On Vie Camposition and Becomposilion of Forces* 323 



the pptas§ tube till ne^r the end of the process, bring it to 

 a red' heaf, before any of the alkali is supplied; then the 

 iron turniuj^s being at a white heat, I introduce pieces of 

 the potass in succession : these arc immediately brought 

 into igneous fusion, adniitting of part of the water contained 

 in it to pass oOT, and in this state it drops down on the 

 iron. When the last portion is introduced, and this also 

 is hocome red hqt, the stopper is put into the tube and 

 luted over. This is all done m less than ten minutes, froni 

 the first supplying of the potass tube with alkali: at th^ 

 other end a glass tube passes down into some olive oil : 

 here the hydrogen escapes, often in a siate of brilliant com- 

 bustion, and potassium deposits in the glass tube : this 

 however should be prevented by wet cloths applied to the 

 straight part of the gun -barrel. 



Description of the Drawing (Plate IX.) 



A. Potass tube. 



B. Stopper to be put in at the end of the process. 



C. The situation of the iron turnings. 



D. The fire-place. 



E. The grate. 



F. The pipe of the bellows. 



G. Straight part ground to the bent part. 



H. Thin iron tube to be placed within the joint, to collect 

 the potassium. 



I. Glass tube. 



K. Olive oil. 



L. Tht part where the gun-barrel begins to decline down- 

 ward. N. B. This inclination should commence 

 precisely at the point where the tube emerges from 

 the furnace, to prevent the potassium from flowing 

 back on the iron turnings. 



M. Stop-cock screwed into a socket fixed in the gun- 

 barrel, which is shut the moment gas ceases to be 

 given off, and which is known by tlte consequent 

 absorption*. 



^IV. On the Composition and Decomposition of Forces, 

 Translated from '' Traitc elcmentaire de Staiique, par 

 Gaspard MoNGEj" by Mr,W» Marrat, of Boston^ 

 Lincolnshire^* 



\, When a force P, (fi^. 1 and 2,) applied to a deter- 

 Ujiined point .C, of the solid body AB, draws, or pushes 



* Coramunicated by Mr, Marrat. 



X 2 this 



