3° 



SCIENCE. 



[Vol. XII. No. 285 



When it comes to supplying an entire city with hght, and the 

 question of the relative cost of the various systems is considered, it 

 vifill probably be found that the most economical will be not any 

 one of the systems, but all of them, — two or three stations in the 

 city proper for the direct and storage systems, the latter for locali- 

 ties distant from the central stations. For the suburbs the alternat- 

 ing system could be used, the stations supplying the alternating 

 currents also supplying arc lights. 



It should be noticed that in the discussion in England before the 

 Society of Telegraph Engineers and Electricians, Mr. Kapp, who 

 championed the alternating-current side of the question, admitted 

 that a system of distribution by storage-batteries was the ideal 

 system, but he said that he knew of no reliable storage-batteries. 

 Mr. Crompton's system is not a complete storage system : as has 

 been pointed out, he uses the secondary batteries more for convert- 

 ers than for their storage properties. In a complete storage sys- 

 tem the batteries should be so arranged that the full capacity of the 

 station is utilized, so that the engines and dynamos are giving 

 their maximum output the whole twenty-four hours. To do this with 

 safety, there should be two sets of cells, one being charged while 

 the other is discharging. There can be no question that storage- 

 batteries have been greatly improved in the last few years, there is 

 no question about the possibility of future improvement : so we 

 may look'for developments in this direction. 



If the discussions have shown anv thing, they have shown that 

 the direct system is the best for crowded centres, the alternating 

 for scattered towns and suburbs, while Mr. Crompton's storage 

 system could be used to at least double the area of economical dis- 

 tribution from a direct-current station. 



Electrification of Metal Plates by Irradiation with 

 Electric Light. — The influence of light on electric phenomena, 

 which has attracted so much attention in the last year, is being 

 made the subject of numerous researches. Mr. Hallwachs de- 

 scribes some interesting experiments that he has lately carried out. 

 A metal plate was suspended inside of an iron cylinder whose axis 

 was horizontal. The plate was five centimetres in diameter. The 

 cylinder was fifty centimetres long by thirty-seven centimetres in 

 diameter. The surface of the plate was coated with rust except in 

 one spot, where it was brightly polished. It was first connected 

 with the earth. The wire by which it was suspended passed 

 through, but insulated from, an earth-connected brass tube, to an 

 electrometer. In one end of the iron cylinder was a circular aper- 

 ture eight centimetres in diameter, covered with wire gauze to pre- 

 vent any inductive influence of the electric lamp used on the plate. 

 The cylinder was electro-negative to the case, so that any trans- 

 port of electricity by radiation — a phenomenon described by M. 

 Righi — would have charged the plate negatively. If, now, a plate 

 of mica was placed in the aperture in the cylinder, and the plate 

 illuminated by an electric light, there was no indication on the 

 electrometer. If, however, the plate of mica was replaced by a 

 much thicker plate of selenite, the electrometer gave a gradually 

 increasing deflection, indicating positive electricity. This at once 

 ceased when the selenite was replaced by mica. The rise of po- 

 tential cannot, therefore, be due to an inductive action, nor can it 

 be referred to the action of heat.' The metals which were used for 

 the experiments just described were zinc, brass, and aluminium. 

 In all three, positive electricity occurred on irradiation with brightly 

 polished surfaces. Old surfaces no longer showed the phenome- 

 non. The radiation itself lowers the potential to which the plates 

 can be electrified ; so that with any succeeding experiment made 

 with the same surface the potential obtained is lower, while the 

 rise to it takes place more rapidly. The maximum potential with 

 zinc amounted to over a volt, with brass to about one volt, and 

 with aluminium to five-tenths of a volt. 



