28 Messrs. Hutchinson and Wilkes's Comparison of 



Giving the tubes equal weights in the final average, we 

 have : — 



Tube II ^=-95319 



„ IV r= -95343 



„ V r = -95349 



„ VI r = -95320 



Mean . . . -95333 

 Arranging the tubes in the order of ratio of length to 

 diameter, we have 



Table IV. 



Tube. 



Diameter. 



Ratio of length 

 to diameter. 



r. 



I. 



tnillim. 

 1763 



724 



•95255 



VI. 



1-352 



1120 



•95317 



II. 



•985 



1320 



•95320 



V. 



•670 



2650 



•95349 



IV. 



•334 



2730 



•95343 



This table shows the effect of the sinking-in of the fingers, 

 in taking the tubes full of mercury, for if we take tubes IV. 

 and V., in which this ratio is roughly the same, the variations 

 in r may be due to other causes. So too, tubes II. and VI., 

 in which this ratio is roughly the same, agree. 



Observations were taken, as suggested above, to determine 

 the correction for tube VI. The quantity obtained is a 

 difference and, therefore, difficult to determine accurately. 

 The results are given below : — 



Table V. — Correction necessary in case of Tube VI., to 

 reduce for sinking-in of fingers in taking full tube. 



Number of observation. 



Correction in 

 T oV o of 1 per cent. 



1 



2 

 3 

 4 



Average 



+ 44 

 + 23 

 + 15 



+ 28 



= + 27-5 = + -00026 



