480 Intelligence and Miscellaneous Articles, 



small amount of electrolysis by a current of electrostatic origin : 

 experiments which are perfectly consistent with the old electro- 

 chemical theory, dressed up in the garb of the dissociation theory, 

 and then presented to us as proof positive of this theory. 



MEASUREMENT OF THE CHEMICAL INTENSITY OF THE SOLAR 

 RADIATION. BY A. BARTOLI. 



The author raises the objection to previous investigations on this 

 subject, that exothermal chemical processes have in many cases 

 been used in which the heat developed must have a disturbing 

 influence. The apparatus of the author consists of two metal 

 vessels fitting one in the other, the inner one of which has a capacity 

 of 7 litres; this is filled with water which has been boiled and 

 then saturated with carbonic acid, and closed air-tight with a glass 

 plate. Carefully selected subaqueous plants were placed in the 

 water. This physiological actinometer was exposed to the sun's 

 rays, and the quantity of oxygen found was determined. At the 

 same time the action of heat and the brightness of the solar radia- 

 tion was measured. With different heights of the sun the 

 ratio of the oxygen disengaged to the strength of the radiation was 

 almost constant. — Boll, dell Acad, di Catania, Jan. 1891 ; Beiblatter 

 der Physik, vol. xv. p. 418. 



ON WHEATSTONE S DETERMINATION OF THE VELOCITY OF 

 ELECTRICITY. BY PROF. J. STEFAN. 



Kirchhoff, in his paper on the Motion of Electricity in Wires, 

 first showed in 1857 that, under certain conditions, electricity 

 moves in a thin wire according to the laws of wave-motion, and 

 with a velocity which may be put equal to that of light. The 

 agreement between the velocities of electricity and light is only 

 attained when the first travels in a straight wire stretched in the air. 

 Kirchhoff: has restricted his investigation to this case. If the bases 

 of his calculation are applied to other cases, for instance to a wire 

 which is wound in a zigzag, or is coiled in a spiral, it is found that 

 electricity travels in such a wire with far greater velocity. In 

 Wheatstone's well-known experiment a wire was used which was 

 coiled in twenty straight windings, and the velocity of electricity 

 was found to be half as great again as that of light. I think that 

 in the preceding I have given the right explanation of this result. 1 

 have, however, attempted to give this explanation an experimental 

 support, and have employed the method given by Hertz of pro- 

 ducing stationary waves in w 7 ires. I used a circuit like that in 

 Wheatstone's experiment, but on a smaller scale, connected it with 

 a couple of long straight wires, and compared the length of the 

 wave in the circuit with the length of the same wave in the straight 

 wires. The wave in the circuit is considerably longer, and in con- 

 formity with this the velocity of electricity in the circuit is greater 

 than in the straight wires, and, according to my experiments, in a 

 ratio which exceeds that found by Wheatstone. — Wiener Berichte, 

 April 23, 1891. 



