6o 



NATURE 



[November 21, 1895 



scribers will soon send their donations to the Treasurer, Dr. 

 Samuel Gordon, Hume Street, Dublin, The subscription to 

 the memorial is limited to one guinea. It is proposed to place 

 a marble bust of Dr. Ball in the National Museum, the scene of 

 his latest labours. It is further proposed, should there be 

 sufficient funds, to have a portrait of Dr. Ball painted and placed 

 in a position to be hereafter determined. About ;^I20 has so 

 far been subscribed. 



The first meeting of the one hundred and forty-second 

 session of the Society of Arts was held on Wednesday evening, 

 November 20. Previous to Christmas there will be four other 

 ordinary meetings, as follows : November 27, locomotive car- 

 riages for common roads, by Mr. H. H. Cunynghame ; Decem- 

 ber 4, on mural painting, with the aid of metallic oxides and soluble 

 silicates, by Mrs. Anna Lea-Merritt and Prof. W. C. Roberts- 

 Austen, C.B., F.R.S. ;December II, water purification by means 

 of iron, by Mr. F. A. Anderson ; December 18, machines for 

 composing letter-press printing surfaces, by Mr. John Southward. 

 The following papers will be read at meetings after Christmas : 

 Dairy produce, by Mr. George Barham ; the making of a great 

 University for London, by Prof. Silvanus P. Thompson, F.R.S.; 

 some native Irish industries, by Prof. Haddon ; standards of 

 light, by Mr. W. J. Dibden ; ortho-chromatic photography, by 

 Captain W. de W. Abney, C.B , F.R.S. ; the garden in relation 

 to the house, by Mr. F. Inigo Thomas ; English book illustra- 

 tions, 1860-70, by Mr. Joseph Pennell ; Punjab irrigation, 

 ancient and modern, by Sir James Broadwood Lyall, K.C.S.I.; 

 the economic development of Kashmir, by Mr. Walter R. 

 Lawrence. The following courses of Cantor lectures have been 

 arranged : W. Worby Beaumont, on mechanical road carriages ; 

 Dr. J. A. Fleming, F.R.S., on alternate current transformers ; 

 Prof. J. M. Thomson, on the chemistry of metals and alloys 

 employed for building and decorative purposes ; Mr. H. Graham 

 Harris, on refrigeration ; Mr. Henry A. Miers, on precious stones ; 

 Mr. James Swinburne, on applied electro-chemistry. Two 

 lectures, suitable for a juvenile audience, will be deUvered on 

 Wednesday evenings, January i and 8, 1S96, by Prof. John 

 Milne, F.R.S., on earthquakes, earth movements, and 

 'volcanoes. 



A CONFERENCE, presided over by Sir Courtenay Boyle, and 

 largely attended by representatives of municipal corporations, 

 public companies, and others interested in the supply of electri- 

 city, was opened in the Westminster Town Hall yesterday, to 

 consider the revised regulations made by the Board of Trade 

 under the Electric Lighting Acts of 1882 and 1888. We 

 summarise the report in the Times. The regulations were 

 discussed seriatim, and a number of important changes were 

 accepted. With reference to the Board of Trade definition of 

 electrical pressure. Prof. Ayrton, who, with Mr. Compton, 

 represented the Institution of Electrical Engineers, proposed 

 that the expression " pressure " should mean " the difference of 

 electrical potential between any part of any conductor and the 

 earth, or between any two adjacent wires on the three or five- 

 wire system." The Chairman promised that the proposal should 

 receive careful consideration. He added, that he intended to 

 advise the Board of Trade to raise the alternating current limit 

 from 100 volts to a higher figure, say to 220 volts, or thereabouts. 

 With regard to the low-pressure continuous current limit, he 

 thought that it might be raised slightly above 300 volts. 

 Discussion took place upon the regulation that " no high- 

 pressure electric line shall be used for the transmission of more 

 than 200,000 watts, and Mr. Compton suggested that the limit 

 should be 500,000 watts. " The Chairman said he intended 

 to advise the Board of Trade not to adhere to the limit of 200,000 

 watts, but he thought' that of 500,000 watts a little too high. 

