954 



SCIENCE. 



[N. S. Vol. XXIII. No. 599. 



be explained, if the ions are large even in 

 comparison with the larger gradations of 

 colloidal nuclei. Fewer of these will, there- 

 fore, be captured in proportion as the ioniza- 

 tion is larger. Hence the figure shows at a 

 a corroboration of Wood and Campbell's re- 

 sults; at e an omission or inversion of the 

 periods. But the e's are much fewer in num- 

 ber, and in comparison with the amplitude of 

 the a's the e's are frequently neutral. 



In the second place the high nucleations 

 during the period of rain are noteworthy. Here 

 then few ions were present. As there is a 

 modification of the atmospheric potential 

 gradient during this time, one would favor 

 an explanation on similar lines to the ideas 

 suggested by Richardson.^ From the above 

 I could merely infer, however, that a region 

 of rain is opaque to the cosmical radiation, 

 though the periods are not wiped out. More- 

 over, the interpretation here is not straight- 

 forward and much must be left for future 

 determination. 



Since last August (1905) a systematic com- 

 parison between the dust contents and the 

 ionization of the atmosphere has been carried 

 out in this laboratory by Miss L. B. Joslin. 

 As the paper is soon to appear in the Physical 

 Review, I will merely state that no relation 

 between the two curves of monthly ionization 

 and the nucleation curve is discernible. Ion- 

 ization and dust contents of the atmosphere 

 are, therefore, not only to be referred to totally 

 different sources, but are independent of each 

 other. The origin of the former is, therefore, 

 essentially non-local. Again the positive and 

 negative monthly ionizations show curiously 

 opposed periods in the successive months 

 (August to March) which may be of relevant 

 interest. 



I may add in conclusion that if the final 

 isothermal drop of pressure in ,the fog cham- 

 ber, instead of being observed as was my cus- 

 tom heretofore, is computed from the volumes 

 of the fog and vacuum chamber and the corre- 

 sponding pressures, the data for the colloidal 

 nucleation of dust-free air found in my large 

 coronal chambers agree with the data which 



'Nature, LXXIII., p. C07, 1900. 



I endeavored to deduce from the disc colors 

 seen by Wilson in his small and unique appa- 

 ratus. In other words, the condensational 

 efficiency which I have reached in spite of size 

 is now surpassed by no other form. 



Carl Barus. 

 Brown University, 

 Providence, R. I. 



RECENT MUSEUM PUBLICATIONS. 



Report of the American Museum of Nat- 

 ural History for 1906. — ^It is difficult in re- 

 viewing the work of so large an institution, 

 whose growth extends along many different 

 lines, to select the more salient features of the 

 year, but the completion of the work of pre- 

 paring and mounting the skeleton of the great 

 dinosaur Brontosaurus may be regarded as 

 the feature of 1905. This one piece is prob- 

 ably responsible for a goodly portion of the 

 565,489 visitors, but the fine bird groups, one 

 of flamingoes and one of the bird life of the 

 San Joaquin Valley have attracted many. 



As usual, many important fossil vertebrates 

 have been secured during the year, including 

 portions of the great carnivorous reptile 

 Tyrannosaurus. 



Special attention has been given to the 

 public schools by preparing loan collections 

 and by lectures; no less than 600 bird skins 

 and 1,800 insects were purchased for the prep- 

 aration of loan collections and 400 cabinets 

 are now available for circulation. 



In concluding his report President Jesup 

 notes that this marks his twenty-fifth year of 

 service and calls attention to the progress of 

 the museum made possible by the support of 

 the citizens of New York. 



The Fourth Annual Report of the Horni- 

 man Museum notes a falling off in the num- 

 ber of visitors, primarily due to discouraging 

 irresponsible and frivolous visitors from using 

 the museum as a promenade. A noteworthy 

 feature of the museum is the veiy considerable 

 number of living animals, vertebrates and in- 

 vertebrates, shown during the year, although 

 this must necessitate much work on the part 

 of attendants. On the other hand, living 

 animals are very popular and instructive. The 

 various little handbooks issued are very good 



