648 



SCIENCE 



[N. S. Vol. XXXVII. No. 956 



nite information as to the best value of the coeffi- 

 cients of the formula and as to the discrepancy 

 at the two latitudes. 

 Orbital Planes of Binaries: John M. Poor. 



The paper gave a preliminary statement in re- 

 gard to a statistical method of investigating the 

 parallelism of orbital planes of binary stars to 

 any particular plane in space. 



The several attacks upon the problem of deter- 

 mining whether the orbital planes of binary stars 

 are parallel to any particular plane in space have 

 led to no very positive indications that such paral- 

 lelism exists in the case of the best determined 

 orbits of binary stars. 



If such parallelism exists it ought to be indi- 

 cated in a statistical study of measures of binary 

 stars by the systematic variation in magnitude for 

 different parts of the sky of the correlation coeffi- 

 cient expressing the relation between position 

 angle and distance of the doubles in a limited 

 area of the celestial sphere. As this problem is 

 more easily solved in rectangular than in polar 

 coordinates, it may be put in the form of find- 

 ing the correlation between s.sinP(=x) and 

 s ■ cos P(^y). 



With a view to making a study of this question 

 along these lines the necessary computations have 

 been begun at the Shattuck Observatory, though 

 a sufficient number of correlation surfaces has not 

 yet been computed to allow conclusions to be 

 drawn. 



It is hoped that double star observers to whose 

 attention this preliminary statement may come 

 will cooperate by furnishing the writer with lists 

 of their observations published since the appear- 

 ance of Burnham's General Catalogue in order 

 that the final computations may be based on as 

 large an amount of material as possible. 

 On Climatic Changes and the Cause of Ice Ages: 



W. J. HUMPHKETS. 



Numerous geological records give evidence of 

 great climatic changes in the past, culminating at 

 times in excessive heat and aridity and at other 

 times in extreme cold and corresponding precipita- 

 tion. It appears too that the great climatic 

 changes were simultaneous and in the same sense 

 the world over — warmer everywhere or colder 

 everywhere. Hence, whatever the chief cause of 

 these effects, it must have been world-wide. 



Certain variations of long duration in the energy 

 output of the sun would meet the above conditions, 

 but the cause of such variations is not apparent 

 nor is there other evidence that they ever actually 



took place. Hence it seems well to seek for some 

 general terrestrial cause of climatic change — for 

 something in or of the atmosphere. 



More or less continuous pyrheliometric records 

 since 1880 show marked deficiencies in the amount 

 of solar radiation received at the surface of the 

 earth during the years 1884, 1885, 1886, 1903 and 

 since June, 1912. The first of these periods fol- 

 lowed the explosion of Krakatoa, the second the 

 explosion of Mount Pel6e and the third that of 

 Katmai in Alaska. The only other minimum of 

 importance, about half as great as those just men- 

 tioned, occurred in 1891 and presumably was also 

 connected with a volcanic explosion. 



Now the fine volcanic dust, roughly one micron 

 in diameter, when thrown into the isothermal 

 region of the atmosphere must settle slowly, since 

 it is above the reach of clouds, and spread over 

 all parts of the earth, as we know it did after 

 each of the above-mentioned volcanic explosions. 

 Further, the fine dust scatters the short wave- 

 length solar radiation to a much greater extent 

 than it does the relatively long wave-length earth 

 radiation. In other words, earth radiation gets 

 out through this enveloping layer of dust much 

 better than solar radiation can get in. Hence the 

 final equilibrium temperature of the earth as a 

 whole, other things being equal, necessarily is 

 lowered by the presence of a dust veil in the upper 

 atmosphere. In the cases cited above the decrease 

 of insolation seemed sufficient, if long continued, 

 even to bring on an " ice age. ' ' 



During the geological past there have been sev- 

 eral periods of great volcanic activity with inter- 

 vening ages of volcanic quiescence, just as there 

 have also been ages that were warm and dry 

 alternating with others that were cold and wet. 



Prom the above considerations it is suggested 

 that the alternate presence and absence, each for 

 long periods, of volcanic dust in the high atmos- 

 phere may have been an important if not even the 

 controlling factor in bringing about the great 

 climatic changes of which geological records fur- 

 nish abundant proof. 



Photographic Magnitudes of the Brighter Stars 

 of the Polar Sequence: Frederick H. Seabes. 

 The investigation of the magnitude scale of the 

 Polar Sequence previously reported has been ex- 

 tended by photographing the brighter stars with 

 diaphragms and screens producing apparent mag- 

 nitudes between 10.5 and 15.5. The actual mag- 

 nitudes were found by comparison with the fainter 

 stars for which the scale had previously been 



