382 SCIENTIFIC RECORD FOR 1884. 



as seen iu our atmosphere, are most plausibly due to selective absorp- 

 tion and reflection from minute solid particles, whose size is comparable 

 with the dimensions of the wave length of light. That these should 

 exercise also a selective influence ujjon the ultra-red rays, such as 

 would be detected by Langley's bolometer, seems highly probable. It 

 is therefore possible that the general distribution of heat over the earth's 

 surface may have been slightly affected by the novel addition to our 

 atmosphere, and especially may have had some influence upon the for- 

 mation of rain and snow ; but these influences must have been quite fee- 

 ble, and have not yet been demonst' ated from observations. On several 

 occasions during the past century liie earth has passed near enough to 

 comets or their tails to awaken inquiry as to the possible result of actual 

 contact; in fact, iu the summer of 187(J, the earth may possibly have 

 encountered the tail of the comet then visible, as several observers re- 

 ported the appearance of pinkish and ashen tints in the sky. It would 

 not be surprising if we should sometime be able to show that these sky 

 and sunset phenomena, as well as the aurora, and possibly other mat- 

 ters, such as Wilkes's red fog, may be due to the encounter of cosmic 

 meteoric matter by the earth in its annual orbir.] 



388. Dr. Neumayer publishes a large collection of data relative to 

 the twilight and other phenomena, in a series of papers extending 

 through the first volume of the Journal of the German Meteorological 

 Society. 



389. Prof. H. Krone, of Dresden, communicated through Dr. IsTeu- 

 mayer his observations and conclusions as to the nature of the twi- 

 light phenomena. 



1. A fine haze that cannot be called a fog and that does not diminish 

 the brightness of the sunshine must be the origin, and has been pres- 

 ent ever since the last of August. 



2. The twilight colors were tested by the use of a number of colored 

 glasses, which showed that the orange was absorbed by the blue, while 

 the red was not ; the red region agreed with the ring observed by Falb. 

 This ring he considers due, not to diffraction, but that it is the red re- 

 gion of the rays of less refrangibility, like the reddish, yellow and red 

 caused by the ordinary refraction at sunrise or sunset, and due to the 

 air and its vapor. 



3. A variation appeared on the evening of January 2, shortly after 

 the outburst of the orange, as an intense rosy red bundle of rays, 

 which iu a few minutes extended from the sun, then under the horizon, 

 in all directions through the red region nearly up to the zenith, and 

 sideways for 70° in the horizon either side of the sun. Similar phe- 

 nomena were seen by Krone during his journey to India iu 1875, and 

 both appearances then and now indicated that the sun's rays were 

 passing between clouds in our atmosphere beyond the horizon and 

 through a stratum of air containing more aqueous vapor, which co^n- 

 municated to them a rosy red tint. 



