AND RATIO OF TIIKIK ATOMIC; WKIOIITS. 71 



the exposure to wutei- lasted less than two iniiiutes, and solnl»ili(\ of the glass was 

 thonght to be negligible. 



18. IIVDKIHJKN HV NKW MKlUOl). WEIGHING TIIK 'I'UUK ( 'ONTA I NI N(i I>A M.A DI I'M. 



Tile tube eontaining |iMlladiuMi was weighed against: a coiiulerpoise of nearly 

 e(|iial xoliinie and weiglit. Tlie volumes on tlie two pans of the balance were then 

 made eipial within tlie twentieth of a cubic centimetfe by means of the small 

 e((uating tlasks of various volumes but of weights made e((ual if weighed in a 

 vacuum, which were mentioned on page 4.S. The tube of palladium was hung on 

 one of the auxiliary pans of the reversing mechanism shown iu Figs. KJ to lU, on 

 pages 38 to -41, and its counterpoise on the opposite pau, the equalizing flasks were 

 added, and the weights wei'e laid on the pan which carried the palladium. After 

 the closet had been shut for an hour, weighings were made by reveisals just as in 

 the second and third series of determiiuitions of the density of oxygen. Weights 

 smaller than ten milligrammes were not put on the auxiliary pans, but were put on 

 the [)ans of the balance itself ; the fractions of a milligramme were determined by- 

 observation of the value of a scale division and conqiutation from the [tosition 

 of equililirium in the two weighings l)y reversal. Four weighings at suitable 

 intervals were thoUiiht sutHcient; but sometimes time was allowed for more. 



19. 



-UVIUKKiEX UY NEW METUOn. IN rUODUCTION OF llVDKOciEN INTO I'llE (il.olSES. 



The palladium tube was put in an iron trough containing magnesia, and laid 

 on the furnace where it was to be heated. The point /', Figs. 25 and 20, was 

 broken off at the notch previously made, and 

 scrutinized to see if some minute fragment 

 wei'e detached. Air was in this way admitted 

 as far as the [dug <j. To the ground joint /, 

 was then cemented the corresponding joint /, 

 and this was then fused to the tube m n op, 

 Fig. 27, by which hydrogen was to be admit- 

 ted to the globes ; o in Fig. 27 is the same as 

 d in Fig. 2.".. The air-pump w'as then con- 

 nected to n, Fig. 27, the space betweii </ and o was exhausted, and the connection 

 with the pump was closed by fusion. After some few minutes, the fusible metal 

 valve at o. Fig 27, d, Fig. 2o, was opened by fusion ; if the joint at I, Fig. 27, 

 and the fusible valve at </ were tight, the fused metal would not be foi'cibly pro- 

 jecte<l. Before this time the vacuum in the globes hail been measured, and the 



Figs. 26 and 27. — T'.illadium tube, ready to connect 

 to apparatus. I'alladium tube, connected to 

 apparatus, connection exhausted. 



