28 KANSAS CITY REVIEW OF SCIENCE. 



of the sun, and if the nuclei of comets are glowing masses, the question is more 

 pressing owing to the small quantity of matter which they contain. Moreover, 

 the luminous streamers from the sun alluded to above would seem to indicate the 

 presence of that agency which produces the tails of comets, and also would seem 

 to explain some phenomena exhibited in the heads of comets. 



There are are other analogies between the sun and comets which could be 

 cited, but I think enough has been said to show it probable that comets are simi- 

 lar to the sun in physical composition. We will now give back to the comet its 

 tail and briefly consider the cause of that wonderful phenomenon. 



There seems to be no room for doubt that the agency which generates the 

 tail of a comet must be sought in the sun, and that it consists of a repulsive force 

 exerted by that luminary upon the nebulous envelope of the comet. This is sup- 

 ported in some cases by calculation. The tail of Donati's Comet of 1858 having 

 been found to be nearly the shape which it would have taken under the operation 

 of a repulsive force exerted by the sun. 



Now, as this repulsion begins to act, assuming the nebulous matter of the 

 comet spherical to begin with, it would naturally cause this substance to bank up 

 between the nucleus and the sun, thus increasing its temperature and density 

 and making it more luminous than any portion of the comet except the nucleus : 

 thus forming what is called the nebulous envelopes. This repulsive force may 

 be electrical, as has often been supposed, or it may be that same force which pro- 

 jects the luminous streamers from the surface of the sun, but whatever it is, it is 

 impossible that it alone could produce all the phenomena which are presented in 

 the tails of comets; because, generally, while the tail of a comet is single — it is 

 turned directly from the sun and slightly curved toward that region of space 

 which the comet has just left, and while its magnitude is greatest when its dis- 

 tance from the sun is least — there are exceptions to every one of these 

 particulars. 



The analogy between the physical constitution of our sun and that of comets, 

 which I have endeavored to establish, would indicate that the same agencies 

 exist in comets that exists in the sun and that it is to the conflicting or co-oper- 

 ation of these forces, to the different modes and directions of their action, that 

 we owe the variety of phenomena presented by different comets and by the same 

 comet at different times. 



FACTS AND FANCY CONCERNING COMETS. 



BY PROF. E. L. LARKIN. 



At intervals of considerable regularity th.e press is burdened with accounts 

 of impending disaster. Some dire astronomical event is always about to occur that 

 will annihilate the human species. A Chicago writer, oblivious of the laws of grav- 

 ity and motion, predicted evil to the earth to fall on June 19, 1881, and published 

 a diagram of the solar system as it would appear on the eventful day. The earth 