EleCTRIC^LiGHTING in Mines. — For some years past efforts 

 have been made to introduce electric lights in mines, and rewards 

 have been offered in England for the invention of some safe, re- 

 liable, and economical system of lighting. The difficulties to be 

 contended with are these : For permanent lights there is trouble 

 in insulating the leads in such a way as to prevent possibility of 

 breaks or grounds, the demand on the insulation being particularly 

 trying, while there is danger that the breaking of the lamps 



will explode any inflammable gases around them. For miners'" 

 lights, the greatest trouble is to get a portable battery that can be 

 easily carried, and which is cheap and simple. In this country no 

 advance has been made in the application of electricity to mine- 

 lighting ; but in England much attention has been directed to it, 

 and electric miners' lamps are being extensively introduced. In 

 the National Colliery, Rhondda Valley, no less than eight hundred 

 such lamps are used, while they are being introduced into other 

 mines controlled by the same company. These are on the Swan 

 system. At Cannock Chase the Pitkin system is employed ; at 

 Aldwarke, the Sun system. With the excellent primary batteries- 

 that have been lately brought out, and with the improvements that 

 have been introduced in miners' lamps, it is probable that they will 

 soon be largely used in mining-work. 



BOOK-REVIEWS. 



Proceedings of the Society for Psychical Research. Part XIL 

 June, 1 888. London. Soc. Psych. Research. 



This number of the Proceedings deals almost exclusively with a 

 class of facts towards which it is becoming more and more dif- 

 ficult for the man of science to assume a fitting attitude. The men 

 who vouch for the correctness of the facts are in part drawn from> 

 their confreres, eminent in other branches of science. They are ap- 

 parently on their guard against some, at least, of the many and 

 various forms of deception. They, with some exceptions, set forth 

 their results with much candor, and without conscious bias. And 

 yet one reads their writings with the conviction, that grows as one 

 reads, that all this is premature, that these men do not give evi- 

 dence of that same comprehensiveness and scientific reserve which 

 they would exhibit in case of a problem touching upon their own 

 specialty. One feels the absence of a sound psychologic insight,, 

 such as comes only from years of special training, and the experi- 

 ence of a life dominated by a powerful interest for this kind of 

 phenomena. One longs for the counterpart of such a man as 

 Robert-Houdin, training every sense to its maximum of sensitive- 

 ness, and every muscle to the utmost expertness, in order to be a 

 master in the art of deception. In the goings-on of his daily life he 

 is constantly on the alert for some chance combination of events 

 that suggest a new mode of misleading the spectators of his con- 

 juring. Again, the length of the articles ; the large proportion of 

 theorizing ; the lack of constant reference to the results of others, 

 especially of those not in harmony with their own views, — all this, 

 not to mention occasional serious faults in logic and sad deficien- 

 cies in the stringency of the observations, will far postpone the 

 day when these Proceedings will be found on the shelves of a 

 strictly scientific library. 



The English Society for Psychical Research, it need scarcely be 

 said, has definitely accepted the hypothesis of telepathy, — of the 

 action of mind upon mind apart from the recognized channels of 

 sense. They accept this not merely as the only satisfactory prin- 

 ciple by which their facts can be accounted for, but they are ready 

 to use the theory as a means of explaining other groups of facts. 

 All of the four main contributions to the present number deal with 

 facts of telepathy, and largely with the relation of this power to- 

 hypnotism. M. Charles Richet takes up one hundred and fifty 

 pages with an account of a very elaborate and extended series of 

 observations of such transferrence. This paper is to be ranked as 

 among the most serious evidence that has yet been presented, and 

 will be noticed in a future number of Science. Messrs. Schmoll 

 and Mabire describe very similar experiments, but conducted with 

 far less caution and insight. Failures are overlooked as unimpor- 

 tant. Just at the point where one desires most accurate informa- 

 tion, the account is vague. The percipient is allowed too many 

 trials, is too clearly informed of his success. The series in which 

 the conditions were most convincing " produced only failures." 

 The repeated statement of the percipient after seeing the object he 

 was to think of, that at first this had come to his mind but was re- 

 jected, is recorded with great naivete. Such illusory instructions 

 as that the agents must entertain no " secret hope of failure " are 

 seriously recorded. All this renders these observations of little 

 weight. 



