44 



REPORT — 1903. 



The Wolff manganin coils of the Association are also given at 16° C, 

 with a temperature coefficient to be applied for small ranges of tempera- 

 tui'e only, since it is by no means a linear function. 



Table XIV. 



As has already been explained, the values are given in terms of the 

 Laboratory unit which represents 10'^ C.G.S. units of resistance as deter- 

 mined by Lord Rayleigh and Mr. Glazebrook at Cambridge ; it has been 

 assumed that the inter-comparison of ths coils enables that unit to be 

 recovered. 



Appendices I. and II. of the present Report afford the means of con- 

 necting this unit with those of the Board of Trade, derived from it in 

 1891, and of the Reichsanstalt, and also with the ohm or international 

 ohm— the resistance, that is, of a certain column of mercury. 



APPENDIX IL 



The relation between the international ohm (106"300 cm. Hg. weighing 

 14"4.521 gms. at 0° C) and the unit of resistance einjjloyed at the N.P.L. 

 Preliminary Note, by F. E. Smith. 



(From the National Physical Lahoratory.') 



The following measurements of six mercury tubes indicate the progress 

 made in this inquiry, and also the relation obtained :— 



Thus, Laboratory Unit of Resistance = -99991 Int. obm. 

 _ 106 291 

 ~ 106-300 

 [The above figures are intended as merely provisional.] 



Int. ohm. 



' No. 381 ig a mapganin coil bglongipg to the Board of Trade, 



