proceedings: philosophical society 371 



The 805th meeting of the Society' was held at the Cosmos Club, April 

 13, 1918; President Burgess in the chair; 49 persons present. The min- 

 utes of the 804th meeting were read in abstract and approved. 



The first paper was presented by S. J. Mauchly, on A study of pres- 

 sure and temperature effects in earth-current measurements. (Illustrated 

 by lantern sUdes). The larger portion of the earth-current data on 

 record, was obtained from observations made on commercial telegraph 

 lines. For lines of considerable length, the fluctuations in the observed 

 current are generally assumed to be very little influenced by local ef- 

 fects at the earth plates, but for measurertients made between electrodes 

 not many kilometers apart, this assumption is not valid. Most of the 

 special lilies installed for the study of earth-current phenomena are 

 necessarily limited in extent, and the object of the experiments de- 

 scribed in this paper was to investigate the nature and order of magni- 

 tude of some of the spurious effects which may function under these 

 conditions. 



In one group of experiments a method similar to that used by Des 

 Coudres, in his study of the E.M.F. produced by the action of gravity 

 in salt solutions, was used to investigate the possible presence of an ef- 

 fect due to difference of pressure at the electrodes. It was found that a 

 tube filled with soil and provided with an electrode at either end showed 

 a component of the total E.M.F. which tended, when the tube was ver- 

 tical, to form a cathode at the lower electrode regardless of which elec- 

 trode was involved. The order of magnitude of this effect was shown 

 to be sufficient to account for certain observed phenomena which ap- 

 pear inconsistent with physical principles, provided the effect exists as 

 a general phenomenon in nature. 



The results of continuous measurements of P.D. and temperature 

 difference made on actual underground systems of earth plates for 

 about eight months show that most, if not all, of the diurnal variation 

 which has by some observers been ascribed to a vertical earth current 

 was very probably due to the variations in the temperature difference 

 between the electrodes. 



The spurious effects introduced by temperature-difference variations 

 were found to be greatly increased and reversed in sign when the soil 

 in contact with the electrodes was frozen. 



While the results are strictly applicable only to the actual installation 

 employed during the experiments, they show that the effects which may 

 result from temperature difference at the electrodes of an earth-current 

 line, and from the variations in this difference, may for short lines be of 

 the same order of magnitude as the quantities to be measured and with 

 which they are associated. Some of the phenomena which various 

 observers have ascribed to a true earth current must be largely influ- 

 enced by such effects. The employment of nonpolarizable electrodes 

 does not prevent the introduction of temperature-difference effects. 



The paper was discussed by Mr. Bauer. 



Mr. M. Sasuly then presented the second paper, on A general system 

 of approximate integration formulae. Several types of quadrature for- 



