LANE ON MAGNETIC. PHENOMENA. 167 



that they know this to be the rule. Tliis ii)aj2;netic force is soinetimes 

 very considerable. It will often liohl out the larj^est size of spike, and 

 I believe in the case of the well over tive thousand feet deep, tested by 

 Prof. William ITallock of Columbia Tnivi'sity. it could liold a wrench. I 

 have found that in lowering; a thermometer down these wells tlie steel tape 

 clung to the sides so that it made a material ditlerence in the energy re- 

 quired to handle it. It was just about as much as a man could do to 

 start 2,(>0() feet of steel tape from the Grayling well, although the weight 

 of the tape itself would not be over 25 ])ounds. Again in measuring the 

 depth of a well recently sunk at Cheboygan, 2,700 feet deep or more, Mr. 

 Rust the driller, informed me that the magnetic drag on the tape was 

 such that it was also impossible to tell when the 20 pound weight was at 

 the bottom. At the same time it seems to me that the magnetism is not 

 directly proportional to the depth of the hole alone, although the larger 

 and deeper holes are of course in a general way more magnetic, and I 

 should think there might be interesting op])ortunity for some student of 

 geophysics to make some magnetic observations of considerable interest. 

 The university of Michigan has for instance put down recently a well 

 dome 1,300 feet deej), which at one time, if not at present, was cased over 

 a thousand feet. It would seem that here might be a good chance for 

 careful experiment. I should be very glad to have any suggestions from 

 students of physics as to how observations upon these phenomena could 

 be made more definite and instructive. Before closing I would like to 

 mention another phenomenon though it does not occur in a deep boring 

 but in a deep shaft. The Tamarack mine has recently sunk a shaft (No. 

 5), which goes vertically downward some 4,600 feet before it encounters 

 the lode which the mine is working. In preparing to connect this with the 

 old workings of the mine two plumb bobs or pendulums were let down the 

 shaft 4,250 feet, and whereas they were 17.58, or at another time 16.3o, 

 feet apart at the top, they were found to be 17.65 respectively 10.42 feet 

 apart at the bottom. In No. 2 shaft the divergence was from 12.0 feet at 

 the top to 12.7 feet at the bottom. This divergence was unexpected, but 

 Prof. W. Hallock of Columbia who has investigated the matter, concludes 

 that it is a phenomenon of a character similar to those we have described 

 that the long wires in the magnetic field of the earth were magnetized, so> 

 that the similar poles repelled each other as they always do. He adds, 

 *'I may say that, as far as the magnetizing inttuence of the earth upon 

 the casings is concerned, it would matter but little whether the pipes were 

 really wrought iron or steel, because, inasmuch as they remain in the 

 magnetic field, they would of course remain magnetized, even if they 

 were soft wrought iron. 



''A factor which probably iuHuenccs the strength of the magnetism of 

 these casings is the number of strings that may be put into any i)articular 

 well. In the well at Wheeling there were, I believe four strings, the 

 longest one being something over 1.500 feet. In that well it proved im- 

 possible to sink a steel tape through the casing, even with a 50 pound 

 weight attached to the lower end of it. In my temj>erature observations 

 a steel wire was used which of course adhered to the walls of the well but 

 little." 



Farther investigation at the Tamarack Mine l»y President McXair 

 showed that the ]»henomenon there was mainly due l<» the draft of air. 



