420 Mr. C. A. Bell on the Determination 



3. From Messrs. Baird & Tatlock. 



Mean product for nine rods at 9° = 525990. Lengths about 



3 cms. ^ = 2-488. 









nX'21 observed. 







a (corrected). 



524310 







527360 



530640 







527180 



527900 







526710 



527480 







526900 



517660 







526370 



Mean 



a at 6°: 



= 527040 cm. per sec, 







at 0° 



= 527170. 



E'= 



•6-91 



x 10 11 at 0°. 



The last result here has been rejected. For this very 

 irregular rod AZ was +2*36 cms. 



i 



Bohemian Glass. 



From Messrs. Baird & Tatlock. This glass was obtainable 

 only in thin tubes, very irregular, much streaked and full of 

 knots. 



Mean product for six tubes = 513740 at 6°. Lengths about 

 138 cms. Po = 2*394. 



n X 21 observed. 



a (corrected). 



524580 



518780 



511690 



515430 



511740 



516950 



511040 



517260 



512050 



516220 



511360 



515800 



Mean a at 6°= 516740 cm. per sec. 

 at 0° = 516880. 

 E'=6-39xlO n atO°, 

 or, rejecting the first result, 6*38 x 10 11 . 



The agreement here is not nearly so good as usual, as 

 indeed was anticipated. 



Gauge- tube Glass. 



A hard, ferruginous, light-green glass, almost infusible, 

 manufactured by Messrs. Powell & Sons of Whitefriars, 

 specially for gauge-tubes. Four carefully-chosen tubes, about 

 112 cms. in length, were examined. The external diameter 



