48 



Professor W. A. Bone 



[Feb. 27 



I need hardly point out to you the many obvious purposes, 

 domestic and industrial, to which " diaphragm heating " may be 

 applied. In the domestic line, the boiling of water, grilling, roasting 

 and toasting are at once suggested, and although the best existing 

 types of gas fires are thoroughly hygienic and efficient, I think that 

 the diaphragm may come in for the heating of apartments ; at any 

 rate experiments are being carried out in that direction. 



I have recently been told of a large restaurant in London where 

 they are grilling by means of an electric radiator fixed horizontally 

 above the work so that the radiant energy is directed downwards on 

 to it. It has been claimed that the value of the recovered fat, which 

 in the ordinary method of grilling drops into the fire and is consumed, 



Fig. 4. — Diaphragm for Boiling Sugar Solutions, Etc. 



has more than paid for the electricity used. With a diaphragm, 

 similar advantages can be secured with gas at a considerably less 

 cost ; for comparing gas of net calorific value 500 B.Th.Us.^^ per 

 cub. ft. at 2s. Qd. per 1000 cub. ft. with electricity at M. per unit, 

 the initial cost of a given amount of energy is about 14 times greater 

 in the form of electricity than in the form of gas. 



Turning now to the industrial field, I had the satisfaction of 

 visiting not long ago a large confectionery factory where the dia- 

 phragms have been employed for more than a year for the boiling 

 and concentrating sugar solutions. The solution is boiled in a copper 

 pan over a 13-in. diameter circular diaphragm (see Fig. 4) ; the 



