7 68 THE POPULAR SCIENCE MONTHLY. 



Of course, if the effect of any electric discharges or other conditions 

 has been to change the potential of the particle from positive to nega- 

 tive, or the reverse, as the case may be, then the repulsion would be 

 changed into an attraction acting in the same direction as gravity. 

 In Mr. Wesley's drawings of the corona, especially in those of the 

 eclipse of 1871, the longer rays or streamers appear not to end, but to 

 be lost in increasing faintness and diffusion, but certain of the shorter 

 rays are seen to turn round and to descend to the sun.* 



It is difficult for us living in dense air to conceive of the state of 

 attenuation probably present in the outer parts of the corona. Mr. 

 Johnstone Stoney has calculated that more than twenty figures are 

 needed to express the number of molecules in a cubic centimetre of 

 ordinary air ; and Mr. Crookes shows us in his tubes that matter, even 

 when reduced to one-millionth part of the density of ordinary air, can 

 become luminous under electrical excitement. [A glass bulb about 

 four inches in diameter, kindly lent to me by Mr. Crookes, was ex- 

 hibited, in which a metal ball about half an inch in diameter formed 

 tlje negative pole. Under a suitable condition of the induction-cur- 

 rent, this ball was seen to be surrounded by a corona of bluish-gray 

 light which was sufficiently bright to be seen from all parts of the 

 theatre.] Yet it is probable that these tubes must be looked upon as 

 crowded cities of molecules as compared with the sparse molecular 

 pojmlation of the great coronal wastes. 



I forbear to speculate further, as we may expect more information 

 as to the state of things in the corona from the daily photographs 

 which will be shortly commenced at the Cape of Good Hope by Mr. 

 Ray "Woods under the direction of Dr. Gill. 



THE RELATIONS OF RAILWAY MANAGERS AND 



EMPLOYES. 



By Dr. W. T. BARNARD. 

 [Concluded.] 



IN the United States it has not been an uncommon practice for rail- 

 road corporations, looking to their own immediate immunity from 

 prosecution, to aid their servants in securing, in various ways, some 

 protection from or indemnity for the effects of injuries received in the 

 performance of duty ; but such efforts, being usually spasmodic, and 

 always conditioned upon releasing the company from all liability, have 



* For a history of opinion of the nature of the corona, see papers by Professor Nor- 

 ton, Professor Young, and Professor Langley, in the "American Journal of Science"; 

 also "The Sun," by Professor Young ; and "The Sun the Ruler of the Planetary Sys- 

 tem," and various essays, by Mr. R. A. Proctor. 



