24 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



contributes to the formation of the tails of comets. The 

 actual existence of this force is established by the accurate 

 observations that have been made. He examines successive- 

 ly the various theories that have been put forth the elec- 

 trical theory as proposed by Zollner, the molecular theory 

 of Zenker, and the theory of Faye that repulsion is exerted 

 by all incandescent surfaces, and that thereby the gaseous 

 matters attending the comets are repelled from the surface 

 of the solid nucleus. The latter does not seem to Schiaparelli 

 to afford any material explanation of the phenomena. The 

 electric theory was first suggested by Olbers, but has been 

 in general terms objected to by Herschel, Lamont, etc. Zoll- 

 ner's views have been elaborated more minutely, and he has 

 endeavored to show that the free electricity existing upon 

 the surface of the earth is sufficient to produce an effect sim- 

 ilar to that found in comets ; but his conclusions are in too 

 many respects at variance with actual observations to allow 

 the author to consider them as affording a reasonable expla- 

 nation as to the nature of comets. Zenker's views are rejected 

 by him for the reason that the evaporation of fluids from the 

 surface of the nucleus should give rise to several phenomena 

 not seen in comets, while, on the other hand, it does not ex- 

 plain the multiple tails which have frequently been observed. 

 In conclusion, Schiaparelli thinks that we are forced to be- 

 lieve that the repulsive force acting upon comets is a force 

 exterior to the comet itself, and since this force evidently 

 operates in the direction of the radius drawn from the comet 

 to the sun, therefore we must regard it as having for its 

 origin the sun or some medium surrounding the sun, and he 

 adds that this is about all w T e at present know upon the 

 subject. 3 B, XXXV., 263. 



avinnecke's comet. 



The comet known as Winnecke's comet is a very faint 

 telescopic comet, whose recent appearance was observable 

 by only a few of the largest telescopes in the world. It was 

 first observed in 1819, but attracted no notice until in 1858 

 it was again observed by Winnecke. From the observations 

 made at that time, Winnecke showed that it accomplished 

 its revolution in its orbit in about 2400 days, and that it 

 w r as identical with the comet of 1819, having made seven 



