TITLES AND ABSTRACTS OF PAPERS 83 



mean, temperature of the sun has varied in the past, (4) the limited degree to 

 which meteorological and solar relationships have as yet been detected, and 

 (5) the contradictory nature of much of the evidence in regions outside the 

 tropics. 



^ In the light of recent discoveries these objections seem to lose much of their 

 force. In the first place, the heat of the sun is concentrated in certain por- 

 tions of the earth's surface according to the seasons. From this it would be 

 expected that extra-tropical regions, where the concentration is less than in 

 equatorial regions, would not show the same effect as those where the sun 

 acts more directly. The work of Arctowski seems to indicate that variations 

 in temperature move over the earth in waves, and that an increase in heat in 

 a given region within the tropics may not appear noticeably in other regions 

 until after a considerable lapse of time. If such a delay really occurs, it 

 would account for much of the apparent contradiction between equatorial 

 and extra-tropical regions. 



The absence of direct agreement between solar and terrestrial phenomena 

 may be accounted for in part in another way. The recent work of Hum- 

 phreys, Fowle, and Abbott seems to show that the presence of volcanic dust in 

 the atmosphere may exclude a measurable amount of solar radiation. The 

 disturbing element thus introduced does not seem to be sufficient to account 

 fois the main climatic variations during the period since observations are 

 available, but it accounts for many apparent discrepancies between solar and 

 terrestrial phenomena. "' " ^ 



Among the various elements which combine to make up the earth's climate 

 none is more difficult to explain than the cyclonic storms which dominate the 

 weather of Europe and America. These have recently been studied by two 

 new methods. The first is the measurement of the growth of trees, by which 

 our knowledge of climatic variations is extended over a much wider range 

 than hitherto, both in Europe and America. The second is Kullmer's method 

 of analyzing the number of cyclones passing over different portions of the 

 temperate zone. Both methods appear to show" a direct relationship between 

 the number of sun-spots and the number of storms. Melldrum and others 

 have shown a similar relationship in the case of tropical hurricanes. More- 

 over, the work of Kullmer shows that not only the number of storms, but 

 their concentration in certain areas varies in response to sun-spots. Hence il: 

 appears that changes in solar spottedness, even though unaccompanied by any 

 great change in the mean solar temperature, may influence the circulation of 

 the earth's atmosphere and thus produce distinct changes of climate. The 

 terrestrial changes, also, do not seem to demand any great change in the 

 earth's mean temperature for the redistribution of solar and equatorial tem- 

 peratures occasioned by a shifting of the location of storm tracks, and a 

 change in their number would cause pronounced climatic variations, even if 

 the mean temperature changed but slightly. 



Presented in full without notes. 



VOTE OP THANKS 



A most hearty vote of thanks was passed to the authorities of Prince- 

 ton University, the Department of Geology, and the local committee for 



