BETWEEN SUEFACES MOVING AT LOW SPEEDS. 
525 
XIV. Steel on Beech. Oiled. 
The results obtained in the corresponding experiment with greenheart appear again 
here. 
1. For velocity 0*0002 foot per second ^=0*126 
For velocity 0*005 foot per second ^ = 0*100 
Greatest velocity observed 0*0057 foot per second. 
2. For velocity 0*0002 foot per second ^=0*126 
For velocity 0*005 foot per second ^=0*101 
Greatest velocity observed 0*0055 foot per second. 
3. For velocity 0*0002 foot per second ^=0*126 
For velocity 0*0037 foot per second ^=0*110 
Greatest velocity observed 0*0037 foot per second. 
In the last experiment it appears that the higher limit of the velocity was not high 
enough to enable p to assume its minimum value. We therefore reject it in estimating 
the means, which are as follows : — 
Mean value of p for velocity 0 0002 foot per second .... 0*126 
Mean value of p for higher limit of velocity 0*101 
The change in the value of ^ occurs here below a velocity of 0*005 foot per second. 
The total change is almost exactly twenty per cent, of the higher value. 
XV. Steel on Beech. Wet with water. 
Here again we have an equally unmistakable increase of the coefficient of friction as 
the speed diminishes. 
1. For velocity 0*0002 foot per second ^ = 0*344 
For velocity 0*007 foot per second /^=0*254 
Greatest velocity observed 0*007 foot per second. 
2. For velocity 0*0002 foot per second ^=0*353 
For velocity 0*008 foot per second (jj= 0*290 
Greatest velocity observed 0*008 foot per second. 
3. For velocity 0*0002 foot per second ....... ^=0*370 
For velocity 0*0074 foot per second 0*292 
Greatest velocity observed 0*0074 foot per second. 
The curves for these observations connecting [m with the velocity indicate pretty clearly 
that the greatest velocity observed was insufficient to brings to its least value. Taking, 
however, the means of the observations as they stand, we have 
Mean value of for velocity 0*0002 foot per second . . . . 0*356 
Mean value of p for highest velocity observed 0*279 
A comparison of all the above results shows that, omitting the doubtful cases of oiled 
MDCCCLXXVII. 4 E 
