254 



SCIENCE 



[N. S. Vol. XLI. No. 1050 



fact. Because, since the general atmospheric 

 circulation of the southern hemisphere is inde- 

 pendent of that of the northern hemisphere, 

 it is diifieult to imagine how the haze produced 

 by the Katmai eruption could have been car- 

 ried south of the equator. 



The meteorological observations made on 

 the summit of Pikes Peak extend from 18T4 

 to 1887. It seemed to me that the records of 

 this station — situated near the center of the 

 North American continent, on an altitude of 

 14,111 feet — may be considered most reliable 

 material for the study of the influence of the 

 dust veil of the years 1883 and 1884 upon 

 temperature conditions in the United States. 

 In this abstract it is impossible to enter 

 into the details of the discussion. I will there- 

 fore simply mention the fact that the curve of 

 the overlapping annual means observed on 

 Pikes Peak compared with other curves, and 

 the Port Darwin curve in particular, forces us 

 to admit that the formation of a pleion in the 

 states has been completely counteracted by the 

 influence of the dust veil. The mean of Sep- 

 tember, 1883, to August, 1884, must have been 

 affected the most, and this maximum effect of 

 the dust veil must have produced a lowering 

 of the annual mean temperature of about 

 3.4° F. 



The curve of the consecutive means of the 

 temperatures observed at the Batavia Observa- 

 tory confirms this result, and so do the curves 

 of Singapore, Port Blair, Colombo, Bombay 

 and Aden. 



The curves of Bombay and Port Blair, as 

 well as the Port Darwin curve, show distinctly 

 the antipleionian depressions preceding and 

 following the abraded pleionian crest. 



During the terrific eruptions of Mt. Pelee, 

 on May 8 and 20, 1902, the usual meteorolog- 

 ical observations have been made at Fort-de- 

 Prance. The mean temperatures were af- 

 fected but very slightly. The pleionian crest 

 of 1902-03 as indicated on the curve of consec- 

 utive means, has been depressed a little, but 

 certainly not more than 0.15° 0. or 0.2° F. 

 It is difiicult to judge how much the mean 

 temperatures of the individual months have 

 been affected. 



The departures of the months of May, 1902, 

 to the end of 1903 are all above the average 

 and if the slight deflections observed during 

 the period of great volcanic eruptions must 

 really be attributed to dust veils, it may be 

 presumed that the means of some months have 

 been afl^ected more than those of other months, 

 but none sufiiciently to mask the pleionian 

 character of the departures. Moreover, the 

 effect of the dust veil ceased long before the 

 complete development of the antipleionian de- 

 pression of 1904r-05. This antipleion can, 

 therefore, not be considered as a consequence 

 of the formation of the volcanic dust veil. 



The curves of the consecutive means of tem- 

 perature for Para, Cayenne and the West In- 

 dian stations Port-au-Prince, Set. Croix 

 Christianssted, St. Lucia and Barbados con- 

 firm this result. 



A very accentuated depression between 1903 

 and 1904 is also characteristic for Arequipa 

 and Mauritius, as well as St. Helena. The 

 temperature curve of Apia, Samoa Island, dis- 

 plays the same very pronounced antipleion- 

 ian depression, completely independent of the 

 formation of the volcanic dust veil of 1902. 



Assuming that the volcanic haze produced 

 by the Katmai eruption of June 6, 1912, must 

 have had the greatest effect on the tempera- 

 tures recorded in Alaska and in Canada, I 

 compared the curves of seven stations in 

 Alaska with the curves of Victoria and Ed- 

 monton, Mauritius and Arequipa. 



Since Mt. Katmai could not have affected 

 the temperature conditions of Arequipa and 

 Mauritius, it is safe to take the curves of these 

 stations as a standard. Moreover, in my previ- 

 ous publications I have shown that the consec- 

 utive means observed at Arequipa express very 

 well the normal pleionian variation and may 

 serve as a standard in all cases of comparison. 

 The occurrence of the eruption coincided with 

 the pleionian crest of Arequipa. For Arequipa 

 the consecutive mean of July, 1911, to June, 

 1912, is the highest. From then on the tem- 

 perature is decreasing till the consecutive 

 mean of October, 1912, to September, 1913. 

 The same at Mauritius. 



