being rightly given the greatest weight in a hypsographic study. 

 The mean level of the surface of the earth's crust is placed by 

 these calculations at a depth of 2300 metres, or 7500 feet 

 below actual sea-level. The area of the continental-block, or 

 region above the mean level of the crust, is found to be 43'3 per 

 cent. of the surface, leaving 567 percent for thedeeper region, in- 

 stead of the 50 per cent, to which my first estimate of mean-sphere- 

 level from Murray's data pointed. Although I suggested in ApriF 

 1890, the restriction of .Murray's term Aby.smal Area to the ocean- 

 floor below mean-sphere-level (instead of including everything 

 below 1000 fathoms), and to class the whole slope up to sea- 

 level as the Transitional Area, keeping the term Coniinentaf 

 Area for the land ; I gladly recognise the importance of Wagner's 

 new division into five zones, as shown on the accompanying 

 curve (p. 113). Two further subdivisions might be a|iproprialely 

 introduced- the Fiat lands heXow 200 metres rf elevation, an<l 

 the Coiilineiital Shelf, or shallow sea above 200 metres of depth. 

 From the anthropogeographical point of view, the.se are the most 

 important regions of the globe. The height of 200 metres above 

 actual sea-level corresponds by Wagner's showing to the meaa 

 level of the physical globe (lithosphere and hjdrosphere), and is 

 thus as fitted to be a limit as is the line of mean-sphere-level 

 itself. 



The total area of land is worked out at 28 '3 per cent., and that 

 of sea as 717 of the earth's surface, certain assumptions being 

 made for the unknown polar regions. The ratio of land to 

 water surface is thus i : 2 '54. Other interesting levels are that 

 of the mean height of the land 700 metres (or 2300 feet) above 

 actual sea-level ; and of the condensation spheroid, i.e. the 

 physical globe if the water were condensed to the density of the 

 rocks of the crust, 1300 metres (or 4260 feet) below present sea- 

 level. 



While Prof W.igner has sought to give more exactness to the 

 calculations on which our knowledge of the forms of the earth's 

 crust depends, he has shown little sympathy with any sugges- 

 tions towards an explanation of terrestrial relief. We have not 

 space at present to consider his criticism of the remarkable re- 

 lations between the various natural divisions of the crust involv- 

 ing the ratio of the densities and volumes of land and sea pointed 

 out by Romieux in December 1S90. Similarly the strictures on 

 Penck's " Morphologic der Erdoberflache " may be left for that 

 distinguished physical geographer to treat personally. 



The problem of finding the areas and volumes of the portions 

 of the earth's crust above water or covered by water, and .so of 

 arriving at some knowledge of the true forms of the earth's 

 crust, has been attacked by several physical geographers during 

 the last twelve years. Prof. De Lapparent, in 1883, was the first 

 to repeat Humboldt's attempts in this direction. Dr. John 

 Murray, in 1888, published a very elaborate calculation based on 

 contoured maps specially prepared by Bartholomew on Lam- 

 bert's equivalent"projection on the scale of i : 45,ooo,cX)0. Thii 

 work was criticised on publication by Prof I'enck and Dr. .-\. 

 Supan, but attained wide acce]Mance. Prof. Wagner, for the 

 purposes of his well-known statistical annual, " Die Bevolke- 

 rung der Erde," had collected the best estimates of the areas 

 of the various continents and countries, and has caused correc- 

 tions and new measurements to be made from time to time. 

 All this work may be said to depend on the measurement of 



