460 Intelligence and Miscellaneous Articles. 
In all cases the solution of glycerine showed the greater frictional 
and electrical resistances. 
The second experiment was made by dissolving 50 gr. ZnS0 4 
+ 7H 2 in water to a volume of 500 c. c. ; and on the other hand 
50 gr. of ZnS0 4 was dissolved in a little water, and made up to 
500 c. c. by glycerine. 
It was not possible to dissolve zinc vitriol directly in glycerine, 
because glycerine first of all withdraws water from this salt, and 
the salt with a smaller quantity of water of crystallization dissolves 
with difficulty in glycerine. 
In this case the ratios were : — 
Frictional resistance 1 : 86-2 ; Electrical resistance 1 : 109. 
The above numbers show throughout that no proportionality 
exists between frictional and electrical resistance ; but that the 
solvent has a predominant influence in the processes in question. 
It follows moreover that the more concentrated are the solutions 
the less predominant is the influence of the solvent. 
Leipzig, August 1883. 
SPECTKOSCOPIC NOTES. 
BY PKOFESSOR C. A. YOUNG, PRINCETON, N. J. 
For the past few months I have been examining the spectra of 
sun-spots with great care, and with an instrument of high dispersion. 
The spectroscope employed consists of a comet-seeker of five inches 
aperture and about forty-eight inches focal length, used both as 
collimator and view-telescope after Littrow's method, the slit and 
diagonal eye-piece being as close together as it is convenient to 
place them. A small spot of black paper, about three tenths of an 
inch in diameter, is cemented to the centre of the object-glass 
(as suggested by my colleague, Professor Brackett, in a note 
published in the American Journal of Science, July 1882), and 
entirely destroys the internal reflections, which would otherwise 
most seriously interfere with vision. 
The dispersion is obtained by one of Professor Bowland's 
magnificent gratings on a speculum-metal plane, with a ruled surface 
three and one-half inches by five, 14,000 lines to the inch. The 
slit and eye-piece of the telescope are so placed that the line joining 
them is parallel to the lines of the ruling. An instrument of this 
sort is incomparably more convenient than one in which the 
collimator and view-telescope are separate, though of course, on 
account of the inclination of the visual rays to the axis of the 
object-glass, there is a little aberration, and the maximissimum of 
definition is not quite reached. There is no difficulty, however, in 
seeing easily the duplicity of the b's, E r and other similar tests 
with the instrument thus arranged. The spectroscope is mounted 
upon a strong plank, stiffly braced, and this is attached by powerful 
