i 8 KANSAS CITY REVIEW OF SCIENCE. 



a deeper significance and greater interest, and it is felt that the theories advanced 

 and ably maintained by prominent astromomers and physicists are probably in- 

 suflficient and untenable. 



It was known from actual observation that clouds of volcanic dust could 

 produce, temporarily, various and brilliant colors in the atmospheric reflections. 

 It seemed possible, even plausible, that a comparatively immense volume of such 

 dust projected into the atmosphere by the Krakatoa eruption, might remain sus- 

 pended for a considerable period, gradually settling to the earth and the effect 

 entirely disappearing within a few months. Such, however, has not been the 



case. 



Over twelve months have passed and although the intensity and duration of 



the " afterglow " subsided considerably after two or three months, it has since 

 that time continued with considerable uniformity. The dust theory has been 

 largely supported by the discovery, as reported in different localities, of dust sim- 

 ilar in appearance to that from the volcano, but we should not forget that this 

 '' meteoric dust" had been collected and examined in many places long before 

 the outburst of Krakatoa. The coincidence in point of time — these appearances 

 having commenced soon after the terrible convulsion — has perhaps been in real- 

 ity the principal reason for attributing their origin to that event. 



The fact of the observation of the phenomenon successively at points more 

 and more remote westward from the Indian Ocean has also been cited as favor- 

 ing that view ; but such progression in the phenomenon would probably be the 

 case whatever the cause which produced it, and the observations are too incom- 

 plete and uncertain to be at all conclusive. It is becoming very difficult to 

 believe that the bowels of the earth have been so suddenly emptied to such an 

 extent as the phenomena would demand upon that theory, or that the pulverized 

 obsidian or whatever the discharge may be, could remain permanently in suspen- 

 sion. It therefore looks as if that theory must be abandoned. 



One other opinion has been advanced and strongly advocated by a few 

 scientific and many very unscientific writers, viz : that the phenomena are due 

 to the presence of aqueous vapor in the atmosphere. They seem, without ex- 

 ception, to have quite forgotten that the same appearances have not been of 

 common occurrence hitherto and must therefore be accounted for if at all, by 

 some new or very unusual conditions. 



A communication published in the November number of the Review advo- 

 cates this view. The writer assumes that the coloration is produced wholly by 

 the moisture in the atmosphere, and curiously enough, that the less the quantity 

 of moisture, the greater the effect produced ! That would seem to be sufficient at 

 once to settle that theory so far as his argument is concerned. His first remark 

 also, concerning the "great commotion" produced in the scientific world, though 

 greatly exaggerating that "commotion," shows that he is aware that the event is 

 something new and altogether unusual, which aqueous vapor in great and small 

 quantities certainly is not. Mr. Noyes suggests no recent change in terrestrial 

 conditions except the development of the modern " Weather-Map." This, as he 



