9B Mr. G. Gore on the Rotation of 



on the outer surface of the metal. "When the balls are exceed- 

 inghj thiu, slight indentations occur upon the outer surface, as 

 if that surface was relieved from a state of mechanical tension. 



In using the apparatus, the triangular support is placed in a 

 firm and steady position upon a board containing three shallow 

 holes to receive the feet ; the ring is placed upon the triangle 

 and set to a perfect level, either by means of a spirit-level ov 

 bne of the balls. The ring is then placed in a red-hot closed 

 muffle and heated to bright redness (the hotter the better, so 

 that it is not fused) ; it is then taken out and placed carefully 

 upon its support by the aid of the guide-pins G G, and the ball 

 at once placed steadily upon it. As soon as the ball commences 

 to revolve the time is noted, and the number of revolutions also 

 noted during 30 seconds, and, if desired, during half a minute 

 longer. If other experiments are to be tried, the ring is at 

 once replaced in the muffle. In the various experiments I have 

 made, the ring has occupied 8 minutes in first acquiring its 

 heat, and 5 minutes each time of renewing it. 



The following is a list and description of the balls which have 

 been experimented with ; they were all formed of the best qua- 

 lity of German silver (except A, which was composed of One 

 hemisphere of German silver and one of iron, and gilded). 



List of Balls. 



A. 2| inches diameter; 756 grains weight. 



B. 3 „ }) ) 703 „ „ 



C. 3 „ }, ; 606| „ „ with a bar of Ger- 



man silver weighing 228^ grains fixed in it from pole to 

 pole*; total weight 835 grains. 



D. 3| inches diameter; 1000 grains weight, and of defective 



shape. 



E. D reduced to 774 grains weight. 



F. E reduced to 687| „ „ and a bar of German silver 



weighing 263 grains fixed axially within it ; total weight 

 950g grains. 



G. 3| inches diameter; 1029 grains weight. 



H. 3i „ „ ; 776 „ „ with a bar of Ger- 



man silver weighing 224 grains fixed from pole to pole ^ 

 total weight 1000 grains. 



I. 3| inches diameter ; 1026 grains weight, with an axial bar 

 of German silver weighing 392 grains; total weight 

 1418 grains. 



* Tlie object of using axial bars was to ascertain whether a certain 

 degree of pressure upon the rails was favourable to the success of the 

 experiment. 



