TRANSACTIONS OF SECTION A. 661 
scarcely be attributed to the greater proportionate share of the current conducted 
by the latter, but is possibly due to some characteristic difference between the 
radiation of metals and non-metals, as also illustrated in flame spectra. 
3. On the Theory of the Electrolytic Solution Presswre. By R. A. LEHFELDT. 
According to Nernst’s theory, when a metal is immersed in an electrolyte a 
minute amount of it goes into solution in the ionic form, giving a positive charge 
to the liquid as compared with the metal, or ions from the solution are deposited in 
metallic form, giving the metal a positive charge according as the osmotic pressure 
of the ions in solution falls short of or exceeds an amount known as the electrolytic 
‘solution pressure. This view has been generally adopted by physical chemists, it 
being supposed that the amount of metal to be deposited or dissolved is too small 
to measure. By combining the calculated value of the solution pressures with the 
known theorems of electrostatics on the tension exerted by electric charges, it may 
be shown, in the case of zinc at least, that the amount dissolved would be some 
centigrammes per square centimetre immersed, and could easily be weighed. 
Hence the theory seems to break down. 
4. Temperature and the Dispersion in Quartz and Calcite. 
By J. W. Girrorp. 
A prism of 30° quartz and prisms of 30° and 60° calcite were used. Measure- 
ments of the deviations of the ordinary ray for W.L. 5892, and of the angle of the 
prism, were made at temperatures from 66° F, to 77°5°. With quartz both 
‘deviations and angles decrease with rise of temperature; with calcite they 
increase. 
If the deviation at any given temperature and the angle observed at that same 
ve _ Daf. 4 Pea 
‘temperature be taken for 7 in the formula sin Dat sin 5, we have a series of 
refractive indices decreasing with rise of temperature for both quartz and calcite, 
of which the following are average instances :— 
Temp. F. \Quartz prism 30°} Temp. F. (Calcite prism 30°} Temp. F. | Calcite prism 60°| 
° ° ° ' 
68:5 15441530 67°75 16584402 65°5 1 6584320 
75:5 154413387 75°25 1°6584029 72:5 | 16584190 
But, if all the angles at all temperatures are added together and the mean 
taken for 7, the following series of indices result :— 
| Temp. F. |Quartz prism 30°} Temp. F. Calcite prism 30°} Temp. F'. | Calcite prism 60° 
° °o ie) 
66 15441638 65°25 16583344 63:5 16583259 
67 15441632 70 16583891 65 16583443 
68 15441616 705 16583983 | 67°5 16583528 
69 1-5441560 74 1:6584305 67-75 16583564 
74:5 15441512 15:25 16584603 69°5 1°6585842 
75 15441307 76 16584929 765 16585075 
755 15441117 
175 15441013 | 
If, omitting the two last of quartz, we deduce the coefficients for unit 
temperature, we have ‘00000868, 0000147, and -0000140 for the three columns 
