2G4 PROGRESS OF METEOROLOGY IN 1889. 



more particularly ou astronomical detiuitiou. Here again it seems to 

 have possessed a selective absorption of the red rays, for in two separ- 

 ate lunar eclipses, 1884 and 1885, the usual coppery tint of the moon 

 was conspicuously absent. He then passes on to the peculiar large 

 corona round the sun and moon, which was first observed by Mr. Bishop, 

 at Honolulu, on September 5, and which, though less striking than the 

 twilight glow, was, if anything, more uncommon, more constant, and 

 more prolonged in duration. It was a true diffraction corona with a 

 reddish border, and of almost exactly the same size as the ordinary ice- 

 halo, viz, 45° in diameter. It lasted from September 5, 1883, up to 

 October 15, 1886, since which date it has entirely disappeared. Its di- 

 ameter has afforded an approximate determination of the mean radius 

 of the smaller dust particles composing the haze, which Mr. Archibald 

 calculates to be 0.00006 of an inch. 



In section iii, Mr. Russell works out the geographical distribution of 

 the optical phenomena, including blue suns and glows, up to the end of 

 1883, by which time they had virtually covered the whole earth. The 

 general conclusion is that the phenomena all propagated themselves 

 (with the exception of a narrow ofl'shoot towards Japan) at first due 

 west from Java, at a rate of about 76 miles an hour right round the 

 earth parallel to the equator, and in a band symmetrically disposed for 

 16° on either side of the latitude through Krakatoa. A second circuit 

 with wider limits, 30° north and south of Krakatoa, was traced at the 

 same rate, after which the motion became indistinguishable. They then 

 gradually spread in latitude, and ultimately the haze which caused 

 them appears to have invaded our latitudes, like the anti-trade, from 

 southwest to northeast. These circumstances may be best realized 

 from a survey of Mr. Russell's maps, especially that showing the suc- 

 cessive limits of the appearances for the first 9 days succeeding the 

 eruption. The march of the optical phenomena which is shown in Mr. 

 Russell's maps is the only direct evidence we have of the fact that at 

 100,000 feet above the earth, in the immediate vicinity of the equator,, 

 the air in August, and probably, as Mr. Archibald shows, at other times^ 

 moves in a rajjid and constant current from east to west. Both in sec- 

 tion III (fc), and section vii, he discusses this question in detail and 

 shows its agreement with the theory of the general circulation of the 

 atmosphere, as well as the motions of the upper clouds so far as they 

 have been observed. 



In section iv, Mr. Archibald investigates the height of the stratum, 

 from observations in all parts of the world where the durations of the 

 primary or secondary glow have been recorded with any attempt at 

 accuracy. Proceeding on the hypothesis that the primary glow was a 

 first reflection of the sun's rays by the stratum, and the secondary a 

 reflection of the primary glow, for which ample evidence is adduced, he 

 concludes that the height of the upper or middle part of the stratum 

 above the earth diminished from 121,000 feet in August, 1883, to 64,000 



I 