 He offered to make an important amendment in the clause 

 NO. 1360. VOL. 53]] 



referring to tests of insulation, the clause in its amended form 

 reading : " Every electric main shall be tested for insulation after 

 having been placed in position, the testing pressure being at 

 least 200 volts, and the undertakers shall duly record the results 

 of the tests of each line or section of a main." With reference 

 to the clause requiring a test of insulation before a high-pressure 

 circuit can be brought into use, the Chairman suggested the 

 introduction of words providing that the test required in the 

 case of electric lines should be twice the pressure to which the 

 lines were to be subjected in use, and in the case of machines or 

 apparatus intended to form part of a high-pressure circuit 50 per 

 cent. more. As to the question of leakages from gas mains, 

 and the accumulation of explosive mixtures in electrical conduits 

 and street boxes, the Chairman said he would be prepared to 

 recommend the Board of Trade to accept a clause based on that 

 suggested by the Institution of Electrical Engineers, that is to 

 say, imposing upon undertakers the obligation to take reason- 

 able means to prevent the influx and accumulation of gas in 

 boxes, and to give notice to the gas companies whenever an 

 accumulation of gas therein was discovered. He accepted that 

 clause on the understanding that there must be some further 

 regulation with regard to the ventilation of street boxes. 



A NOTE on the tinfoil grating as a detector for electric waves, 

 by T. Mizuno, appears in they<7«r«a/ of the College of Science of 

 Tokyo. The author has been repeating and extending Aschkinass' 

 most interesting experiments on this subject. The gratings em- 

 ployed are formed by coating a flat wooden block with tinfoil, 

 and then cutting on it a number of fine parallel sHts with a 

 sharp knife. Two gratings have been used, one having a resist- 

 ance of 130 ohms, and the other of 232 ohms. The wave-length 

 of the electric radiation employed was about 60 cm. On ex- 

 posure of these gratings to the electric radiation, the resistance 

 fell in some cases as much as 1 1 ohms and 42 ohms respectively. 

 Gentle tapping was sufficient to cause the resistance to increase 

 to almost its former value. The experiments indicate that 

 the angle which the plane of polarisation of the radiation 

 makes with the strips of the grating influences the results 

 to a certain extent, a greater decrease of resistance taking 

 place when the strips are perpendicu'ar to the plane in 

 which the primary oscillations take place. The author has 

 made some experiments with a view of determining whether 

 the change in resistance is due to a molecular change 

 in the tinfoil, or whether the change is a mechanical one. 

 He has constructed gratings in which the spaces between the 

 strips were much larger than in the above gratings. With this 

 grating, however, no indication of a decrease of resistance under 

 the action of electric radiation was observable. Gratings formed 

 of fine german-silver wire and fine iron wire, also, showed no 

 effect. The author concludes that the change is a mechanical 

 one, and suggests that it may be due to small jagged points on 

 the neighbouring strips coming into contact under the influence 

 of the electric waves. 



The competition for mechanical carriages, which was arranged 

 by the Tunes-Herald of Chicago to take place on November i , 

 has been postponed until the 28th inst., at the request of a num- 

 ber of the competitors who had entered for the competition, but 

 were not prepared. According to thtjournaloi the Society of Arts, 

 the TJtnes-IIeraldi\iQxe\i^n offered a prize of ;^ioo, to be divided 

 amongst those competitors who went over the course arranged 

 for the race. This course extends over the line of boulevards 

 which surround Chicago to a place named Waukegan on the lake 

 shore, thirty miles to the north of the city. Several vehicles 

 started, but only one completed the course — the carriage entered 

 by A. Mueller, of Decatur, Illinois. The vehicle carries four 

 persons, and is driven by a gasoline motor. The total distance 

 covered was ninety-two miles, and the time taken 8 hours 44 

 minutes. 



