Comet II. 1862. 201 



yellowish, the whole coma, but especially the sector, pale 

 greenish-blue. The extent of the ray may be one-fifth of the 

 radius of the coma. One micrometrical measure of position of 

 tho ray, about 13h. gives 280° : at lOh. it had been estimated 

 larger, perhaps 290°, but this was probably an illusion. Fig. 1 

 is a rough sketch of the head. 



August 21. Haze and clouds : but in an interval comet well 

 seen with 27 and 55. The whole is brighter; the sector more 

 distinct and defined, especially to the left : the ray seems, 

 however, somewhat less distinguished from the sector, and 

 more divergent : measurement frustrated by gathering haze ; 

 but I believe the position is much the same. 



August 22. A night of such great transparency and fine 

 definition that the comes of 110 Herculis is pretty steadily 

 visible. There has been a remarkable change. The nucleus 

 is very small and faint, and, as it were, dissolved ; barely star- 

 like even with 27, and fading more and more with intermediate 

 powers up to 460. The ray has become a kind of feather, 

 slightly curved, concave to the inverted right, having the 

 nucleus at the quill end, and expanding at the other to about 

 one-fourth of its length. Its position at llh. is, by one measure 

 taken along the chord of its general curve, 250°, by a second, 

 249°*5 ; the agreement being, of course, accidental in so nebu- 

 lous an object. The nucleus seems to melt away into the feather, 

 which springs directly and centrally out of it. The sector of 

 last night is much altered ; anything beyond 27 is too high for 

 the details of the coma ; but it seems of feebler light beyond 

 the end of the feather towards the sun, while a slight increase 

 of brightness flanks either side of the feather, but is much 

 more distinct and extensive on the left, on which side, how- 

 ever, the light seems to be indented by a kind of little bay or 

 inlet, between the end of the feather, and the furthest advance 

 of the light towards the sun. This brighter area, which may 

 be an enlargement of the left side of the sector of August 18th, 

 extends back towards the tail, till it reaches a very indistinct 

 boundary, possibly a portion of a parabola in which the nucleus 

 may stand, making an angle of perhaps 150° with the direction 

 of the feather ; the area is terminated on the left by a distinct, 

 though not defined, set-off of light, not effaced with 55, 110, 

 or even 170, which appears to form one side, of a parabolic 

 envelope ; a narrow dark channel is suspected beyond it, but 

 cannot be verified. The haze exterior to this set-off is suddenly 

 and uniformly fainter ; on the opposite side of the head nothing 

 of the kind can be traced. The nucleus and feather are yellow, 

 the surrounding light greenish-blue ; but I think the contrast 

 less marked than on August 18th. The diameter of the head 

 is about 17', but extremely indefinite. The tail is now divided 



