236 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



Table I. — Negative drop. 



[Distance between cross hairs = 1.010 cm. Distance between plates = 1.600 cm. Tem- 

 perature=24.6° C. Density of oil at 25° C. =0.8960. Tiscosity of air at 25.2° C.= 

 0.0001S36.] 



