SECT. II.] 



PROPERTIES OF STEAM. 



67 



It will appear from this, that there is a greater difference between the results of 

 different trials, than between the numbers found by our rule and those results ; and 

 hence it may be presumed to be sufficiently exact. 



98. For the further satisfaction of the reader, the principal results of Dr. lire's 

 experiments shall be given, and his simple and elegant mode of making the experi- 

 ments described ; as, in the event of any other species of fluid being found better 

 adapted than water for furnishing vapour, the same mode might be usefully 

 adopted to try its force. 1 



FIG. 11. 



FIG. 12. 



FIG. 13. 



o 



The preceding figure (fig. 11.) represents the construction employed for tempe- 

 ratures under and a little above the boiling point. Figures 12 and 13 were used 

 for higher temperatures ; the latter is the more convenient of the two. It was 

 suspended from a lofty window ceiling, and placed with the tube L D in a true 

 vertical position by means of a plumbline. One simple principle pervades the 

 whole train of experiments, which is, that the progressive increase of elastic force 

 developed by heat from the liquid, incumbent on the mercury at /, is measured 

 by the length of column which must be added over L, in order to restore 

 the quicksilver to its primitive level at /. These two stations, or points of 

 departure, are nicely defined by a ring of fine platina wire twisted firmly round 

 the tube. 



Philosophical Transactions for 1818. 



