24* 



PRIMARY ANtMAL FLUIDS, 



fedly as can be defired, being prefled by the united ehdictif 

 pf the rpring and the fteam. 

 The fame applied fig, 4.. is the fame contrivance adapted to a new kind of 

 'ffifitj/ valve or pijioiif which, though I originally intended H 

 for the uTe of Papin's drgefters of a new conflrudion *, has 

 been, in a larger fize, applied by me even to fleam engines, 

 and is defcribed in the Philofophical Magazine of Decem- 

 ber, ISOS.f 



I have lately begun^ and fliall purfuc, a fet of experimenls, 

 with the intention of regulating by this fafety pifton, the 

 quantity of admitted air to fire-grafes, and to elTecl, by that 

 means, a new mode of regulating Hie fire, and the elaflicity 

 of fteara in boilers, with lefs expenditure of fuel and of force 

 than ufual ; of which idea a hint is given in the work and 

 place above mentioned. The refuit of thefe refearches 1 

 fhall at fome future period do myfeif the honour of communi- 

 cating to the Society, 



^ivance. 



Other experi- 

 ments. 



IV. 



Ol/trvfitions and Experiments for the Piirpoje of afcertuinin^ 

 the dtfinite Ckaractcns of the primary Animal Fluids, aud to 

 indicate their preftnce by accurate clmnical Tcjls. i?j/ John 

 BosTOCK, M.D, Ccmimunicatcd by the Author, 



Great want of i. HE preclfion which the analyfis of mineral and vegetable 

 Sn^malanalyfis^ ^^'^^^"^^s ^^^^ attained, docs not appear to be yet extended to 



fuirticutarly of 



the fluids. * Nicholfon's Journal, March, 1804. 



f The defcription of this contrivance being already publifhed, 

 it would be fuperfluous to repeat it. I only beg leave to add ths 

 following practical remark. A metallic pifton, if well turned and 

 * fitted into a cylinder of exaftly the fame kind of metal, will pro- 



bably have the fame degree of expanfion, efpecially if hollow, and 

 confequently will not increafe its fri6lion in any increafed degree 

 of temperature. But as in praflice, the cylinder is commonly ex- 

 pofed to a lower temperature than the pifton, heated by the fteam, 

 a little increafe of friftion will take place by an increafe of heat. 

 To prevent the effeft ©f this, I have found it ufeful to employ for 

 the pifton a metal of fomewhat lefs expanfive power than the cy- 

 linder; and the expanfion of red copper being to that of biafs 

 nearly as 10 to 1 1 , I prefer making the piftan of the former metal; 

 when the cylinder is made of brafs. 



Ihe 



