Apeil 17, 1908] 



SCIENCE 



625 



intersections of the parallel lines, which cor- 

 responds to its proper group and the extent of 

 its variation. The resulting system of dots 

 shows at a glance the extent and trend of the 

 variations in any of the groups, and in a 

 much more graphic manner than an examina- 

 tion of the specimens, or tables of measure- 

 ments, or descriptions. 



In the diagram, groups A^ and A_^ show the 

 possession of similar characters, groups A^ 

 A^ A^ and A„ possess another set of char- 

 acters. Some specimens in each group show 

 an overlapping of characters or intergrada- 

 tion. The two major groups thus show a sub- 

 specific relation to each other. 



M. C. Marsh, 

 Recording Secretary 



THE PHILOSOPHICAL SOCIETY OP WASHINGTON 



The 648th meeting was held March 28, 

 1908, President Bauer in the chair. 



Dr. C. G. Abbot presented a paper entitled 

 *' Total Eclipse Observations of January 3, 

 1908," giving an illustrated account of his 

 trip to Mint Island in the south Pacific Ocean, 

 via California and Tahiti, for the purpose of 

 observing the recent solar eclipse. His prin- 

 cipal object was to ascertain the comparative 

 brightness of the solar corona and the sun, 

 and to compare the quality of the radiation 

 of the corona with that of the sun, the moon 

 and the sky. He was successful in measuring 

 the brightness of the corona at five points 

 with the bolometer, and by interposing a 

 screen of asphaltum varnish determined 

 roughly the proportion of its radiation which 

 falls in the visible spectrum. At brightest 

 the corona was little more than 1/1,000,000 

 as bright as the sun, but the quality of its 

 radiation as tested by the asphaltum screen 

 differed little from that of the sun. The re- 

 sults are perhaps best explained by considering 

 the corona to shine mainly by reflected sun 

 rays. 



Informal Communications 



Professor C. P. Marvin spoke of the seis- 

 mograph records of the recent Mexican earth- 

 quake (March 26, 1908) which had been ob- 

 tained from the Omori and Marvin types of 

 seismographs at the U. S. Weather Bureau, 



and pointed out significant differences in the 

 amplitudes and the character of the wave 

 motion as recorded by the two forms of instru- 

 ment which were installed under exactly sim- 

 ilar conditions. 



The secretary read a communication pre- 

 pared by Professor Cleveland Abbe, giving 

 the following abstract of the results of a com- 

 putation, by Professor H. A. Peck, of Syra- 

 cuse University, of the orbit of the meteor of 

 Christmas eve, 1873, based on the data in the 

 report of the meteor committee.' 



Pirst, the point of disappearance was de- 

 termined from records at four of the best 

 observing stations, following the method given 

 by Bauschinger. The resulting location is: 

 Longitude, 0° 57.8' west of tlie dome of the capitol. 

 Latitude, -f 38° 42'. 



Altitude, between 5 and 9 miles — ^the mean of 

 which, 7 miles, is adopted. 



With this determination as a foundation the 

 position of the radiant point was determined 

 by the method of least squares from the ob- 

 servations at twelve good stations. The result 

 is: 



A (right ascension of radiant) 66° 55' 



D (declination of radiant) -t- 29° 51' 



This last result may be otherwise expressed 

 thus: The bearing and apparent angular alti- 

 tude of the radiant point, as seen by an ob- 

 server at the point and moment of disappear- 

 ance, would be 



Azimuth S. 86° 55' E. 



Altitude 56° 27' 



The first appearance of the meteor, or the 

 beginning of its visible path, may plausibly 

 have been at about 130 miles above a point in 

 latitude 38.6°, longitude 76.3°, or above the 

 mouth of the Choptank Eiver, Maryland. The 

 corresponding le.-gth of the visible path would 

 be 154 miles and the velocity relative to the 

 earth's center 38.5 miles per second. 



The computation of the path relative to the 

 sun and the ecliptic gives the true radiant 

 point : 



Longitude (X) 50° 47' 



Latitude (|3) -f- 6° 26' 



Velocity 50 miles per second. 



^Bull. Phil. Soc, 1877, Vol. II., pp. 139-161. 



