320 os Obituary. 
more profitably discussed when the character of the phenomena 
is more accurately ascertained. But, as the question now stands, 
all hypotheses that the observed phenomenon is produced by the 
attraction of unknown matter in the neighborhood of the sun or 
ercury must be dismissed as at least highly improbable. 
ny) 
effect is admissible. The most natural modification of this kind 
would be the addition of a term varying as the inverse third ot 
fourth power of the distance. This hypothesis can, however, be 
refuted very readily. A term of the inverse third power which, 
at the distance of Mercury, should have a value even the 
millionth part of the total gravitative force of the sun would, at 
the distance of a foot, have a value two hundred thousand times 
that of the term depending on the inverse square.- If higher 
powers than the cube were added the discrepancy would be yet 
more enormous. The existence of a term of such magnitude 1s 
out of the question.” 
“Another hypothesis which has been considered in this connec: 
tion is that of Weber’s electro-dynamic theory. According t0 
this theory the gravitative force between two bodies is expressed 
by an equation of the form 
ee 
r h? \dt h? dt’ 
in which the constant A, as is evident from the formula, must be 
a velocity. This velocity Weber has sought to determine expel 
mentally; his value is 439,450 kilometers per second. Hrom this 
datum ‘Tisserand has computed the secular variations of the 
planets. (Comptes Rendus, vol. Ixxv, p. 760. i 
_ “His results are that the only element affected with a sensible 
inequality is the perihelion, and that the secular motions of the 
rihelia of Mercury and Venus would have the following values: 
ercury, 6-28; Venus, 132, If A be the velocity of light, his 
result is, Mercury, 13’°65; Venus, 2”-86. . 
“But the actual motion has been found to be three times this. 
To produce this motion the value of A must be reduced to about 
Henry SEYBERT, an early worker in American Mineralogy ’ died 
March 3d, 1883. He contributed analyses of molybdenite from 
soberyl of Haddam, chondrodite of N. J.; and in the latter he inde 
pen dently discovered fluorine. He analyzed in 1830 the Tennesse¢ 
Oo 
of the earliest original investigators in chemistry in this country: 
Dr. Seybert’s ample fortune is said to be distributed m various 
endowments, chiefly of chemistry. 
