94 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



Fig. 553. 



The Ring and Ball to show Expansion by Heat. (Fig. 554, 

 as below.) This is a very elegant way of showing the samo 

 experiment as the last. It consists of a brass ball, suspend- 

 ed from a brass pillar bent over at the top ; on the pillar 

 slides an arm bearing a brass ring, exactly fitting the ball, 

 and which when cold will readily pass through ; on heating 

 the ball, by a small spirit lamp, it will be too large to pass 

 through ; when cooled it will pass as before. The whole is 

 mounted on a neat mahogany base. Price,$2.25. 



Fig. 554. Fig. 555. 



Pyrometer. (Fig. 555, as above.) This arrangement 

 consists of a base of mahogany about twelve inches long, to 

 which are attached two upright pieces which areimmovably 

 held in their position by metallic braces, extending from the 

 one to the other ; between these there is a rod of metal, 

 supported at one end from the point of a screw, and at the 

 other from the shorter end of a bent lever, the axis of 

 which is fastened to the wood. The longer end of the levei 



