4 RECORDS 



SECTION OF ASTRONOMY, PHYSICS AND 



CHEMISTRY. 



January 6, 1902. 



Section met at 8:20 P. M., Professor Hallock presiding. The 

 minutes of the last meeting of Section were read and approved. 



The following program was then offered : 



William Hallock, The Magnetic Disturbance of Steel 

 Wire Plumb-bobs. 



William Hallock, A Thermograph for Soil Temperature. 



H. C. Parker, The Variation of Contact Resistance 

 WITH Change of Electromotive Force. 



Summary of Papers. 



Professor Hallock stated that in the course of the work in the 

 very deep shaft of the Tamarack Mining Co. on Lake Superior it 

 had been found desirable to plumb down certain points from the 

 surface. The plumb-lines used were of No. 24 piano wire and 

 the weights were fifty pounds of iron. At first the lines were 

 16.33 feet apart at the top and they were later moved to 1 7.66 feet 

 The remarkable observation was made that in the first case they 

 were 0.08 feet and in the second case 0.07 feet farther apart at the 

 base than at the top. It was pointed out that a deflection of 

 such an amount could not be explained as due to the gravita- 

 tional attraction of the walls of the shaft for the nearer plumb- 

 bob. Professor Hallock suggested that the effect was probably 

 due to the magnetization of the wire and the consequent repul- 

 sion of the north poles at the bottom. In order to test the 

 possible applicability of this theory a number of experiments 

 were made in the research shaft at Columbia University which 

 gave much corroborative evidence. Two plumb lines, about 

 85 feet long, were suspended in the shaft. One was of copper 

 wire and the other of iron wire about 0.03 inch in diameter. 

 Lead weights were attached and it was found that the lines 

 were about -J^ in. closer together, at the bottom, when the 

 iron line was south of the copper than when it was north. Two 

 lines of iron wire were also used and the distance apart at top 



