December 16, 1898.] 



SCIENCE. 



859 



during that period by refereace to the silver 

 voltameter. 



The result of this preliminary investiga- 

 tion showed that the silver value of the true 

 ampere was so nearly equal to the reputed 

 value, viz., 1.118 milligram per second, as 

 to require the use of an apparatus still 

 more perfectlj^ constructed, and, therefore, 

 of a much more expensive character to en- 

 able the error, if any, iu this value to be 

 ascertained with accuracy. 



We, therefore, started on the design of the 

 instrument, of which we now submit the 

 working drawings, and for the future con- 

 struction of which we would ask for a grant 

 of £300, including the unexpended grant of 

 £75 voted last year.* And we anticipate 

 that this new piece of apparatus may prove 

 worthy of constituting a national Ampere 

 Balance, the counterpoise weight for which 

 will be determined purely by calculation 

 based on the dimensions of the instrument, 

 the number of convolutions of wire in the 

 three coils, and the value of the accelera- 

 tion of gravity at the place where the in- 

 strument may be permanently set up. In 

 this particular it will differ entirely from the 

 ' Board of Trade Ampere Standard Verified 

 1794,' which has had its counterpoise weight 

 adjusted so that the beam is horizontal 

 when a current passes through the instru- 

 ment, which will deposit exactly 1.118 milli- 

 gram of silver per second under specified 

 conditions. In fact, the proposed Ampere 

 Balance and the existing Ampere Standard 

 will differ exactly in the same way as do a 

 Lorenz apparatus and the ' Board of Trade 

 Ohm Standard Verified, 1894.' 



We have to express our thanks to Mr. 

 Mather for taking charge of the construc- 

 tion and use of the preliminary apparatus, 

 for checking all the calculations in connec- 

 tion with the determination of the electro- 

 ■chemical equivalent of silver that was 

 Inade with it, as well as for superintending 

 • * This grant of £300 has since been made. 



the making of the working drawings of the 

 new Ampere Balance. 



We have also to thank Messrs. W. H. 

 Derriman and W. N. Wilson, two of the 

 students of the City and Guilds Central 

 Technical College for their cordial assist- 

 ance in carrying out the work. 



W. E. Ayrton, 

 J. ViEiAMu Jones. 



NOTES ON PHYSICS. 

 ELECTRICAL VIBRATIONS. 



In Wied. Ann., 1898, No. 11, M. Abra- 

 ham gives a solution for the electrical oscil- 

 lation of an ellipsoidal conductor (ellipsoid 

 of revolution) and an approximate solution 

 for the electrical oscillation of a straight 

 rod. Perhaps the most interesting feature 

 of the paper is the detailed analysis of the 

 reflection of an electrical wire-wave from 

 the free end of the wire. 



The wave-length of the Hertz waves sent 

 out from a vibrating rod are shown to be 

 the double length of the rod, a fact which 

 has been known experimentally for some 

 time, and the overtones are harmonic. 



It may be remembered that Tesla, a few 

 years ago, suggested (and perhaps tried I) 

 the use of electrical oscillations of the earth 

 as a means of telegraphy. The solution of 

 the problem of the electrical oscillation of 

 a sphere was well known (?) at the time, 

 and this solution indicates that to maintain 

 the electrical oscillations of a sphere only a 

 few inches in diameter would require mil- 

 lions of horse-poiver, and, of course, to stir 

 up the earth electrically would require an 

 enormously greater amount. Tesla did not 

 succeed. 



MANOMETEIC FLAMES. 



Professors Nichols and Merritt publish, 

 in the August number of the Physical Review, 

 an interesting series of manometric-flame 

 photographs. The reproductions are as 

 good, perhaps, as is possible, but the original 



