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 roimd the 

 cylinder. Bearing surface 12^ square inches. (Plate V.) 



Without Oil. 



Height 

 fallen. 



21 feet 



Time in falling. 



Seconds. 



5 



7* 



It 



4^ 

 4 

 4 

 2 



2 

 7 

 8 

 8 

 4 

 4 



2I 



Remarks. 



Four trial experiments 

 made by decreasing 

 weight ; very unsteady 

 motion. 



• Began to grind. 



■f Grinding increasing 

 with stopping. 



Proportion. 



3.11 



2.67 

 2.45 

 2.45 

 1.22 

 2.00 

 2.00 

 3.00 

 3.00 

 1.50 

 1.50 

 2.86 

 2.86 

 2.37 

 2.84 

 2.84 

 1.42 

 1.42 

 1.42 



-^i. 



