NEW STEAM DIGESTIR, 1(>3 



I had by this contrivance,* in a great meafure diminiflied the 

 inconveniences, yet the intermediate ring remaining in the 

 veflel, and the increafed difficulty of executing a more com- 

 plicated inftrument, urged me to attempt forae other more ex- 

 peditious mode of clofing. 



I ftiould almoft be afliamed to confefs that the moft fimple simple and mod 

 and, as I preCume, tiie be(> contrivance of all, did not occur accurate clofurc. 

 to me before I had tried the more complicated ones ; if many 

 refpedtable examples had not proved that the eaiieft and ftiorteft ^ 

 method is often the moft difficult to find. The reafon is obvi- 

 ous: Simplicity, like truth, is only one; the bye paths of 

 error are ipnumerable. 



This method confifts in making the cover fimply an oblong, Defcrlptlon of 

 fquare, or oval plane brafs plate^ accurately ground againft the the fame. It it 

 inferior furfaceof a (imilar frame of the fame metal, fixed and fitsagainft a 

 foldered to the opening of the digefter. This frame has an Surface within* 

 oblong aperture, through which the cover may be put in or 

 taken out at pleafure. When put in and prefTed gently againft 

 the frame, it will by the means of a little oil,^ have adhefion 

 enough to bear its own weight, till the fteam begins to a6t, 

 which will clofe it perfe<5lly. But for greater fecurity afmall 

 piece of wood, fixed with a fcrew, will keep the plate joined 

 to the frame, and ferve at the fame time as a handle. Fig. 1» 

 Plate IX. reprefents the longitudinal feflion of the whole in- 

 ftrument, with all its parts; abh the covering plate, ground 

 and fitted agaiuft a fquare metallic frame cd, foldered X to the 

 veflel at c/, which ought to be made of hammered copper at 

 leaft If line thick. Fi^, 2 is the tranfverfe fedionof the fame 

 apparatus, and Fl^, 3. a plan of the brafs plate, where the dot- 

 ted lines mark the opening of the frame c d, Fig. 1 . and the 



* The digefter with a conical plate, and the fafety-pifton defcribed 

 below, firft executed in Stockholm, 1793, was exhibited to the 

 members of the Royal Society in Berlin, in Feb. 1802j and a de- 

 fcriptioitvof it, printed in the Obfervations Phyliques of Mr. Dela- 

 metherie, Feb. 1803. 



t The different force of adhefion of the fame metal, in employ- 

 ing different oils, is remarkable, and may afford a field for future 

 ^nveftigation. 



X Befides foldering, the parts Ihould be joined together with rivets 

 9v fcrcws. 



M 2 pjtrt 



