I Dip roved Design for Friction Cones. 387 



used in preference to water. These comprise in brief the 

 essential points of the improved design. If we look into 

 the action of these improved cones we shall see that, as an 

 effect of the rotation of the outer cone, the oil in the cup is 



Fiff. 1. 



forced up through the grooves Gr on to the channel S and 

 through the holes h back into the inner chamber aoain. 

 Thus the liquid is stirred efficiently and automatically and a 

 liquid of high conductivity brought into intimate contact 

 with the surface where the heat is generated by friction, 

 thus ensuring a uniform rise of temperature of the whole 

 system in the minimum of time. The liquid also gives a 

 steady and uniform lubrication for the friction surfaces, and 

 in a class-room the experiment can be done bv an average 

 student solely by himself, without any extra aid to stir the 

 liquid or to observe and take down the readings of the 

 thermometer. This modification has also the great advantage 

 that it can be directly introduced on all the existing type 

 of millions of the apparatus already in use. 



The Cavendish Laboratory, 

 Cambridge. 



