14 



BARNARD— PHOTOGRAPHIC OBSERVATIONS [April 25, 



in their progressive motion in the general direction of the comet's 

 flight. Such streams will more nearly represent the true emissive 

 velocity of the particles. 1 have shown in the Astro physical Journal, 

 Vol. XVIII. , p. 214, in the case of Borrelley's comet, that the tail of 

 a comet actually moves forward bodily as a whole both outward 

 from the sun and progressively in the direction of the comet's mo- 



LiST OF Photographs of Daniel's Comet Made w^ith the 

 Bruce Telescope. 



Approximate Position 1855.0. 



