140 KEPOET— 1893. 



in 1000. Mr. Crompton's resistance is a rectangular sheet of manganine, 

 and the potential terminals are two screws inserted at a suitable distance 

 apart in the median line. The screws are not soldered. I thought it 

 would be of interest to unscrew them, screw them up again, and re- 

 measure the resistance. The results were — 



August 10, morning -00050328 



,, 10. afternoon -00050322 



„ 10, „ -00050327 



Mean . . -00050326 



indicating a variation of about one part in 500. I unscrewed them again, 

 and after screwing them made a new measurement with the following 



results 



August 11, morning -00050398 



„ 12, „ -00050403 



Mean . -00050401 



which, compared with the first value "00050222, shows a variation of, 

 approximately, one part in 280. 



We may therefore conclude that if an accuracy of yV^'^ P^^' cent, is 

 required of a standard so constructed its potential terminals ought not 

 to be meddled with after its resistance has been determined. 



In making these measurements my direct object has been to obtain an 

 accurate and ready method of measuring standards of low resistance. 

 But I think something more than this comes out of them. It would be 

 possible in the light of our present experience to constract a Lorenz 

 apparatus considerably more accurate and easier to use than that in my 

 laboratory at Cardiff. Such an apparatus placed, let us snppose, in the 

 National Laboratory, of which we have heard a good deal at recent 

 meetings of the British Association, might with advantage be kept in 

 constant use, not only for the calibration of low resistances, but also as 

 embodying in concrete form a proper ultimate standard of electrical 

 res-istance. We have not in our electrical standard legislation given full 

 credit to the mechanical engineer for what he can do for us ; and I think 

 that a coefficient of mutual induction arranged, as in the Lorenz method, 

 80 as to be easily combined with a time would afford a more satisfiactory 

 standard of resistance than any wire coil or coils, and one easier to use 

 for purposes of ultimate reference than any mercury column. 



The Application of Photography to the Elucidation of Meteoro- 

 logical Phenomena. — Third Report of the Committee, consist- 

 ing of Mr. Gr. J. Symons {Chairman), Professor E. Meldola, 

 Mr. J. HoPKiNSON, and Mr. A. W. Clatden {Secretary). [Drawn 

 up by the Secretary.) 



Your Committee beg to report that their work has progressed slowly 

 during the last year, though it has been greatly hindered by the appoint- 

 ment of their secretary as principal of the new Technical and University 

 Extension College at Exeter. The large amount of work involved in the 



