Hydro-electric Machine. 195 



The powerful effects which I obtained in the autumn of 

 last year, with the electric boiler which I then used, induced 

 me to offer to procure one to be made, of a large size, and 

 upon an improved construction, for the Polytechnic Institu- 

 tion in London. My offer was accepted, and the apparatus, 

 which, in conformity with your theory, I shall in future call a 

 " Hydro-electric Machine," has recently been completed, and 

 will shortly appear at the Institution for which it is destined ; 

 where I hope, with proper arrangements for carrying off the 

 discharged steam, it will act as well as it has done in the 

 open air. 



I shall now endeavour to give you a general idea of the na- 

 ture of the apparatus, and will then proceed to speak of its 

 effects. 



The boiler is a cylinder made of rolled iron plate, and 

 measures three feet six inches in diameter, and six feet six 

 inches in length, exclusive of the smoke chamber, which forms 

 an extension of the cylinder, and makes the extreme length 

 seven feet six inches. The fire-place is contained within the 

 boiler, and the heated air is conveyed through the water, in 

 tubular flues, to the smoke chamber, to which a chimney is 

 attached. The apparatus is supported, at a height of three 

 feet from the ground, upon six strong pillars of dark green 

 glass, which insulate it very effectually ; and the steam is dis- 

 charged from forty-six jets, to each of which it is conveyed 

 through an iron condensing pipe, in which the cold of the ex- 

 ternal air causes the deposition of the proper proportion of 

 water to be ejected with the steam. 



Fig. 1 represents one of the jets. It consists of a brass 



Fig.l. 





socket containing a cylindrical piece of partridge wood, with 

 a circular hole or passage through it one-eighth of an inch in 

 diameter, into which the steam is admitted through an aper- 

 ture, similar to that which I have minutely described in the 

 Philosophical Magazine of January last. [S, 3.vol.xxii. p. 1.] 



O 2 



