M. 



►9, 1890] 



NATURE 



107 



which its ardent inventor hoped would work well at 120 

 words, now works equally well at 600 words a minute. 



The telephone, owing to mismanagement and the 

 operation ot our Patent Laws, has not received much de- 

 velopment in England yet ; but with the expiry of the 

 patents at the end of this year it is hoped that every 

 post-office will become an exchange, and the business of 

 telephony will flourish as well in England as it has in 

 Sweden and Norway and some of the smaller States in 

 Europe. Competition and free trade will certainly tend 

 to bring this marvellous and beautiful apparatus within 

 the sphere of every domestic circle. 



It is marvellous how science is rapidly becoming a 

 household god. The electric light, bells, and telephones 

 must prompt all to some knowledge of electricity. Ventila- 

 tion, sanitation, pure water, warming apparatus, lead to a 

 knowledge of other scientific principles. The laws of 

 Nature are rapidly but surely becoming as familiar in 

 our mouths as household words. 



PEND UL UM ELEC TROME TER. 



T N order to obtain an inexpensive apparatus by which 

 ■*■ the nature of electrostatic measurements could be 

 clearly presented to students, and the measurements 

 carried out before a class with ease and despatch in abso- 



lute units, Prof. Mayer, of the Stevens Institute of Techno- 

 logy, of New Jersey, has arranged the apparatus shown 

 in the accompanying figure. 



It consists of a gilt pith ball of i cm. radius, made of 

 pieces of pith cemented together, and suspended at a 

 distance of 364 cm. from the ceiling by a very fine silk 

 fibre passed through a small staple driven into the ball. 

 The ends of the fibres are attached to the ceiling at a 

 distance of 52 cm. apart, and arranged so that the sus- 

 pended ball can be raised or lowered, until it is at the 

 same height as a brass ball, also of i cm. radius, sup- 

 ported on a glass rod, coated while hot with paraffin wax. 

 A force of i dyne acting on the suspended ball deflects 

 it through I3'3 mm., and, as 2° deflection was the maxi- 

 mum employed, the scale was inclined to the horizontal 

 so as to coincide with the chord of an angle of 2°. 



If a charge be given to the two small balls when in 

 contact, and when therefore it will divide equally between 

 them, the charge on either in absolute electrostatic units 

 equals 



D /~^" 



where d'ls the deflection in centimetres of the pendulum 

 from the vertical, and D the distance in centimetres 

 between the centres of the two balls. 



To test the sensitiveness of the apparatus, the ball on 

 the stand was placed at various distances from the sus- 

 pended one, and the force between them observed. The 

 law of the inverse squares was found to be verified with 

 an error of less than i per cent, when D was over s\ cm. 

 Next the gradual diminution of the deflection when the 

 brass ball on the stand was in a fixed position was used 

 to measure the rate of loss of charge, and it was found 

 that the measured leakage to earth was proportional to 

 the measured charges with a considerable degree of 

 accuracy in several experiments, and with a maximum 

 error of 20 per cent, in the most discordant experiments. 

 Then the pendulum electrometer was used to measure 

 the electric distribution over the surface of a cylinder, a j 

 proof plane being employed to convey the charge from ' 

 different parts of the surface of the cylinder to the I 

 pendulum electrometer, and results were obtained closely \ 

 agreeing with those obtained by Coulomb. Lastly, the 

 potential of the large sphere was experimentally deter- I 

 mined in absolute electrostatic units for different charges I 

 given to it. ' 



NO. 1074, VOL. 42] 



NOTES. 



We are glad to learn that the President of the Frencli Republic 

 has conferred on Prof. Sylvester and Prof. Cayley the " Decora- 

 tion d'Officier de la Legion d'Honneur." This honour has been 

 granted in consequence of a request addressed to the French 

 Minister of Foreign Affairs by the President and other members 

 of the Academy of Sciences. 



Lord Ravleigh has been elected a corresponding member 

 of the Imperial Academy of Sciences in Vienna. 



The French Association for the Advancement of Science will 

 hold its nineteenth meeting at Limoges from August 7 to 14. 

 Various English men of science have been invited by the Bureau 

 of the Association to attend the meeting, and they are asked to 

 let their decision be known before July i. Those of them who 

 accept the invitation will be the guests of the Municipality of 

 Limoges. 



The Queen has been pleased to approve of the grant of Civil 

 List pensions to Miss Charlotte, Ruth, Mai^aret, and Rose, 



