90 REPORT— 1870. 



comet. This luminous cloud was visible fully ten minutes ; the changes it 

 underwent are roughly sketched below. Both the top and bottom of the 



column seemed to remain almost stationary, whilst a considerable portion of 

 the upper half drifted westward, as if carried by an east wind. 



" From the ' nucleus ' there was also a bright line extending horizontally 

 to the right, 2° or 3° long, as indicated by the red line. This seems to have 

 been almost as bright as the principal column, but much narrower, and there- 

 fore not so generally noticed. 



" My friend Jos. Walton watched it some minutes with an opera-glass, 

 and says it was as distinct as the other, 



" This must have been thrown off instantaneously by the explosion. 



" The luminous cloud, and especially the ' nucleus,' was so bright that at 

 Atlantic City, sixty miles east of this place, it was by some mistaken at first 

 for a ' fire balloon.' 



" The explosion was more than 200 mUes west of Philadelphia, at a height 

 of forty-five or fifty miles. 



" The meteor and cloud (or more generally a flash of light and the cloud 

 only) were observed at Yonkers and Harlem, near New York ; at Atlantic 

 City, and Trenton, in New Jersey; Wilmington, Delaware ; and at Phila- 

 delphia, Lancaster, Columbia, in Pennsylvania. 



" At Clarion, 250 miles west of Philadelphia (or north of west, rather), it 

 appeared in the south-east, and disappeared in the north-west ; and it was 

 followed by a sound resembling thunder, or the rolling of a heavy body 

 over a floor, I do not find that it was seen at all at any point further west. 

 Here it appeared at forty minutes after sunset. At Clarion the sun had set 

 only about twenty-five minutes before ; the general twilight was therefore 

 much stronger. This circumstance, coupled with the fact that the meteor 

 itself lasted only a second or two, not long enough for persons to look over- 

 head and see it, probably explains the fact that it does not seem to have been 

 seen generally in the region where it was vertical. 



" At places in Ohio bo far west that the meteor would appear in the east 

 so low as to be within the view of persons walking with the head in its 

 ordinary position it might be expected to be seen, but in this case the interval 

 from sunset is further reduced to about ten minutes, which is probably 

 more than sufficient to counterbalance the eff'ect of the darker background 

 in looking towards the east. 



" But a stiU stronger reason probably is that the light from this cloud was 

 principally sunlight, and that therefore the cloud would, like any other cloud, 

 be more brilliant when in the west than in the east, the effects of refraction 

 exceeding those of reflection. 



" This circumstance probably has something to do with the fact that all of 

 the above-mentioned meteors were seen in the western sky, and no corre- 

 sponding ones in the east. 



" As none have been observed later in the evening, when twilight was 

 gone, it would seem as if these meteors belonged to a group that were 

 essentially daylight meteors. 



