142 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



the point where it is possible to date the timbers used in these ancient 

 dwellings. 



The biological effects of ultraviolet light may be such as to stimu- 

 late certain animals to the creation of large litters, which will ac- 

 count for the fact the number of rabbit pelts returned to the whole- 

 salers by the trappers becomes a maximum near the time of sunspot 

 maximum. It is not a case of greater activity on the part of the 

 trappers, but rather a case of more rabbits to be trapped. On the 

 other hand, ultraviolet light is a penetrating radiation that seeps 

 under the cuticle of human beings and stimulates the nervous sys- 

 tem, thereby arousing the individual to unusual heights of activity 

 and achievement. With trappers thus excited in their work, it is 

 hardly possible for the cause of their enthusiasm to remain safe; 

 hence the usual number of rabbits may exist, but there is more 

 enthusiastic trapping. 



Ultraviolet radiation, as has been previously suggested, is an excit- 

 ing radiation. That large proportion of it which is not intercepted 

 by trees, plants, and human beings must of necessity find its way 

 into the earth. Whether it can be as exciting of inanimate objects as 

 it appears to be of animate ones is an open question. Yet there seems 

 to be some evidence, perhaps entirely of a coincidental nature, that 

 volcanic activity correlates with sunspot activity. Disturb the under- 

 layers of the earth's crust by an excess dose of ultraviolet radiation 

 and they may find relief by discharging their excess energy as a 

 volcanic eruption. 



Already it has been stated that ultraviolet radiation is a stimulant 

 to human beings; it may at the same time be an irritant. A Rus- 

 sian scientist suggested not many years ago, and I have seen the 

 same statement made independently at a more recent time, that great 

 international crises, such as wars, peace treaties, and other evidences 

 of international amity or friction, follow the period of sunspot activ- 

 ity with some fidelity. The basis for such a correlation may be 

 sought in the stimulating effects of ultraviolet light, prodding states- 

 men to great international concords, or, in its irritating effects, an- 

 noying them until they come to blows. The sole difficulty with the 

 correlation and with its theoretical explanation is that the world 

 seems to be in a state of international upheaval at almost any hour 

 in any year. 



A correlation of great human interest is that of sunspot activity 

 with stock market transactions and with the price of grain, wheat, 

 cotton, and other major items of exchange, the oft-discovered cor- 

 relation that prompts such letters as that quoted at the beginning of 

 this article. It is conceivable that the stimulating effects of ultra- 

 violet radiation upon humans should have much to do with the periods 

 of prosperity and depression, and with the flux of prices, not only 



