ROBERT BOYLE 51 



ing thrust down into the greater tube almost filled with quicksilver, 

 the glass helped to make it swell to the top of the tube; and the 

 quicksilver getting in at the lower orifice of the pipe filled it up till 

 the mercury included in that was near about a level with the surface 

 of the surrounding mercury in the tube. There being, as near as 

 we could guess, little more than an inch of the slender pipe left above 

 the surface of the restagnant mercury, and consequently unfilled 

 therewith, the prominent orifice was carefully closed with sealing-wax 

 melted; after which the pipe was let alone for a while that the air, 

 dilated a little by the heat of the wax, might, upon refrigeration, be 

 reduced to its wonted density. And then we observed, by the help 

 of the above-mentioned list of paper, whether we had not included 

 somewhat more or somewhat less than an inch of air; and in either 

 case we were fain to rectify the error by a small hole made (with 

 a heated pin) in the wax, and afterward closed up again. Having 

 thus included a just inch of air, we lifted up the slender pipe by 

 degrees, till the air was dilated to an inch, an inch and a half, two 

 inches, etc., and observed in inches and eighths the length of the 

 mercurial cylinder, which, at each degree of the air's expansion, was 

 impelled above the surface of the restagnant mercury in the tube. 

 The observations being ended, we presently made the Torricellian 

 experiment with the above mentiond great tube of 6 feet long, that 

 we might know the height of the mercurial cylinder for that par- 

 ticular day and hour, which height we found to be 29^ inches. 



