36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



of time, exhibit nearly every year such considerable irregular varia- 

 tions from the normal temperatures that we are at no loss to find varia- 

 tions comparable in dimensions with those we are supposing to be 

 caused by a fluctuating solar radiation. But it is only within the last 

 year that we have the series of radiation measures with which to com- 

 pare temperatures, and we now turn to recent temperatures as pub- 

 lished in the Internationaler Dekadenberichte of the Deutsche 

 Seewarte for nearly one hundred stations, for each ten-day period of 

 1903, and accompanied by normal temperatures representing the mean 

 for the same ten-day periods of many former years." .... 



" On comparing the observed temperatures of 89 stations, distrib- 

 uted over the North Temperate Zone, with the mean temperatures of 

 the same stations for many previous years, it is found that an average 

 decrease of temperature of over 2°C. actually did follow the possible 

 fall of the solar radiation, while the temperature continued low dur- 

 ing the remainder of the year. Stations remote from the retarding 

 influence of the oceans show a much greater variation than that of the 

 general mean. 



" While it is difficult to conceive what influence, not solar, could 

 have produced this rapid and simultaneous reduction of temperatures 

 over the whole North Temperate Zone, and continued operative for 

 so long a period, the evidence of solar variation cannot be said to be 

 conclusive. Nevertheless, such a conclusion seems not an unreason- 

 able inference from the data now at hand, and a continuation of these 

 holographic studies of solar radiation is of increasing interest, in view 

 of their possible aid in forecasting terrestrial climatic changes, con- 

 ceivably due to solar ones." 



"EXPERIMENTS IN AERODYNAMICS" 



We now turn from astronomy, Langley's primary field, to aviation, 

 a subject which intrigued him from boyhood's days, and in which 

 in his later years he made advances so great that he barely missed the 

 goal of achieving human flight in heavier-than-air machines. While 

 still at the Allegheny Observatory, he began experiments on the lift and 

 resistance of rapidly moving surfaces in air, employing a whirling 

 arm to carry them, and ingenious automatic instruments of his own 

 design to record the results. This work he continued at Washington, 

 resulting in a publication " Experiments in Aerodynamics." 



^' The writer is indebted to Professor Cleveland Abbe and to Dr. W. F. R. 

 Phillips, librarian of the U. S. Weather Bureau, for their aid in making accessible 

 the publications of temperature data in possession of the Weather Bureau. 



