334 History of Mechanical Inventions and 



seven pages, and contains not only the fullest practical details, but a learn- 

 ed mathematical investigation of the theory of the instrument. 



This instrument was too ingenious not to excite attention in England, 

 and Mr Nicholson, one of our most learned and ingenious editors, published 

 a full account of it, with all Captain Say's figures, in the first volume of 

 his quarto Journal of Natural Philosophy , a work to the third volume of 

 which Professor Leslie was himself a contributor. 



We hope that those who, without happening to know of the invention 

 of Captain Say, have ascribed it to another person, will yet do justice to 

 the memory and talents of that able, but unfortunate soldier. 



art. xl—history of mechanical inventions and 

 processes in the useful arts. 



1. Mode of Heating Water for a Bath. By Edward Deas Thomson, Esq. 



By means of the following contrivance, Mr Thomson has obtained a bath, 

 containing forty gallons of water, at a temperature of 98° Fahr., in half an 

 hour from the time of lighting the fire, and with only 7 lbs. of coal. 

 The whole expence was 2£d. or 3d., exclusive of the tear and wear of the 

 apparatus. 



A cylinder cc, Plate IV. Fig. 8, eighteen inches high, and nine inches in 

 diameter, is surrounded by a spiral pipe at least an inch distant from it. 

 This pipe communicates with the cistern a above the apparatus by the 

 pipe bb, whose other end descends into the cylinder at c, The water con- 

 sequently passes from the cistern through bb into the cylinder, and thence 

 through the pipe d into the bath. When the cock/ is opened, hot water 

 will flow from the cylinder through d into the bath, and its place will be 

 instantly supplied by cold water through bb, a constant current of water 

 being thus kept up through the boiler cc, which becomes heated in its 

 passage. The degree of heat may be regulated by partially shutting or 

 opening the cock/. An open safety-pipe e rising above the level of the wa- 

 ter in the cistern, allows the steam to escape in 6ase of the water boiling 

 when the cock/ is shut. 



If we suppose the pipe b to terminate in the bath, and the bath to rise a 

 little above the level of the pipe/ the cistern maybe dispensed with. In 

 this case cold water must be poured into the bath till it rise above the level 

 of the pipe/ The water heated in the boiler will then flow into the bath, 

 and its place be supplied by cold water, thus forming a continued current 

 till the whole is heated to the required temperature. — Phil. Man;, No. i. 

 p. 10G. 



2. Process of Separating Elaine from Oils.* By M. Pechet. 



This process is founded on the property which a strong solution of soda 

 possesses of saponifying stearine in the cold without acting upon elaine. 



* See this Journal, No. vi. p. 350. 



