418 



SCIENCE. 



[N. S. Vol. IX. No. 220. 



taken, however, and the comet was rediscovered 

 by Horace P. Tuttle at the Harvard College 

 Observatory, January 4, 1858. 



Johannes Rahts, of Kouigsberg, made the 

 most complete discussion of the orbit, combin- 

 ing the observations of 1858 and 1871-2, having 

 regard also to the perturbations. His value of 

 the period is 13.7 yrs. The comet was next 

 seen in 1885, and was expected during the pres- 

 ent year. An ephemeris was accordingly dis- 

 tributed from Kiel, and it was probably by 

 means of this that a faint comet, supposed to 

 be Tuttle's, was discovered March 5th, by Dr. 

 Wolf, as already announced. This ephemeris, 

 as corrected by Dr. Wolf's observation, is 

 given below. 



Harvaed College Observatory, 

 March 8, 1899. 



A NEW STAR IN SAGITTARIUS. 



From an examination of the Draper Memorial 

 photographs, Mrs. Fleming has discovered a 

 new star in the constellation Sagittarius. Its 

 position for 1900 is: R. A. = 18''56.2°', Dec. = 

 — 13° 18'. It was too faint to be photographed 

 on eighty plates taken between October 18, 

 1888, and October 27, 1897, although stars as 

 faint as the fifteenth magnitude appear on some 

 of them. It appears on eight photographs 

 taken while it was bright. On March 8, 1898, 

 it was of the fifth magnitude, and on April 29, 

 1898, of the eighth magnitude. A plate taken 

 this morning, March 9, 1899, shows that the 

 star is still visible, and is of the tenth magni- 

 tude. Two photographs show that its spectrum 

 resembles those of other new stars. Fourteen 

 bright lines are shown, six of them due to hy- 

 drogen. The entire number of new stars dis- 

 covered since 1885 is six, of which five have 

 been found by Mrs. Fleming. 



B. C. Pickering. 



Harvard College Observatory, 

 March 9, 1899. 



NOTES OX PHYSICS. 

 ELECTRIC WIRE WAVES. 



The theory of electric waves along wires has 

 been worked out very completely by J. J. 

 Thomson for the case of a wire surrounded by 

 a cylindrical conducting shell. A further de- 

 velopment of the theory, together with some 

 interesting numerical results is given by A. 

 Sommerfeld in Wiedemann's Annalen, 1899, No. 

 2. The author gives a rigorous solution of 

 Maxwell's equations for electric waves trans- 

 mitted along a straight wire of great length. 

 This rigorous solution leads to an equation in 

 Bessel's functions, the roots of which give the 

 velocity of transmission and the damping co- 

 efficients. The author gives approximate solu- 

 tions of this equation for wires of great conduc- 

 tivity, diameter of wire being rather small com- 

 pared to the wavelength, and for wires of 

 medium conductivity, diameter of wire being 

 very small compared to wave-length. In these 

 two cases the equation in Bessel's functions re- 

 duces to a logarithmic form for which the roots 

 may be found without serious difiiculty. 



The author gives the following calculated re- 

 sults : Electric waves of 30 cm. wave-length 

 travel along a copper wire of 4 mm. diameter 

 at a velocity which is less than the velocity of 

 light by one part in 30,000, and the amplitude 

 falls to :J- of its initial value at a distance of 1.5 

 kilometers. 



Electric waves of 100 cm. normal wave-length 

 (period 33-10-'° second) travel at about three- 

 quarters of the velocity of light along a platinum 

 wire .004 mm. diameter, and their amplitude 

 falls to 7^ of its initial value at a distance of 

 only 17 cm. 



The author also gives a diagram of the lines 

 of electric force inside and outside of the wire, 

 the lines of magnetic force being circles around 

 the wire. W. S. F. 



A NEW INDICATOR FOE ELECTRIC WAVES. 



A GALVANOMETER of medium sensitiveness is 

 connected to a battery, a strip of silvered glass 

 is included in the circuit and the coating of sil- 

 ver is scratched across so asi;o break the circuit. 

 The strip is placed in moist air and the galva- 

 nometer shows a deflection. When the strip is 



