for Muiniaining' an Uniform Temperature. 363 



lower than the former, in order that a globular retort may approximate 

 equally to each wick. 



C. Is the platina wire about the hundredth part of an inch in diameter, coiled 



into the form of a cup, the upper part of which is one-third of an inch in 

 diameter ; this cup is supported by a pin, formed by a continuation of the 

 wire. A large headed'common pin is pricked into the centre of the wick, 

 to make an opening for the insertion of the pin of the wire-cup. The 

 head of the large pin is then placed in the bottom of the cup to depress 

 it, nearly in contact, but not to touch the wick. When all the coils of 

 wire have been thus arranged, a piece of well compressed spongy platina 

 is to be cut into small blocks, of sufficient size, to rest in each wire cup. 



D. Is a tin rim soldered to the top of the reservoir, perforated with twelve 



holes, each three quarters of an inch in diameter, for the admission of 

 air. 



E. A tin tube for supplying the reservoir with spirit. 



F. Is a glass cover with a wide neck, (this glass is precisely similar to the 



common deflagrating jars,) it rests upon a tin ledge, soldered inside round 

 the rim D, above the air-holes. 



G. Is a tin tube or chimney, which rests upon the shoulders of the glass 



cover F. 

 H. Is a screen made of tin, which is large enough to surround the glass 

 cover, and to leave a space an inch distant all round it. This screen 

 is supported by a projecting rim of tin at the bottom, on the same ledge 

 that the glass cover F rests upon. It is advisable to have the interior 

 surface of this screen lined with some material that is a bad conductor of 

 heat. 

 I. Is a glass flask or retort, rounded at the bottom, which is placed upon a 

 brass ring, supported by three legs. It is necessary to have all retorts 

 that are' used, perfectly rounded at the lower part, in order that, when the 

 apparatus is adjusted, the retort will be at an equal distance, not to 

 touch, but to be nearly in contact with each of the platina balls. 

 Belonging to the furnace is a tin cover, which is used when the apparatus 

 is at rest. The screen and glass cover are withdrawn, and a tin cover is 

 placed over all the burners, and rests upon the top of the reservoir, covering 

 the rim perforated with air-holes. This tin serves as an extinguisher, it pre- 

 vents the spontaneous evaporation of the spirit, it protects the platina balls 

 from injury, and preserves all clean. The whole of the tin-work is japanned 

 externally. 



When an experiment is about to be performed, the tube G. is taken off, 

 then the screen H., afterwards the glass cover F. The wicks are then to be 

 saturated, by dropping stronger alcohol upon each of them, after which they 

 are to be lighted ; in a few seconds the platina balls become red hot, the flame 

 is then blown out, the retort with its contents is fixed on the brass stand, 

 which is placed within the circle of the twelve burners. Then the glass cover, 

 screen, and tube, are replaced as before. 



The best and neatest mode of setting the apparatus into operation, is to 

 render each of the platina balls incandescent, by means of the blowpipe and 



