1876.] 
373 
at South Kensington. 
No. 8 is an apparatus used for the determination of the 
tension of volatile liquids at low temperatures ; it consists 
of a syphon tube, at the upper end of which is a scale in 
inches in Dalton’s handwriting. He describes it thus: — “I 
took a barometer tube 45 inches in length, and, having 
sealed it hermetically at one end, bent it into a syphon 
shape, making the legs parallel, the one that was closed 
being 9 inches long, the other 36 inches. I then conveyed 
two or three drops of ether to the end of the closed leg, and 
filled the rest of the tube with mercury, except about 
10 inches at the open end. This done, I immersed the 
whole of the short leg containing the ether into a tall glass 
containing hot water.” 
No. 9 is a smaller tube containing another liquid, also 
having a graduated scale written on paper and attached to 
the tube. 
Nos. 10, ir, 12, 13, 14, are tubes used by Dalton for mea- 
suring the tension of vapour from water and other liquids 
at higher temperatures than their boiling-points, both in a 
vacuum and air. 
No. 15 is a tube used by Dalton for measuring the tension 
of the vapour of bisulphide of carbon, labelled “ Sulphuret 
carb.,” with a paper scale in Dalton’s handwriting, and a 
cork showing that the upper portion of the tube containing 
the bisulphide of carbon could be heated in a water-bath to 
various temperatures. 
No. 16 is a manometer tube, fixed into a board, divided 
and numbered by Dalton. 
No. 17 is an apparatus used by Dalton for the determina- 
tion of the tension of the vapour of ether, and is interesting 
as being the instrument by means of which Dalton arrived 
at one of his most important experimental laws. It is 
described as follows (p. 564) : — The ether I used boiled in 
the open air at 102°. I filled a barometer tube with mer- 
cury moistened by agitation in ether ; after a few minutes a 
portion of the ether rose to the top of the mercurial column, 
and the height of the column became stationary. When the 
whole had acquired the temperature of the room (62°) the 
mercury stood at 17*00 inches, the barometer being at the 
same time 29*75 inches. Hence the force of the vapour 
from ether at 62° is equal to 12*74 °f aqueous vapour at 172° 
temperature, which are 40° from the respective boiling-points 
of the liquids.” This is generally known as Dalton’s law of 
tensions, since shown by Regnault not to be rigorously true. 
No. 18 is a wet and dry bulb mercurial thermometer made 
by H. H. Watson, of Bolton. 
