* 
Chemistry and Physics. 141 
observations, comprised in twenty g 
than tw deb complete oscillations, were made with this 
apparatus, one being in the summer months of July and August, 
the other in the fall and winter months of 1872-73. The summer 
series gave for the mean density of the earth 5°56; the winter 
series 5°50. The mean variation was 1°25 per cent for the sum- 
mer, and 1°5 per cent for the winter series. The difference in the 
. . 
sf n 
law of variation, the mean density of 5°55 is obtained. j 
thors take 5°56—the mean of the summer determinations given 
above,—as accurate to within one per cent.— Compt. Rend., \xxvi, 
954, April, 1873. FB. 
2. On Spectral Lines of Low Temperature.—The Marquis of 
Sartspury has observed that there appears in the tube of a ther- 
not be due to heat. This light then, appears at a temperatu 
O° . 
cleanliness in preparing the instrument, the suriace of glass 
Seeming to attract readily thin films of grease. 4n a dirty 
thermometer, one or two additional lines appeared in the green. 
ese results are interesting since they show that carbon vapor 
becomes luminous under electric influence at a lower temperature 
