164 MR. RENNIE’S EXPERIMENTS ON THE FRICTION AND 
That the friction of cast iron on cast iron was still further diminished by hogslard. 
That the friction of yellow brass on cast iron was increased by light weights and diminished by 
heavy weights, perhaps from being less fluid and sensible in the one case, and more capable of pre- 
venting the contact of metals in the other. 
That gun metal on cast iron with hogslard gave less friction than with oil. 
That yellow brass on cast iron with anti-attrition composition of black-lead and hogslard, increased 
friction with light weights, and greatly diminished it with heavy weights, showing extremely irregular 
results. 
That yellow brass on cast iron with tallow gave the least friction, and may therefore be considered 
the best substance under the circumstances tried. 
That yellow brass on cast iron with soft-soap gave the second best result, being superior to oil. 
That yellow brass on cast iron with soft-soap and black-lead gave the worst result, diminishing the 
friction in the inverse ratio of the weight. 
Conclusion. — That the diminution of friction by unguents varies as the insistent weights and natures 
of the unguents ; the lighter the weight the finer and more fluid should be the unguents, and vice 
versa. 
Table X. 
Experiments on Velocities in Friction. 
A cast iron Cylinder with two bearings of one inch wide, six inches diameter, with two side 
collars one-eighth of an inch deep ; a rope of three-eighths of an inch diameter wound round the 
cylinder. Bearing surface 12^ square inches. (Plate V.) 
i 
Without Oil. 
Weight in 
roller scale. 
Weight required 
to move the roller. 
Height 
fallen. 
Time in falling. 
Remarks. 
Proportion. 
lbs. 
oz. 
lbs. 
OZ. 
Seconds. 
348 
8 
112 
0 
Four trial experiments 
3.11 
300 
0 
112 
0 
5 
made by decreasing 
2.67 
280 
0 
114 
0 
7 * 
weight ; very unsteady 
motion. 
2.45 
280 
0 
114 
0 
7f 
* Began to grind. 
2.45 
280 
0 
228 
0 
H 
f Grinding increasing 
1.22 
224 
8 
112 
0 
6 
with stopping. 
2.00 
224 
8 
112 
0 
4± 
2 
2.00 
174 
8 
58 
0 
4 
3.00 
174 
8 
58 
0 
4 
3.00 
174 
8 
116 
0 
21 feet 
2 
1.50 
174 
8 
116 
0 
2 
1.50 
160 
8 
56 
0 
7 
2.86 
160 
8 
56 
0 
8 
2.86 
66 
8 
28 
0 
8 
2.37 
62 
8 
22 
0 
4 
2.84 
62 
8 
22 
0 
4 
2.84 
62 
8 
44 
0 
2| 
1.42 
62 
8 
44 
0 
4 
1.42 
62 
8 
44 
0 
H 
1.42 
