34 REPORTS ON TBE STATE OP SCIENCE. 



the Laboratory. The behaviour of the various coils is somewhat different ; 

 while some have been very constant, others appear to have changed con- 

 siderably. 



At the Conference on Electrical Units, held at the Reichsanstalt in 

 1905, it was suggested that the Jena glass 59"' was, from its good elastic 

 properties, the best glass to employ for mercury resistances, and accord- 

 ingly efforts have been made to get some suitable tubes. Five tubes of 

 16'" have recently been secured, after great difficulty, which will probably 

 do for standards. Tubes of 59'" have not yet been obtained : the 

 difficulty of drawing them is a serious obstacle to their use. 



A number of tubes of French glass, ' verre dur,' are also on order. 



Progress has also been made during the year in the design of the 

 Lorenz apparatus, to be given by the Drapers' Company, and the manu- 

 facture of the bed and the heavy-metal work has been entrusted to Messrs. 

 Armstrong, Whitworth &, Co., who have kindly undertaken it. The 

 marble cylinders required have been delivered at the National Physical 

 Laboratory. 



Preparations for the holding of an International Congress on Electrical 

 Units in London in October next are well advanced. 



Specifications dealing with the international ohm, the international 

 ampere, and the Weston cadmium cell, which have been prepared at the 

 National Physical Laboratory after consultation with other workers to 

 serve as a basis of discussion at the Congress, are given in the Appendix 

 with a view of making them known. 



The grant of 50^. made to the Committee at Leicester has been spent 

 in great part in the purchase of materials for the Weston cells and the 

 silver voltameter research and in obtaining suitable tubes for use for 

 standards of resistance. 



The balance now in hand is 11. Os. 4c?., and the Committee recommend 

 that they be allowed to retain this for the purpose of continuing the 

 experiments now in progress. 



The Committee therefore recommend that their Reports from 1862 

 onwards be reprinted, after careful editing, as a memorial to Lord Kelvin, 

 and that they be reappointed, with a grant of 100/. in addition to the above 

 unexpended balance, for the purpose of undertaking this work and con- 

 tinuing their researches on the standards ; that Lord Rayleigh be Chairman 

 and Dr. R. T. Glazebrook Secretary. 



APPENDIX I. 



On the Secular Changes of the Standards of Resistance at the National 

 Physical Laboratory. By F. E. Smith, A.R.C.Sc. 



(b'rom the National Physical Laboratory.) 



It has long been known that many resistance coils of platinum -silver, 

 of manganin, and of other resistance alloys do not keep constant in 

 resistance. The causes of the changes may lie in some alteration in 

 structure of the alloy, of some change in strain, of surface action, of 

 faulty joints, or, as suggested by Dr. Rosa, they may lie in the insulating 

 medium. 



