\6G NEW STE"^M DIGESTER. 



any further Increafe of the heat, which will remain invariable 

 as the third defideratum required.* 

 Very great d!f- Here it feems proper once again to infift upon the great ira- 

 fmperfeft do- P^^'^^^ce of a perfea clofure in this inftruinent. IF the heated 

 fure of the di- fteam, by inaccuracy in the conftru6lion, is permitted to 

 gcftor. efcape, not only a great part of the contents is wafted with- 



out any ufe, before the experiment can be faid to begin, which 

 fometimes obliges us to open thedi^efter and fill it a fecondtirae, 

 but even fome of the materials may be altered and decompofed 

 before the intended effed can take place. Still more, very 

 often in fuch cafes, a flrong kitchen fire, with the greateft 

 exertions of the operator, (not to mention the trouble and 

 inconvenience of fuch an operation) is infufficient to afford 

 the degree of heat, which a fmgle lamp, placed with the ap^ 

 paratus on a fmall writing table, would produce with eafe, and 

 without wafte of the materials. 



In the prefent ftate of natural philofophy, the progrefs of 

 the fcience feems to depend in a great meafure on theperfedion 

 -of our inftrnments. In this point of view the precedingattempts 

 to render a little ufcd but very excellent machine more fafe, 

 exa^, and convenient f, may, if it (hould not anfwer that pur- 

 pofe, at leaft give rife to other more fuccefsful improve- 

 ments. 



• A fliort defcrjption of this contrivance was prefented to the 

 Philofopbical Magazine in June, 1803, and publiftied in December 



' the fame yearj but by the ufe of the word pi/o» inftead of di- 



gejier in a note, an erroneous .ftatement is given in the printed 

 account, which, however trifling it may appear, it is proper to cor- 

 real, as this part of the inftrument has not been changed at all, fuicq 

 it was firft made and known in Sweden ten years ago. In the 

 fame paper I propofed the ufe of it for regulating the fire in boilers 



' of fteam engines, &c.— and its efFe(5V as a regulatory both of the 



poiver cf the feam, and the intenfity of the fircy depends entirely 

 upon the ^weight being conftant and wi/ariable in the whole motion 

 of the pifton, 



f Digefters, as defcribed in this paper, are made by lyir. FiDLER, 

 tn:ithematical inlhument maker, 23, Oxford-market, London. 



II. Inveji.'gatioit 



