ON EVAPORATING FURNACHS, ] jy 



General Remarks on the ConJlru6tion of Furnaces, 

 That part of the fire-place which is to fupport the greateft 

 heat, ftiould be made of very refractory bricks. The beft ce- 

 ment or mortar for bricks, in all cafes where a bad condu6tor of 

 heat is required, is a mixture of equal parts by meafure of tan 

 and clay. The tan prevents the cement from cracking, and 

 produces an adhefivenefs which, when dry, gives it a great 

 <legree of firmnefs. 



Furnaces may alfo be conftru6led with this mortar, and on 

 the fame principles with thofe of evaporation, which I am about 

 to defcribe. 



Furnaces intended for flrong heat, fliouM Jje externally co- 

 vered with a thick wall, conftru6led with the mortar of tan. 

 By this means very little heat will be loft. All furnaces (hould 

 be fo conftrufled as to have the power of clofing the upper 

 aperture of the chimney at pleafure, in order to check the 

 combuftion, and concentrate the heat within the furnace, when-r 

 ever this becomes neceflary. When the temperature is very 

 high, it is particularly necelTary to regulate the ifFue of the 

 current of air fo as to prevent its too fpeedy circulation through 

 the furnace, which, in certain cafes, is prejudicial to the fuc;- 

 cefs of the operation. 



By uniting all thefe conditions in furnaces, a certain faving 

 of one fourth of the fuel will be made, and the combuftion 

 will be produced without any appearance of fn>oke. 1 infift 

 more particularly on this remark, becaufe it is clearly and phy- 

 iically proved that no combuftible can be completely burned 

 if fmoke be produced. 



DefcriptioH of an Evaporating Furnace, in tvhich the Temperature 

 may be raifed at Pieajure. 



For common furnaces, the aperture of the vault A, Plate DefcriptSoa ©f 

 VI. rtiould be four decimetres (1.5| inches) wide, by three ='^"'"^'=5 ^'^'^ 

 decimetres and a half (13| inches) in height; B is the part of 

 the vaul,^' in which the combuftion is performed. This vault 

 muft be at/leaft two metres [6\ feet) in length. C reprefents 

 a boiler of one metre and a half (nearly five feet) in diameter, 

 and of the lame depth; it is fet in a brick furnace. 



The interval from the bottom of the boiler to thebafe of the 

 furnace muft be at moft one decimetre (about four inches.) It 

 muft be obferved in the conftrui^ion of furnaces, that the bricks 

 work (hould be gradually floped towards the boiler, and to re- 

 duce 



