302 



NATURE 



[August 25. 1923 



English and French. Its three chief officials arc 

 Sh- J. D. Parry (Great Britain), Admiral l*hafl 

 (Netherlands), and Captain Miillcr (Norway), the first- 

 named being president. It confines itself to hydro- 

 graphy in the strictly nautical sense of the word, and 

 one of its chief objects at present is the international 

 standardisation of practice in relation to many mari- 

 time matters. For example, in relation to charts, 

 among the questions which arise are those of the 

 type of projection, the scale, the choice of imits for 

 depth and distance, the mode of delineation of sound- 

 ings, the symbols and abbreviations, and the geo- 

 graphical names to be used. Lists of lights, sailing 

 directions, and distance tables are other matters on 

 which more uniformity and co-operation would be 

 advantageous. It may be noted that most countries 

 now use metric units for depth, Japan being one of 

 the latest formally to adopt this system, though it 

 has not yet actually introduced it. Great Britain 

 and America are now the only States which exclu- 

 sively use the fathom and foot, but the change to 



the metric system is one which they are as yet un- 

 willing to make, because of the great difficafty and 

 cost of altering the coppwr plates from which are 

 printed the exceptionally large number of charts 

 which these countries produce. 



The Bureau has recently started a journal, the 

 Hydrographic Jieview, of which the first number 

 appeared in March last. It is bilingual, all its 

 contents being duplicated in F2nglish and French, on 

 opposite pages. A large part of the first issue is 

 devoted to the history of the inception of il>i- r^ircau, 

 and other official matters. The chief or; :< les 



consi-st of two reports on aerial ph<n ... v as 

 applied by the French and Netherlands services to 

 hydrographic surveying and the discovery of shoals 

 and covered rocks. There is also a discussion of the 

 visibility of hghts, considering the chances which a 

 sailor has of sighting a given light in different circum- 

 stances at various distances, and a brief report on 

 echo sounding as practised by the United States 

 hydrographic department. 



The Age of 



CINCE the advent of our knowledge of radio- 

 *^ active processes, the old controversy over the 

 age of the earth has been revived, and although 

 there is now a marked change of opinion in favour of 

 the longer estimates, it remains unfortunately true 

 that there still appear to be tantalising discrepancies 

 between the results from different methods. These 

 discrepancies may be mitigated or exaggerated by 

 special pleading, but they still stand in the way of 

 an unequivocal settlement of the problem. 



Twenty years ago various attempts were made to 

 squeeze geological history into the narrow limits 

 imposed by Kelvin and Tait. The discovery of 

 radioactivity, and more recent advances in the study 

 of stars and tidal friction, have destroyed the value 

 of the older physical evidence, leaving various geolo- 

 gists committed to what are now seen to be absurdly 

 low figures. In the last decade the geological methods 

 have in turn been widely criticised, and the present 

 tendency is greatly to extend the estimates formerly 

 favoured. AH the methods adopted depend on the 

 rate of processes at present in operation. In order 

 that the different lines of evidence should converge, it 

 is necessary to suppose either that the rates of geo- 

 logical processes are at present too high, or that 

 those of radioactive processes are too low, to justify 

 integration over the whole duration of geological 

 time. 



In the symposium under consideration, held in 

 Philadelphia on April 22 last year, the chief feature 

 of interest is Chamberlin's spirited attempt to show 

 how the geological estimates may be brought into 

 harmony with the revised deductions from radio- 

 activity and astronomy. The period required for the 

 deposition of the whole of the sedimentary column or 

 for the accumulation of salt in the oceans is easily 

 arrived at from existing data on the assumption that 

 present rates provide a characteristic average. There 

 is now little doubt that this assumption is deceptive, 

 and it certainly can no longer be admitted. De 

 Geer's work on the yearly deposits from glacial 

 waters in Sweden, though an exceptional case, 

 suggests to Chamberlin a Glacial epoch fully twenty 

 times as long as that assigned by the old methods. 

 He further expresses the conviction that breaks in the 

 continuity of more normal sediments, the time-values 



• From the Geological View-point. By T. C. Chamberlin. From the 

 Paleontological View-point. By J. M. Clarke. From the Point of View of 

 Astronomy. By E. W. Brown. The Radioactive Point of View. By W 

 Duane. (Proc. Amer. Phil. Soc., vol. Ixi., No. 4, pp. 247-88 1022 

 Philadelphia.) ^*^ * ' ^ 



NO. 2808, VOL. I 12] 



the Earth.i 



of which are best judged by comparison of the 

 faunas above and below, must, when finally inter- 

 preted, greatly extend the simple arithmetical 

 estimates. It has frequently been shown how 

 denudation and deposition must be quickened up by 

 human activities, and the effects of cultivation and 

 excavation have been ably analysed by Dr. Sherlock 

 in his recent " Man as a Geological Agent." Existing 

 conditions also naturally favour a high rate of denuda- 

 tion, since continental elevation and breadth are 

 both exceptional, and to these may be added the 

 further consideration that broad areas are strewn 

 with easily removable glacial deposits. So variable 

 are the factors involved that there is no means of 

 arriving at average rates which would properly 

 include long periods of sea-transgression and Isase- 

 levelling, periods when denudation was brought 

 almost to a standstill. 



The validity of the method based on the accumula- 

 tion of salt in the oceans depends partly on the rate 

 at which the present streams are carrying sodium 

 down to the sea — a rate which must be too high for 

 reasons already mentioned — and partly on the 

 irreversibility of the process. It has, of course, been 

 generally recognised that sodium returns to the land 

 in interstitial solutions held by sediments and as 

 wind-borne salt, but other possibilities have been 

 less emphasised. Actually it is found that the data 

 used are inconsistent among themselves unless other 

 cyclic processes are involved. The most serious dis- 

 crepancy is found in the ratio of sodium to chlorine, 

 which in igneous rocks is about 30 : i and in the 

 oceans about i : i-8. When volcanic exhalations are 

 taken into consideration this enormous difference is 

 reduced but by no means wiped out. Clarke and 

 Washington have given figures which include the 

 whole of the atmosphere and hydrosphere, and the 

 discrepancy still remains as high as 20 : i. 



There can be only one explanation : that chloridised 

 sodium plays a far greater part in cyclic action than 

 has yet been detected. In the case of p>otassium such 

 circulation is all-important and is effected by its 

 greater retention by muds and soils. Dr. Milton 

 Whitney writes, " Ocean shore deposits would un- 

 doubtedly absorb XaCl up to the point where the 

 colloids were in equilibrium with sea water," but as to 

 the relative efficiency of this and analogous processes 

 there is still no exact knowledge. The sodium 

 method is thus, as Chamberlin says, " not yet ready 

 to render a verdict." As to the sedimentation method. 



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