:g(f^ History of Mechanical Inventions and 



into the form of a siphon, and suspended so that its ends may 

 be immersed about half way in the water in the two vessels. 



This siphon is furnished with the stop-cocks F and F\ near 

 the ends, and the filling cock G on its highest part. The end 

 in the vessel A is bent with its orifice upwards, which should 

 still be several inches below the surface of the fluid. This is 

 done to prevent the air bubbles, that arise from the bottom of 

 A, when heat is applied, from going into the tube, and lodg- 

 ing in its upper part. 



In order to prepare this apparatus for action, (water being 

 put already in the two vessels A and B,) istop the cocks F and 

 F' ; open G ; and with a funnel fill the tube with water, until 

 it overflows : stop G, and open F and F^ ; the air below F and 

 F' will immediately rush upwards, and be replaced by water. 

 Stop F and F'', open G, and pour in more water, until the 

 tube be again quite full ; and, in most cases, where air plugs 

 are not necessary, the whole will be fit for action. Should 

 any doubt, however, remain, that the air is not all excluded, 

 the process of stopping G, unstopping F and F', and filling, 

 must be again and again repeated. * 



When the Thermosiphon C C is full of water, stop G, open 

 F and F^, and also the cock E in the connecting tube ; apply 

 the fire to A, and the water will almost immediately begin to 

 circulate through C C from A, to B ; and return, by the con- 

 necting tube D, to A, for a fresh supply of heat : and as the 

 heat of the water in A increases or diminishes, so the circula- 

 tion will be faster or slower. 



The rationale of this process is : — first, it is evident that 

 the water, or other fluid, is kept up in the Thermosiphon by 

 pressure of the atmosphere on the surfaces of the fluid in the 

 two vessels. Secondly, the connecting tube D keeps the cold 

 fluid to a perfect level in those vessels : also, when the tube 

 F, G, F, is filled (should its height not exceed the limit of at- 

 mospheric pressure) it forms a communication between the two 



* The extreme height of G must be regulated generally by the specific 

 gravity of the fluid, and the degree of heat required. I find, by experi- 

 ment, that when G is twenty feet high, water will rise and circulate through 

 a tube sixty feet in length, and f inch diameter, and produce a tempera- 

 ture of from 140° to 150° in B, particularly when the best form is adopt- 

 ed. 



