162 



Mr. R. Sabine on a New Determination of 



tubes used in the original determination remained unbroken. 

 These, with two new ones (numbered 7 and 8), were exactly- 

 measured, and the weights of their contents of mercury, reduced 

 to 0° C, found to agree with the former reduced weights to within 

 0*05 per cent. The resistances of the tubes were compared this 

 time with spirals of glass tube, also filled with mercury. Their 

 agreement was also within the limits which may be ascribed to 

 errors of observation and of the measuring-apparatus. 



The unit of this reproduction has found employment by many 

 physicists, and very extensively in telegraph measurements, both 

 in England and on the continent. 



For the present and second reproduction, ten tubes were 

 used — four of those of the previous determinations remaining 

 unbroken, and six new ones. 



The new tubes were selected after a rough calibrating, and 

 ground off in lengths of a metre or less. They were then cleaned 

 with concentrated sulphuric acid, rinsed with distilled water, 

 dried by pumping dry air through them, and finally wiped by- 

 drawing through them a little lump of cotton wool attached to 

 the end of a couple of spirally-twisted silk-covered wires. 



The tubes were finally calibrated as follows : a drop of mercury 

 was sucked into one end, its length not exceeding 40 millims. 

 The tube was then layed upon a metre scale and the lengths (L) 

 of the mercury thread measured, with aid of a small finely-divided 

 scale and telescope, from one end to the other, at intervals of 20 

 millims. 



The readings are collected in the following Table : — 



Table I. 



Place. 

 10 



3. 



5. 



7. 



8. 



10. 



11. 



12. 



13. 



14. 



1 15. 



141 



200 



7-8 





150 



14-4 



120 



11-2 



170 



161 



30 



141 



199 



7-8 



34-8 



14 95 



14-45 



11-9 



11-3 



17-0 



161 



50 



141 



201 



7-85 



34-9 



149 



1445 



120 



11-4 



170 



161 



70 



141 



20-2 



79 



35-0 



14-8 



145 



12-0 



11-5 



171 



161 



90 



141 



20-2 



7-9 



351 



14-7 



14-6 



120 



11-4 



171 



16-1 



110 



14-2 



202 



7-85 



35-3 



14-6 



146 



120 



11-3 



171 



161 



130 



14-4 



201 



7-8 



35-6 



14-5 



14-6 



120 



11-3 



171 



161 



150 



14-5 



20-2 



7-7 



360 



14-5 



14-6 



119 



11-35 



171 



161 



170 



14-5 



203 



7-7 



360 



14-4 



11-6 



119 



11*4 



171 



1605 



190 



146 



203 



7-8 



35-9 



143 



146 



11-8 



11-4 



171 



160 



210 



14 7 



20 2 



78 



35-75 



14-2 



14-6 



11-75 



11-4 



1715 



160 



230 



150 



20-3 



7-7 



35-7 



141 



14-6 



11-65 



11*4 



17'2 



160 



250 



150 



206 



765 



356 



141 



14-6 



115 



11*4 



17-2 



160 



270 



150 



20-7 



7-7 



35-7 



14-2 



14-6 



11-6 



11-3 



17-1 



160 



290 



15-2 



20-7 



775 



35-8 



142 



14-6 



11-7 



11*3 



171 



16 



310 



15-4 



207 



775 



360 



140 



14-6 



11-7 



11-3 



171 



15-9 



330 



15 5 



20 7 



7-8 



360 



139 



14-6 



11-8 



11-25 



1705 



15-8 



350 



15-5 



20-7 



7-8 



36 1 



13-8 



14-6 



118 



112 



170 



15-7 



370 



15-5 



207 



7-8 



36-0 



138 



14-6 



11-9 



11*2 



170 



15-7 



