266 



SCIENCE. 



[N. S. Vol. XXIV. No. 609. 



The most competent opinion that could be 

 obtained was that if the differences of po- 

 tential due to stray ground traction or 

 other currents could be adjusted to be 

 within three volts or less, the difficulty 

 would cease, as the trouble was all due to 

 stray grounded currents from electric rail- 

 ways. To that end, the stray currents 

 were measured, and at times a difference 

 of potential of nine volts higher than the 

 harbor was discovered between the railroad 

 rails in the freight yard and the river, pro- 

 ducing a considerable flow of current from 

 all parts of the water piping and other 

 metallic substances in the vicinity of the 

 power house site to the harbor. 



In order to properly study the real con- 

 ditions,, a number of glass jars were pro- 

 vided and various combinations of metals 

 were immersed in samples of water taken 

 from the river, of sea water, and of pure 

 water. The action of the river water was 

 much more violent than ordinary sea water. 

 It was further observed that there was a 

 local action going on which was galvanic, 

 and that the amount of stray currents 

 caused the galvanic action to be exceeding- 

 ly violent, and that thin copper tubes were 

 destroyed at a very rapid rate. They 

 would be punctured in from four to five 

 days, which would make their use fatal in 

 commercial practise. It is thus evident 

 that there was a violent action between the 

 zinc and copper of the brass tubes which 

 were in contact with the electrolyte. Even 

 when unconnected, or electrically sepa- 

 rated, p'ates of brass were placed in this 

 electrolyte, any projections were promptly 

 destroyed. But if an electric battery hav- 

 ing a pressure exceeding that of the couple 

 in the East K.iver water was caused to act 

 to produce a counter current, and having 

 a pressure exceeding that of the galvanic 

 couple, the capacity of this electrolyte to 

 drive off atoms of the mechanically com- 

 bined metals of the alloys used was over- 



come and corrosion was arrested. To do 

 this it was planned in this case, where this 

 couple is about 0.4 of a volt, to put a 

 counter pressure of 0.6 of a volt on the 

 anode. In order to insulate the condenser 

 as much as possible from stray currents 

 from the railway, the joints in the piping 

 and the ground contacts were insulated, 

 and even the large water connections were 

 lined with glass melted on to the surface. 

 To furnish the desired electromotive force 

 a three-K.W, motor-generator was installed 

 and provided with switchboard apparatus 

 and appliances, together with ammeters 

 and voltnieters, and a connection to the 

 outlying anode in the condensing supply 

 intake at its harbor end. This led to con- 

 siderable discussion as to the methods and 

 reasons why the corrosion was prevented. 

 Reference was made to Faraday's laws, 

 and to the results of the experiments of 

 Helmholtz and Clausius. The best expla- 

 nation is given in Professor Oliver J. 

 Lodge 's ' Modern Views of Electricity. ' All 

 the apparatus was designed in accordance 

 with his theory and statements. Its opera- 

 tion has extended over a period of fourteen 

 months, and with the exception of about 

 ten tubes which have become pitted, the 

 results have been satisfactory. When the 

 condenser was planned, the condenser man- 

 ufacturer was told to slope the tubes down 

 one inch in the direction of flow ; but when 

 they performed the act, they forgot that 

 the middle inclination, if parallel to the 

 first and third passes, would then be up- 

 hill for the circulating water, and that 

 when the condenser was shut down all the 

 water would drain out of this middle sec- 

 tion except that in the bottom tubes. These 

 bottom tubes, it has been found, have be- 

 come somewhat corroded, although not seri- 

 ously. 



The cause for this result having now 

 been found, its prevention has been effect- 

 ed by perforating the diaphragm in the 



