i6o 



SCIENCE. 



[Vol. XIII. No. 317 



dence that many similar customs must have originated independently 

 in regions far apart. Among many other phenomena, the author 

 traces the occurrence of masks among various peoples, and shows 

 that they occur all over the world, in America as well as in Aus- 

 tralia and all parts of the Old World. It seems that the games in 

 which our children delight are well-nigh universal. The children 

 of the ancient Egyptians played tag ; they had balls and dolls. 

 Bodies of dolls were made of wood, and might be mistaken for 

 modern fabrics. Undoubtedly they were dressed by the Egyptian 

 girls, as our girls nowadays enjoy dressing their dolls. There were 

 even movable ones, the hands and feet of which could be moved 

 by means of strings. Others, made of painted wood, were very 

 imperfect in form, and had strings of beads instead of hair. In the 

 museum of Leyden there is an ancient toy that looks as though it 

 had been bought at a Christmas fair. There were figures of 

 animals with movable mouths, and balls of leather. Among 

 Greek and Roman antiquities, dolls made of wood or clay, and 

 others of wax and ivory, are found. Dolls' houses with lead furni- 

 ture ; the saving- box with a slit on top ; toy cows, horses, and 

 hogs, — were known to the children of ancient Rome, as they are to 

 our own. From this evidence it might be supposed that our dolls 

 are " descendants " of the ancient dolls ; but it must be remembered 

 that there is hardly any people that does not have them. Their 

 use is so general, and so natural to the child, that even the laws of 

 Mohammedanism are disregarded by the childish desire. The Koran 

 forbids representations of human beings, and still the Moham- 

 medan child plays with its doll. The women of Bagdad believe 

 that a doll may eventually come to life, and harm their children, 

 and therefore prevent their use. The girls, however, play with 

 cushions and pieces of wood instead, which they nurse and dress. 

 In Siberia and arctic America ivory dolls, clothed in furs, of 

 beautiful workmanship, are found ; in Peruvian graves, dressed 

 dolls of clay are found ; and in Africa the girls play with wooden 

 or clay figures. In this way Andree traces numerous ethnological 

 phenomena in their distribution among various peoples, and shows 

 that the human mind everywhere develops on the same lines, and 

 that a migration of inventions must be supposed only in such cases 

 where its existence can be proved by historical facts. 



ELECTRICAL NEWS. 



Ether, Electricity, and Ponderable Matter, 



Sir Willi AM Thomson's presidential address before the English 

 Institute of Electrical Engineers was looked forward to with some 

 eagerness by electricians. The title given above is fascinating, and 

 promises solutions of questions which have been asked for so many 

 years, and whose answer had seemed so hopeless. We think that 

 the address is disappointing. It tells us little that we did not know, 

 and, although suggestive, it hardly points out how to follow the sug- 

 gestions. 



After a few introductory remarks, Sir William dwelt briefly on the 

 necessity of an electrician being also an engineer. He would give 

 a youth desiring to take up the study of electrical engineering a 

 good deal of chemistry, of mathematics, and of dynamics. " I am 

 perfectly sure, that, if the youth is qualified in other departments, 

 the mere addition of electricity to the education of a corrfpetent 

 engineer will not take such a long time as might be imagined, and 

 that the merely educational part of the work will not be protracted 

 unduly by adding electricity to the branches learnt in general en- 

 gineering." 



Passing to the main subject of his address. Sir William spoke of 

 the demand that was every year growing in intensity, for something 

 like a mechanical explanation of electrical phenomena : " to know 

 something of the internal relations connected with the wonderful 

 manifestations of force and energy which are put before us in the 

 action of the magnet, in the working even of a common electrical 

 machine, and in electro-magnetic phenomena." The question of 

 the transmission of messages through cables was then taken up at 

 some length, and the history of the theory on which the first At- 

 lantic cable was constructed was given. Sir William then spoke of 

 the two effects which must be considered when an electrical wave 

 is transmitted, — that due to static induction, and that due to mag- 

 netic induction. In the first solution of the problem, only the 



statical effects were considered, since the propagation was so slow 

 that they were large compared with the magnetic effects ; but Mr. 

