4l6 PHILOSOPHICAL TRANSACTIONS. [anNO I7O8. 



eluded brass leaf. Yet at the same time I must believe, that the particles of 

 the glass are then in a greater motion, than when the experiment will not suc- 

 ceed. What I farther observed was, that the effluvia of the wax may very 

 sensibly be felt on the back of the hand, the wax being moved to and fro near 

 it ; as I have formerly observed the like sensible strokes given by the effluvia of 

 glass. 



j^n Experiment showing the (liferent Densities of the ^ir, from the Greatest 

 Natural Heat, to the Greatest JSatural Cold, in this Climate. By Mr. Fr, 

 Hauhsbee, F. R. S. N° 3i5, p. 93. 



I took a glass tube about 2 feet long, and near 2 tenths in diameter; which, 

 at about 6 inches from one end, I bent in form of a syphon, as represented in 

 fig. 20, pi. 10: at whose farthest extremity I cemented a brass screw, with a 

 small perforation in it; by which means, when I put a little quicksilver into the 

 shorter leg, I could, by declining the tube, or longest leg, bring it to rest any 

 where; as suppose at a, the superfluous air within passing through the said 

 perforation. Then screwing a cap on it, the mercury was detained in the same 

 place, and occupied about half an inch in length. In this manner it was con- 

 veyed into a wooden trough, with a thermometer: then putting in as much 

 warm water as would cover its ball, the syphon lying at the bottom in a horizon- 

 tal position, its shorter leg appearing above the water, (which was so contrived 

 as to prevent any inconvenience that might arise by the water's getting into it, 

 and to give a free liberty for the pressure of the outward air to exercise its full 

 power) ; when the spirit of wine had ascended by the heat of the water into it5 

 small ball at top, which I thought was necessary, that I might make my obser- 

 vations with the more exactness on its descent ; supposing by that time it should 

 fall to the degree designed to begin at, that the spirit in the ball would have re- 

 ceived an equal degree of heat in all its parts. Accordingly, I began my obser- 

 vations when it had descended to 1 30 degrees above the freezing point ; at 

 which time I found the length of the column of air, from the closed end of the 

 syphon, to the nearest surface of the quicksilver, to be just 144 tenths of an 

 inch. After the spirit had descended 10 degrees lower, the air, which before 

 possessed 144 parts, was now one part less; and so on successively, at every 10 

 degrees descent of the spirit, the column of the contained air was lessened in its 

 length exactly one tenth. When it had descended to 30 degrees above the 

 freezing point, the air was found to possess only 134 of the said parts: so that 

 from hence it will be easy to conclude, that at the freezing point, the air in the 

 lyphon would be reduced to 3 tenths less than the last observation. Con- 



