A. MATHEMATICS AND ASTRONOMY. 35 



tliat he can say with considerable certainty that there is no 

 satellite within two minutes of the planet Uranus, outside 

 of Oberon. Appendix I. to theWasJdngton Observations foi' 

 1873/ 



OBSERVATIONS OX THE ZODIACAL LIGHT. 



In the volume of observations on the zodiacal light, pub- 

 lished by Heis, he gives a slight historical sketch of the ob- 

 servations of that phenomenon, from which it appears thatliis 

 own observations were begun by him at Aix-la-Chapelle in 

 1847, and continued by him there until 1852, since which 

 time they have been pursued at his residence at Miinster. 

 In 1864 Weber, at Peckeloh, began to assist him. In 1843 to 

 1845 Schmidt, of Athens, and in 1853 to 1856 Rev. George 

 Jones, of the United States, observed the zodiacal light. A 

 large number of other observers are mentioned by him, from 

 w^hose observations he has drawn liberally in compiling such 

 notes as he has thought appropriate. The total number of 

 zodiacal-light observations given by him is thirty-four, most 

 of them observed very fully by at least one person, and oft- 

 entimes by two. Some of the records are much fuller than 

 others, but in all sufficient is given to find the exact place of 

 the light, its limits, its apex, and axis. Zodiacal Liglit Ob- 

 servations by Edioard Heis, Mimster, 1875. 



THE COMET IH., 1862. 



This comet threw out in the neighborhood of the sun a 

 second and supplementary tail, which was carefully observed 

 by Schiaparelli at Milan {Pub. del It. Oss., etc., ii., p. 21). 

 Bredichin, of Moscow, has discussed these observations on 

 the supposition that this tail was in the plane of the orbit, 

 and he computes for each observation the angle of the tail 

 and the radius vector, the length of the tail, etc. The values 

 of these quantities show that the tail preceded the radius 

 vector in its motion through space, and that the force which 

 was necessary to the formation of the tail Avas in terms of 

 the force of gravitation (=1) 1.013. Supposing this force 

 to be 1.000, Bredichin computes the velocity of the luminous 

 jets for this comet, and finds it to be equal to 0.02 ; for 

 Ilalley's comet Bessel found this velocity 0.04 ; for the comet 

 of 1858 this was 0.14; for the comet of 1811 it Avas 0.17. 



