438 



SCIENCE 



[N. S. Vol. XXXI. No. 794 



To this list the writer is now able to add three 

 of the cup-seoidiuia type of rusts as showing sexual 

 fusions. Further, a large proportion of the fiftj' 

 species of Eeeidium cups under investigation have 

 been found to show a multinucleated stage in 

 their development; this stage following, in the 

 three species above mentioned, the sexual fusions. 

 A contribution has been also made in this investi- 

 gation toward the solution of the problem as to 

 the origin and function of the peridium, it being 

 found to arise in the manner described by Rosen 

 and Richards. Some observations seem to show, 

 moreover, 'that the peridial cells exert a sort of 

 digestive function, in addition to acting as a 

 protection to the expanding aecidial mass. 



Cultures of Uredinew in 1909: J. C. Arthue, Pur- 

 due University. 



The paper covers a report in detail of the work 

 in growing plant rusts during the year 1909, this 

 being the eleventh year that the work has been 

 carried on. It is almost entirely devoted to the 

 heteroecious species of grass, sedge and cedar 

 forms. One new species of the last has been sepa- 

 rated, having seeia on Amelanchier leaves of the 

 type of Rcestelia oornuta and telia on the branches 

 of red cedar. Only one new combination was 

 worked out among the grass rusts, and none 

 among the sedge rusts, but much additional 

 information is reported on species previously 

 cultivated. 



George T. Moore, 



Secretary 



SOCIETIES AND ACADEMIES 



THE PHILOSOPHICAL SOCIETY OP WASHINGTON 



The 676th meeting was held on February 12, 

 1910, President Woodward in the chair. Two 

 papers were read. 



The Solar Constant of Radiation: C. G. Abbot, of 

 the Astrophysical Observatory of the Smith- 

 sonian Institution. 



The speaker stated that when in 1903 deter- 

 minations of the solar constant of radiation were 

 begun by the Smithsonian Astrophysical Observa- 

 tory, values ranging from Pouillet's 1.76 to 

 Angstrom's (withdrawn) value of 4.1 calories 

 were quoted in the best text-books, generally with 

 a preference for Langley's value 3.0 calories. The 

 discrepancy existed ( 1 ) because no international 

 standard scale of pyrheliometry had been estab- 

 lished, so that measurements of different observers 

 might differ by ten or even twenty per cent., 

 according to what pyrheliometer they employed; 



(2) because, since no spectrum energy measure- 

 ments had been made except by Langley (and his 

 wrongly reduced), the obseiTations made were 

 incapable of yielding the correction for loss in 

 air, and hence recourse was had to purely em- 

 pirical and untrustworthy formulae of extra- 

 polation. 



At Washington, Mt. Wilson and Mt. Whitney 

 (sea-level, one mile and three miles elevation) 

 complete spectro-bolometric and pyrheliometric 

 measurements have been made on several hundred 

 different days from 1903 to 1909. Simultaneous 

 determinations at Washington and Mt. Wilson in 

 1905 and 1906 agreed within the probable error 

 of the Washington observations. Simultaneous 

 observations at Mt. Wilson and Mt. Whitney in 

 1909 agreed within 0.5 per cent. Hence it is 

 believed that the formula of Bouger for the at- 

 mospheric extinction of monochromatic rays (such 

 as the bolometer observes) is not only theoret- 

 ically well grounded, but experimentally verified, 

 for otherwise the solar constant values obtained 

 by its aid from such different atmospheric levels 

 could hardly agree. 



Three different copies of Abbot's water-fiow 

 standard pyrheliometer have been tried on Mt. 

 Wilson with closely agreeing results. In this 

 instrument the measurements are checked by ob- 

 serving known quantities of heat electrically in- 

 troduced. The scale of the instrument appears 

 to be about three per cent, above that of the new 

 Angstrom pyrheliometers, but careful redetermi- 

 nations of the constants of the Abbot pyrheliom- 

 eters are now being made by Mr. Aldrich, and 

 these may alter the scale by as much as one per 

 cent. When verified, four silver disk secondary 

 pyrheliometers of the Smithsonian Institution will 

 be calibrated to this scale and sent abroad to 

 promote a uniform international system of pyr- 

 heliometry. 



Provisionally the mean value of the solar con- 

 stant may be given as 1.92 calories per square 

 centimeter per minute. 



Mr. Abbot also spoke briefly of the apparent 

 variations of the solar constant of radiation. 

 The Nitrogen Thermometer from Zinc to Pal- 

 ladium: A. L. Day and R. B. Sosman, of the 

 Geophysical Laboratory of the Carnegie Insti- 

 tution of Washington. Presented by R. B. 

 Sosman. 



The preliminary work of Day and Clement at 

 the geophysical laboratory developed the appa- 

 ratus for accurate measurement of temperatures 

 with the nitrogen thermometer. It consisted of 