 Heaviside has lately shown that the magnetic induction is really an 

 advantage in signalling or in transmitting speech by telephones, 

 since it makes the dying-out effects much more uniform. If only 

 static induction were considered, the waves of short period would 

 die out more quickly than those of greater length. The magnetic 

 induction helps to make this difference less, and is therefore bene- 

 ficial. 



Taking up the subject of alternating electric currents in wires, 

 the speaker gave some figures on the increase in the resistance of 

 a wire carrying alternating currents as compared with the resistance 

 of the same wire for continuous currents. It has become well 

 known in the last few years that the distribution of a varying cur- 

 rent in a wire is not uniform, but the density is greatest near the 

 outside. This has the effect of increasing the resistance : for in- 

 stance, taking a period of 80 reversals per second, the increase in 

 resistance of a wire i centimetre in diameter is not so much as .01 

 per cent; for a diameter of 1.5 centimetres the increase is 2.5 per 

 cent ; for 2 centimetres it is 8 per cent ; for 4 centimetres, 68 per 

 cent. For periods of twice the frequency we must multiply by Vo. 

 The inward penetration of the current into the wire may be com- 

 pared to the motion of water in a long tube, when the tube is moved 

 backward and forward in the direction of the axis. To represent 

 the case of alternating currents in parallel wires. Sir William would 

 replace the wires by densities of fluid in direct proportion to the 

 electric conductivities, the space around being a fluid without mass, 

 the cylinders of dense matter rotating periodically in opposite direc- 

 tions. To represent the electro-static effect in such a case, " imagine 

 an interface between the two fluids, and give it such stiffness against 

 change of shape as is required to cause it to fulfil the conditions 

 which electro-static knowledge, and our knowledge of the laws o£ 

 electric and electro-magnetic influence, dictate to us." 



Sir William then went on to say that he believed that an electric 

 current actually caused a rotation of the ether, and considered the 

 case of a copper core surrounded by a helix. Induced currents 

 were set up in the copper, and the only action conceivable in the 

 space between the coil and the core was a rotation. This might be 

 either a continuous rotation, or a rotation through an angle propor- 

 tional to the strength of the current. In iron, however, something 

 quite different must take place. If the fluid whose rotation caused 

 the observed effects moved around continuously, there would be no 

 shearing. If, on the other hand, there were only a drag upon the 

 ether through a certain angle, then there must be a force resisting 

 steady rotation ; that is to say, there would have to be an arrange- 

 ment of such character that a constant torque would produce a 

 constant instead of an accelerated rotation. It would appear that 

 such an effect could only be produced by an inherent rotation of the 

 molecules. To represent a medium of this kind. Sir William imag- 

 ines a space divided up into a number of small squares, with their 

 sides fixed together by rubber bands. In each a gyrostat in the 

 form of a rotating molecule is placed. Such a medium, without the 

 gyrostats, would repixsent a perfect fluid ; but, with the gyrostats 

 in place, turning could only take place by stretching the elastic 

 bands, which would require a constant force. On this hypothesis, 

 we must suppose that the ether is less rigid in iron than in other 

 metals, and has the same rigidity for all non-magnetic substances. 

 But no model that can be imagined can represent the electro-static 

 as well as the magnetic effects. In concluding. Sir William pointed 

 out that even the very imperfect attempts at a mechanical explana- 

 tion of electrical phenomena which he had indicated would only 

 apply to a very small part of the subject ; and the tremendous 

 difficulties in the way of a complete mechanical explanation prevented 

 him from hoping to see the question solved in his own lifetime, 

 though he felt confident that a solution would be found, and that 

 what appeared so insuperable a mystery to us would be no mystery 

 at all to future generations. 



An Electric Date Stamp. — According to Engineering, the 

 Electric Date and Time Stamp Company are introducing a new 

 stamp, which at one operation marks on any document the minute, 

 hour, day, month, and year, as well as the usual address and busi- 

 ness of the proprietor. Unlike many automatic appliances which 

 are dubbed electrical merely for the purpose of imposing on un- 



