Greater Influence of First Quantities of Electrolytes* 483 



placement of the iron lines in the spectrum of the metal would 

 result. There would be both a displacement . toward the less 

 refrangible end caused by the recession of the atom, and one 

 toward the more refrangible end of the spectrum caused by 

 the approach of the atom. The great amount of dispersion 

 afforded by a concave grating of 20,000 lines to the inch 

 enabled me to easily detect a movement equivalent to a tenth* 

 metre. I accordingly took a photograph of the iron lines 

 with the terminals in the position I have described, and on 

 the same plate immediately above this photograph a com- 

 parison photograph was taken with the terminals paralled to 

 the slit. In this case the iron atoms did not make their sup- 

 posed excursions away and toward the slit, and therefore no 

 displacement of the spectrum-lines was to be expected. 



The photographic plate was exposed in the neighbourhood 

 of the great H -lines. A movable shutter enabled me to 

 expose different portions of the same plate without changing 

 any adjustments of the apparatus. The resulting photographs 

 showed no displacement of the iron-lines. The iron-lines in 

 the two photographs met exactly (continued in an unbroken 

 line across the double photograph), and were of the same 

 breadth throughout their extent (see figure). 



The conclusion seems to be a strong one that the electrical 

 oscillations do not carry the atoms of metals with them — in 

 spark-discharges. The atom is merely shaken up and caused 

 to emit the vibrations or subsidiary ripples which appeal to 

 our senses as light and heat, while the electrical waves pass 

 on without conveying the atoms. 



Jefferson Physical Laboratory, 

 Harvard College, Cambridge, U.S. 



LV. The Greater Influence of First Quantities of Electrolytes 

 on Volta-Electromotive Force. By Dr. G. Goke, F.R.S* 



IN thermochemical research, Favre and others observed 

 that, on adding equal quantities of water in succession to 

 a fixed amount, either of nitric or sulphuric acid, the quantity 

 of heat evolved was greater with the first than with any 

 succeeding dilution (Watts' s ' Dictionary of Chemistry/ vol.iii. 

 p. 310) ; and similar effects were noticed by J. Thomsen on 

 diluting concentrated hydrochloric, hydrobromic, and hydri- 

 odic acids. Nicol has observed that the total contraction of 

 volume of a saline solution increases with the proportion of 

 dissolved salt, and that each successive equivalent weight of 

 the salt produces less contraction. Kohlrausch and others 



* Communicated by the Author. 



