Chemistry and Physics. 77 



between the anode and an exploring wire near it, was a minimum 

 when tke exploring wire was at a short distance from the anode, 

 so that the apparent electric intensity near the anode was nega- 

 tive. These results are confirmed by Harold A. Wilson, who 

 measured the differences of potential between two exploring 

 wires kept at a fixed distance apart in the discharge, which could 

 be brought into any desired portion of the discharge by moving 

 the electrodes between which the discharge took place. This dis- 

 charge was produced by a storage battery of 600 cells. The 

 gases employed were air, nitrogen, and hydrogen. The positive 

 drop close to the anode was very apparent from the experiments. 

 Very close to the positive electrode there is apparently a very 

 intense ionization. In the negative glow and Faraday dark space 

 there is also ionization in excess. In every kind of electric dis- 

 charge ionization appears to occur on the metallic electrode when 

 it is red hot and most easily there. The negative ions formed at 

 the surface of the cathode constitute the cathode rays, and pro- 

 duce the ionization which the intensity curves show occurs in the 

 negative glow. — Phil. Mag., June, 1900, pp. 505-516. j. t. 



10. Mechanical possibilities of flight. — Lord Rayleigh in the 

 Wilde lecture published in the Manchester Memoirs 1899, No. 5, 

 discusses this proposition and shows that in order for a man to 

 support himself by a vertical screw by working at the power an 

 average man can maintain for eight hours a day, he would require 

 a screw ninety meters in diameter; and in this estimate no account 

 is taken of the weight of the mechanism or of frictional losses. — 

 Nature, May 31, 1900. j. t. 



11. Magnetic Screening. — The great extension of electric cir- 

 cuits for lighting and for power makes it impossible in most cases 

 to use the ordinary form of mirror galvanometer. H. Du Bois 

 and A. P. Wills discuss the subject of the protection of galva- 

 nometers from outside changes in the magnetic field produced by 

 the commercial employments of strong currents. The cases of 

 iron cylindrical shells and of spherical shells is treated and the 

 results are used by H. Du Bois and H. Rubens in the construction 

 of a protected or armored galvanometer (Panzergalvanometer). 

 Cast-steel cylinders having a radius ratio of air space 1*5 to 1*6 

 and spherical cast-steel shells 1*3 to 1*4 give in general this order 

 of protection : one shell, 10; two shells, 100; three shells, 1000. — 

 Ann. cler Physik, pp. 78-95. j. t. 



12. The Sun's Corona.— Mathias Cantor in the Ann. der Physik 

 for March, 1900, believes from his experiments that a rarefied gas 

 through which an electrified discharge is passing shows no per- 

 ceptible absorption corresponding to its emission spectrum, and 

 Professor Fitzgerald in Nature, May 3, 1900, remarks that this fact 

 confirms the suggestion that the sun's corona is an electrical dis- 

 charge around the sun since the bright spectrum line of the corona 

 is not represented by a dark line in the solar spectrum. E. 

 Pringsheim criticises severely the results of Cantor and believes 

 that he has not taken suitable precautions in his experiments. 



