OF ARTS AND SCIENCES. 241 



measurements on naphthaline, gave 0.00 366 95 and 0.00 366 87, of 

 which the mean, 0.00 366 91, was employed. Other values are: — 



Regnault 0.00 366 82 



Magnus 367 10 



Jolly 367 28 



Rowland 367 13 



Mean 0.00 367 08 



With this mean the above value is in so close accordance as to show 

 that the apparatus and coefficient of expansion of glass used must be 

 sensibly correct. The formulae used in computing a and temperatures 

 was that given by Rowland.* 



The coefficient of expansion of the glass bulb of the air thermometer 

 was obtained by a weight thermometer made from the same piece of 

 tubing. Both bulbs were made of the full diameter of the original 

 tube, and with no further heating than was necessary to close the ends. 

 They were thus both of the same diameter and thickness, and had 

 been subjected to substantially the same treatment. In the computa- 

 tions, the values of the coefficient /3, used for mercury were those of 

 Wiillner's recomputation of Regnault's experiments. Measurements 

 were made in vapor of benzophenone, naphthaline, aniline, and water, 

 a special double-jacketed heater being employed. The results were: — 



Temp. Pt used. . , 



(Wiillner.) K obta ™ed. 



306 0.00 018 667 0.00 003 004 



306 667 3 012 



218 468 2 895 



184 401 2 830 



100 253 2 700 



The values of * used for the benzol measurements were determined 

 by Mr. W. S. Hadaway, Jr., on glass of the same kind, at temperatures 

 below 100°. The results overlap at 100°, and are sensibly in accord. 

 In some preliminary work, with bulbs carefully annealed before and 

 after having been filled with mercury, values of k up to 218° were 

 obtained which are in close agreement with the foregoing. The bulbs 

 were all filled by boiling the mercury in them. This mercury and 

 that used in the gauges was redistilled in the laboratory. 



The capillary leading from the air thermometer was as fine as pos- 

 sible, and special care was taken to obtain accurately the temperature 

 of the air in the exposed stem of the thermometer. 



* Proc. Amer. Acad., xv. 98 (1880). 



VOL. XXIII. (n. S XV.) 16 



