CHEMICAL APPARATUS. 



99 



on which they slide up and down; there is an iron ball, 

 about three inches in diameter, having a ring in it for more 

 convenient handling, and having a stand supporting it 

 opposite the centre of the mirrors, and also a differentia? 

 thermometer, supported by a mahogany stand. 



To use, place the mirrors at the same height, on a table, 

 exactly facing each other, and from ten to fifteen feet apart 

 And in the focus of one of the mirrors (usually four and a 

 half to five inches) place the iron ball, heated a little below 

 redness, and in the focus of the other mirror, place the 

 thermometer, which will indicate a considerable elevation of 

 temperature. Place a piece of phosphorus in the focus of 

 the mirror, and it will be ignited. 



The rays of heat from the iron fall on the nearest mirroi 

 and are reflected in a direction parallel to the axis of the 

 mirrors ; they then meet the second mirror, and are con- 

 centrated on the thermometer, or phosphorus, in the focus 

 of the mirror. Care must be taken to have the mirrors 

 arranged in a common axis. 



Price, of 12-inch planished tin, with iron ball 



stands and differential thermometer, $ 8.00. 

 " of 12-inch brass, - $20.00. 



" of 18-inch, " - - $32.00. 



Leslie's experiment of a vessel on a stand having different 



Price, $1.50. 



radiating surfaces. 



Fig. 563 



The Still (Fig. 

 563.) An appara- 

 tus for the distilla- 

 tion of liquids. It 

 includes the body, 

 or boiler, to which is 

 attached the head, 

 forming the com- 

 munication between 

 the boiler and con- 1 

 denser, or worm- 

 pipe, from the ex- 

 tremity of which the distilled liquid passes in successive 

 drops, or a small continuous stream. As these stills are 

 made to act by means of a lamp, the whole process of dis- 

 tillation may be performed on the table, without dirt, offen- 



