and in the Condensation of Vapours. 373 



copper rim, three lines deep, which is fastened by a row 

 of very small nails to the wooden frame. The body of 

 the receiver itself enters about a line into the frame, to 

 which it is very accurately fitted. 



The flat form of the worm is essential to the. perfec- 

 tion of the apparatus, as is evident when its purpose is 

 considered. 



All the products of the combustion being elastic 

 fluids, and consequently substances incapable of com- 

 municating their heat but by proceeding particle after 

 particle to deposit it on the surface of the cold and 

 fixed body intended to receive it, it was indispensable so 

 to construct the apparatus that the hot fluids should of 

 necessity be spread beneath and against a large flat sur- 

 face, placed horizontally, and always cold. 



Before I employed horizontal worms made of flat 

 tubes, I had more than once tried those of the common 

 form ; but they never answered my purpose otherwise 

 than so imperfectly that I could never make any account 

 of the experiments in which they were employed. 

 There is no doubt but the shape I have adopted for the 

 worm of my calorimeter would be very advantageous 

 for every kind of apparatus for distillation. 



One thing very important in the construction of my 

 apparatus is the shape of the thermometer which I 

 employ to measure the temperature of the water in the 

 receiver. This thermometer which I made myself, and 

 which, after having undergone every kind of trial, has 

 always appeared good is a mercurial thermometer, 

 divided according to Fahrenheit's scale. It is one of 

 four, all similar, that I employed at Munich, in the 

 winter of 1802, in my experiments on the refrigeration 

 of liquids enclosed in vessels. 



