Brown. — Action of Fusible Cutouts. 



359 



two can be compared is by the values of the fusing- 

 currents themselves. Here there is some slight difficulty, 

 owing to an alteration of the values assigned to the fusing- 

 currents in the ratio of 1,800-6 to 1,642 between the years 

 1887 and 1888. This is referred to as a verification of the 

 " dimensions of the currents as detailed in my paper read on 

 the 22nd December, 1887," but whether it is a recalibration 

 of standards, the result of further tests, or a recalculation of 

 means does not appear. I have taken it that the means have 

 been recalculated. 



My tests (column 4) are of tin wires, very long, horizontal, 

 in free air, and tested with alternating current of 80 periods. 



The agreement of Sir W. Preece's experimental results 

 with his law is remarkably good, except, as he pointed out at 

 the time, for the fine wires, which are of not much import- 

 ance. But my results, while agreeing well with those of Sir 

 W. Preece from 14 to 20 mils, show a decided divergence 

 at the largest observed value, and a very serious divergence 

 from the calculated figure for the largest wire which I tried. 



The difference between my value and Sir W. Preece's for 

 the largest wire he tested is about 32 per cent. With regard 

 to this I have first to remark that I have found, for the parti- 

 cular dimensions referred to, a cooling effect from the termi- 

 nals of about 4 per cent., which, applied to Sir W. Preece's 



* Apparently not observed. 



