BETWEEN SUEEACES MOVING AT LOW SPEEDS. 
521 
V. Steel on Brass. Oiled. 
1. Friction uniform from velocity (M)002 foot per second 
to greatest velocity observed, 00044 foot per second . ^=0*146 
2. Friction uniform from velocity 0-0002 foot per second 
to greatest velocity observed, 0-0064 foot per second . ^=0T46 
Mean ^=0*146 
Here the coefficient appears to be entirely unaffected by change of velocity. 
VI. Steel on Brass. Wet with water. 
1. Friction uniform from velocity 0-0002 foot per second 
to greatest velocity observed, (>0048 foot per second . ^=0*106 
2. Friction uniform from velocity 0-0002 foot per second 
to greatest velocity observed, 0-0045 foot per second . ^o = 0*102 
3. Friction uniform from velocity 0’0002 foot per second 
to greatest velocity observed, 0-0041 foot per second . ^=0‘107 
Mean ^=0-105 
The coefficient here is remarkably low, indicating, when compared with the pre- 
ceding, that, at least when the intensity of pressure is very great, water is a better 
unguent than oil for surfaces of steel and brass. 
VII. Steel on Polished Agate. Bry. 
1. Friction not very regular, but apparently independent of 
velocity. From velocity 0-0002 foot per second to 
greatest velocity observed, 0-0064 foot per second . . ^=0T68 
2. Ditto. From velocity 0-0002 foot per second to greatest 
velocity observed, 0 0053 foot per second ^=0*191 
3. Friction uniform from velocity 0-0002 foot per second 
to greatest velocity observed, 0-0065 foot per second . ^=0-240 
Mean ^=0*200 
The remarks made in Case I. apply here. 
