SCIENTIFIC SUMMARY. 
215 
"between platinum poles, copper (as sulphate) travels to the — electrode, but 
not in sufficient quantity to replace that which is there deposited (Hittorf, 
Wiedemann). 
Kemembering the molecular indifference which crystalloids and colloids 
hear to one another, the question presented itself : — Is there, in a mixture of 
the two kinds of matter, sufficient continuity and mobility amongst the 
crystalloid molecules to establish an electric chain P If there be so, — mole- 
cular currents being wholly suppressed by the colloidal obstruction, — a 
valuable means would be furnished for tracing the “ wandering of the ions.” 
Water was boiled with sufficient gelatine to form a stiff jelly. In this, 
while warm, a little sulphate of sodium was dissolved together with some 
litmus. To one portion a drop of dilute sulphuric acid was added, to another 
a drop of ammonia. When the jellies had set in glass cells, pairs of sheet 
platinum electrodes nearly fitting the cells were thrust in, about two inches 
apart in both cases. Six pint platino-zinc battery cells were attached to 
each (in succession). Flattened bubbles of gas forced themselves up from 
both poles with a crackling noise. In a quarter of an hour, in the slightly 
reddened cell, both faces of the + electrode were clothed with a brighter and 
more transparent red envelope, but somewhat thicker towards the other 
electrode. The — electrode was coated with a transparent blue envelope. 
These two conditions spread and met one another in about three-quarters of 
an hour, in a vertical plane between the two electrodes, somewhat less than 
twice as far from the - as from the + electrode : the blue band being the 
■widest. This plane was maintained for three hours after its establishment 
with the current in action, and kept the same for days after the current had 
been broken ; although by automatic diffusion, the blueness and redness have 
spread backwards. A similar effect was produced in the blue jelly. The 
heat developed produced a slight fusion, which was confined to the - elec- 
trode. F. Guthrie. 
A Point in the Theory of Brass Instruments . — A paper was read before 
the Physical Society, by Mr. D. J. Blaikley, on this subject. The common 
description of such instruments as cones, or cones combined with cylindrical 
tubing, was objected to as being inaccurate, as was also the opinion that 
horns, trumpets, &c., have naturally, of necessity, just intonation, or notes 
with vibrational numbers, 1, 2, 3, 4, &c., corresponding to the prime, octave, 
twelfth, double octave, &c. The two simple forms of resonators that give 
these intervals, the open tube of equal section and the complete cone, were 
shown, and the positions of their nodal points explained. The positions of 
the nodes in the cone were experimentally determined by a method which is 
believed to be new, and is peculiarly applicable to tubes of varying section. 
The conical or other tubes, the nodes of which were to be determined, were 
immersed in water, until the length giving the maximum resonance to a 
vibrating fork of the required pitch, held over the tube, was fixed by the 
water level. It was then shown that the action of the lips does not, at least 
to any material extent, affect the conditions of resonance. Various truncated 
cones, with and without the addition of cylindrical tubing, were then blown 
by the lips ; none of them gave the required harmonic intervals, and it was 
demonstrated that this was because the position of the lips did not correspond 
to that of a nodal point common to all the points required. The positions of 
