NEW STEAM DIGESTER. 16S 



«J<!gree of heat is eafily obferved on the ftem. This degree 

 will not be exadly the fame with that of the interior fpacej it 

 fliews always fomewhat lefs, which fa6t was long time ago ob- 

 served by Mr. Brauii of the academy of Peterfburg; but the 

 difference is fmall, and being once afcertained, by experiment 

 made on purpofe, a due corre6lion, by adding that difference, 

 is eafily made. 



The heat is communicated in my apparatus by a common The heat gWca 

 Argand^slamp, which was always found fufficient and of which ^ * ^^^' 

 the effedl may be regulated by the pinion of that inflrument. 

 If time be an objedi, or if the digefler is much more than 

 double the fize of Fig. 1 . the fcale of which is one third of the 

 real fize, two fuch lamps may be applied. But a lamp with 

 fpiritof wine and three wicks will fupply fire enough for a tem.- 

 perature of 270 or 280 if the digefler be fmall and exaftly 

 clofed. As the atmofphere continually takes away a part of 

 the heat communicated to the veffel, ii is only the diflerence of 

 the communicated and diffipated heat which a6ls on the fleam, 

 and determines the limits of its force, when the fire is weak, 

 and the digefter of a large fize. On the other fide, the heat Thehcitiscon- 

 of the interior fluid an4 the elaflicity of fleam correfponding to preffing weight 

 it, cannot, after having lifted the piflon, be encreafed by a be not changed, 

 continued fire or by a greater number of lamps, but remains 

 from that moment conftant, which feems to be a particular 

 property of this conftruftion. A farther increafe of heat, as 

 the 2d. defideratum, can only be obtained by oppofang a greater 

 refinance to the adion of the vapour beneath the furface k, 

 which is performed by loading the piflon with one or more of 

 the weights r r, Fig. 1 . Thus we may either add new weights 

 progrefTively, till the thermometer indicates the degree of heat 

 required, or knowing by the former experiments of philofophers 

 the correfponding ratio of increafed preffure and heat of elaflic 

 fluids, we can load the piflon at once with a weight propor-» 

 tional to the intended heat and the furface of its bafe k. This 

 will then rife as foon as that degree is produced, and allowing 



the (leam to efcape from one or more of the holes * prevent What is the 



fecond condw 

 ♦ By what is faid above it is evident that the height of the piflon, ^*°"* 

 #r the number of the holes open to the fleam, is of no confequence, 

 it being always compreffed by the fame weight, and a6lingwith the 

 fajnc e^afticity. The aufntitj produced is only different, 



any ♦ 



