June 8, 1916]" 



NATURE 



0^0 



Shackleton reached the western coast of South 

 Georgia and climbed over the AUardyce Range 

 to the whaling- station at Stromness Bay. The 

 fact that the island had not been crossed before 

 gives some indication of the difficulty of this 

 feat, which can also be realised from the map 

 and photographs published in Mr. Ferguson's 

 recent memoir on the island (Transactions Roy. 

 Soc. Edinburgh, vol. 1., part iv., 191 5). A 

 relief expedition was at once despatched to Ele- 

 phant Island, but only an eighty-ton vessel was 

 available, and the ice was too thick for her to 

 force a passage to the land. 



The Government has already promised the funds 

 for the larger rescue expedition which had ap- 

 peared necessary. The problem is now much 

 simplified, as the work to be done is definitely 

 known. Elephant Island — in 61° 10' S., about 

 the latitude of the Shetlands — though sometimes 

 surrounded by drift ice, can apparently be reached 

 by a suitable vessel at any season of the year. 

 Relief is obviously wanted urgently. The party 

 on April 24 had only five weeks' provisions, 

 which it can doubtless supplement by penguins 

 and perhaps seals. The name Elephant Island 

 refers to the once-abundant sea-elephants; but 

 as the island is easily accessible they have been 

 practically exterminated there; and Sir Ernest 

 Shackleton's account of the locality where his 

 comrades are camped suggests that it may be a 

 very difficult hunting-ground. 



The larger South Georgia whalers are prob- 

 ably now on their way to Europe, and unless a 

 suitable steamer can be obtained in Argentina 

 or at the Falkland Islands it is to be hoped that 

 the whaler nearest to South Georgia can be 

 promptly intercepted and sent back there, en 

 route for Elephant Island. 



RETURN CURREXTS AND ELECTROLYTIC 

 CORROSIONA 



T^HE two memoirs referred to below are part of 

 ^ the series of valuable contributions which are 

 .being issued by that admirable institution, the 

 U.S. Bureau of Standards, under the able director- 

 ship of Dr. Stratton. 



The publications before us relate to the troubles 

 which arise from the electric return currents that 

 leak through the soil from electric tramways and 

 railways, in consequence of their setting up elec- 

 trolytic corrosion in buried pipes or other metallic 

 objects in the neighbourhood of the tramway or 

 railway lines. This was an acute question in 

 Great Britain as well as in North America some 

 twenty years ago when electric traction was a 

 novelty. But, so far as England is concerned, it 

 long ago ceased to be acute in consequence of the 

 prompt action of the Board of Trade. That often 

 abused body framed a regulation that the maxi- 

 mum allowable voltage drop between any two 



i " U.S. Department of Commerce. Technoloeio Papers of the Bureau ot 

 Standards (Washington)." No. a6, Farth Re.ilsi.-»nce ani it* Relation to 

 Electrolysis, etc. No. 52, Electroly>.i« and its Mitigation. (Wasiington : 

 •Government Printing OfiSce, 1915.) 



2sO. 2432, VOL. 97] 



points of the earthed return-system, near which 

 underground metallic structures are laid, should 

 be limited to seven volts. This limitation, though not 

 an absolute safeguard against stray currents, has 

 practically solved the difficulty; and we never, or 

 seldom, hear any suggestion of electrolytic corro- 

 sion. Were any considerable difference of poten- 

 tial between two points of an earthed return 

 system to be allowed to subsist, that difference of 

 potential would have the result of forcing a frac- 

 tion of the current to leave the return rails at some 

 point of higher potential and to find its way 

 through the soil or other available path, to re- 

 enter the return rails at some point of lower poten- 

 tial, presumably nearer the generating station or 

 sub-station. If such stray or vagabond currents 

 merely traverse moist soil in widespread paths 

 they do no damage ; but if a waterpipe, or other 

 metallic object, lie along their course, some of the 

 current will find a readier path along such con- 

 ductor; and wherever the current emerges from 

 the metallic conductor into moist surroundings, 

 electrolytic action will ensue, corroding and pit- 

 ting the metal surface — sometimes with disastrous 

 effects. \'arious palliatives, such as the better 

 bonding of the return rail tracks, the use of return 

 feeders, the careful connecting of the negative side 

 of the system to the metallic pipes or other objects 

 by metal connectors, have been used, including 

 the employment of appliances called negative 

 boosters. 



The first-named of the monographs before us is 

 devoted to a discussion of the electric conductivity' 

 of various kinds of soils under various conditions 

 of moisture, pressure, and temperature, and the 

 effects of these factors on the electrolytic corrosion 

 question. Methods of measuring the resistivities 

 of soils in situ, as well as in the laboratory, are 

 discussed. The soil of cities app>ears to be more 

 highly conductive than that of country districts by 

 reason of absorption of drainage and sew-age. The 

 presence of refuse in " made " land is distinctly 

 promotive of conductivity, and therefore of elec- 

 trolytic corrosion. The authors of the monograph, 

 Messrs. McCollum and Logan, have done their 

 work thoroughly, and have added statistical tables, 

 which, in countries like the United States, where 

 legislation has not intervened to stay the damage, 

 must be very valuable. 



The second memoir, by Messrs. Rosa and 

 McCollum, is a lengthy discussion, as an engineer- 

 ing problem, of the mitigation of electrolytic cor- 

 rosion, or as they rather unfortunately describe it, 

 of "electrolysis." They deal with corrosion in 

 reinforced concrete ; with attempts to prevent 

 corrosion by protective coatings of paint ; with the 

 use of insulating joints in pipes ; with electrical 

 means of combating or compensating the tendency 

 to stray currents; with summaries of the various 

 legal regulations in use in different countries. It 

 appears that the Bureau of Standards has issued 

 eight different publications on this subject. The 

 present memoir alone extends to more than 143 

 pages. 



