8 



Transactions of the Society. 



2nd band (Woo in."). 



the last nine bands will show the extent of that factor in the 

 original measures. 



"This idea has been carried out, with the following results, 

 which indicate the high accuracy of Mr. Grayson's rulings. The 

 mean of the first band re-measured equals 762-9 divisions. 



Drum Divisions 



Mean of five TT ,Vo in. readings 763* 1 



762-4 

 764-1 

 758-8 

 760-6 

 758-4 

 758-6 

 758-9 

 758-6 



It will be noted that screw errors are thus revealed and 

 differentiated. Another remarkable circumstance is the startling 

 agreement of the last four means, an exactness which perhaps 

 suggests some little coincidence, especially as the fractional 

 division readings, from which the means are obtained, are neces- 

 sarily only estimated tenth parts. Be this as it may, it is obvious 

 that the probable error is exceedingly small. 



