430 Mr. E. H. Hall on the Rotation of the 
Rolled.’’ This steel, as it came from the dealers, was pliable 
and soft enough to be quite readily cut with a pocket-knife. 
The first strip to be described was tested in this “ natural ” 
condition. 
No. 1 (untempered). 
Length of main strip when weighed . 4:13 cm. 
Width of main strip when weighed. . 1:10cm. 
Area of whole strip when weighed . . 4°88 sq. em. 
Weight ah ene Par 4-21 grm. 
Deéinsityio\ C's 2. Spee aon Se: hs ea age 
Average thickness from these data. . 01092 cm. 
Hstimated thickness between arms . . ‘01116 cm. 
Distance from B to B, about. . . . 31em. 
No. 2 (tempered). 
The dimensions of this strip were not so accurately taken. 
It was so brittle that I felt obliged to use caution in applying 
the calipers to it. It appeared to be of about the same thick- 
ness as No. 7, and I assumed it to have exactly the same thick- 
ness. The distance from B to B was about 2°6 cm. 
Results obtained with these two strips are shown in the 
following table :— 
Date. Temp. M. C. tite Se 
No. 1. Nov. 24. | 187 | 1647 | -0970 | +12000%10-18 
i y 25 | 1629 | 1007) | 4oiesonei 
16:2 770 
No. 2. Dee. 1. 180 | 1602 | -0s70 | +32790x ,, 
‘i 3 1:9 | 1587 | 0908 | +80800x. ,, 
16-1 1920 
Decrease for 1° fall of temperature, approximately °4 per cent. 
The magnitude of the rotaticnal coefficient in the soft steel 
is about 14 times, and that in tempered steel about 4 times as 
great as that in the soft iron. This agrees very well with the 
conclusion drawn from the hasty experiments of the year before, 
when a piece of steel from a clock-spring was used. When a 
sensitive galvanometer is used, an ordinary permanent horse- 
shoe magnet of half-inch bar produces an easily discernible 
effect in the strip of tempered steel. 
It should be stated that two or three months before the 
