114 Areometer. 



both open at one end and communicating with each other 

 at their other ends, at which is a small syringe, are intro- 

 duced, the one into water, the other into the liquid to 

 be examined. The air in the tubes is now slightly rarified 

 by means of the syringe, when, by comparing the elevation 

 of the water and of the other liquid in the tubes, the ratio 

 of their specific gravities is given. This is the best of all 

 the instruments for rapidly determining the densit}^, as the 

 influence of temperature and of atmospheric pressure are 

 here almost eliminated."' 



The instrument before you conforms in principle and in 

 general arrangements with the description quoted. We 

 have, yon will observe, two glass tubes, each about three feet 

 long and of very nearl}^ the same internal diameter, namely, 

 three-quarters of an inch. The lower ends of these tubes 

 are open ; the upper ends, also open, are contracted, and 

 fashioned for juncture with caoutchouc tubular couplings. 

 Two wooden rods, each four feet long, are fixed on a stout 

 wooden base, so as to occupy a vertical position with an 

 intervening space of twelve inches between them, and near 

 their tops a light cross piece of wood connects these rods 

 and preserves their parallel position. On the top cross-piece 

 is fixed, in cork mountings, a tubular r^ shaped glass con- 

 necting piece, to each of the two lower openings of which is 

 appended by a caoutchouc junction one of the before-men- 

 tioned vertical glass tubes ; and to the upper opening of this 

 glass junction piece is in the same manner connected a pewter 

 tube, which arches over, is carried down one of the vertical 

 wooden rods, and at its lower extremity, which is again 

 curved upwards, is affixed a caoutchouc syringe — that is 

 to say — a bulb of india-rubber with valves, and which 

 will pump air when alternately compressed by hand pressure 

 and allowed to expand. 



Two matched ordinary glass beakers are placed under the 

 pendant three feet glass tubes, and are blocked up to a 

 proper height by wooden blocks, so that the lower opening 

 of each glass tube is half an inch or less above the bottom 

 of its beaker. A screw-clip is attached to the caoutchouc 

 coupliog over the branched glass tube at the top of the two 

 vertical measuring tubes, and this completes the arrange- 

 ment. 



If mercury be poured into one of the beakers and 

 distilled water into the other, so as to seal off the air 

 contained in the two vertical tubes from direct contact with 



