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MESSES. ELEEMING JENKIN AND J. A. EWING ON EEICTION 
3. For velocity 0-0002 foot per second //,=0T19 
For velocity 0-0043 foot per second ^=0T30 
Here 0-0043 is the greatest velocity observed. 
4. For velocity 0-0002 foot per second ^=0T16 
For velocity 0-0040 foot per second ^=0*127 
From this to the greatest velocity observed, 0-0059 foot per second, ^ remains sensibly 
constant. 
Mean value of at velocity 0-0002 foot per second . . 0-118 
„ „ „ about 0"0050 foot per second . . 0-129 
It is to be observed in connexion with these values, and, indeed, in connexion with 
our experiments with unguents generally, that, owing to the very great intensity of 
pressure on the small bearing-surfaces of the axle, the unguent must have been to a 
great extent forced out, so as to leave the surfaces in the state described by Morin 
as “unctuous.” 
III. Steel on Steel. Wet with water. 
1. Friction uniform from velocity 0-0002 foot per second to 
greatest velocity observed, 0 - 0058 foot per second . . ^=0-178 
2. Friction uniform from velocity 0-0002 foot per second to 
greatest velocity observed, 0-0052 foot per second . . ^=0-205 
3. Friction uniform from velocity 0-0002 foot per second to 
greatest velocity observed, 0-0054 foot per second . . ^=0-241 
Mean p,=0-208 
The remarks made in Case I. apply here. On comparing these values with those for 
dry steel on steel, we see that the presence of water here diminishes the friction. 
IV. Steel on Brass. Dry. 
1. Friction very irregular, but apparently unaffected by 
velocity. From velocity 0-0002 foot per second to 
greatest velocity observed, 0-0059 foot per second . . 0-180 
2. Very irregular. From velocity 0-0002 to 0-0053 . . . ^=0-202 
3. Irregular. From velocity 0*0002 to 0-0056 ^=0*202 
Mean ^=0T95 
Although the friction was very irregular here, it seemed to be quite independent of 
the velocity. The coefficient is strikingly less than in the case of dry steel surfaces. 
