162 HISTORY OF THE [1860-70 
In the same month, Schiaparelli had from his own calculations 
of the meteoric orbit made the same comparison. 
Yet again in February, Le Verrier, noting Peters’s suggestion, 
had recalculated the meteoric orbit, utilising A. S. Herschel’s 
determination of the radiant in 1866, and had found a better 
agreement with Oppolzer’s orbit. 
And in 1867 March, Adams had completed the calculations of 
the planetary perturbations, and had found that the observed 
variation of the node of the meteoric orbit could not be reconciled 
with the four shorter periods indicated by H. A. Newton, but was 
completely satisfied by the longest period. From a combination 
of five new determinations of the radiant with that derived from 
his own observations with an instrument specially devised by him, 
he deduced a definitive orbit still more closely in agreement with 
Oppolzer’s orbit for Tempel’s comet (M.N., 27 , 247). And 
thus was established the close relation between comets and 
meteors. 
Pritchard’s second Presidential Address was delivered in 1868, 
on the occasion of the award of the Gold Medal to Le Verrier, for 
his theories and tables of the four planets, Mercury, Venus, Earth, 
Mars. It was with this work that Pritchard dealt in his address. 
For his later work on the theories of Jupiter, Saturn, Uranus, and 
Neptune, the medal was again awarded to Le Verrier in 1876, 
and on that occasion Adams delivered the address. The earlier 
work led Le Verrier to infer that there existed on the one hand 
in the neighbourhood of Mercury, and on the other hand in the 
neighbourhood of Mars, sensible quantities of matter, the action 
of which had not been taken into account. In the case of Mars, 
the mass of the earth itself was at fault; it had been assumed too 
small, having been derived from too small a value of the solar 
parallax. “ With respect to Mercury, a similar verification has 
not yet taken place, but the theory of the planet has been estab 
lished with so much care, and the transits of the planet across the 
sun furnish such accurate observations as to leave no doubt of 
the reality of the phenomenon in question ; and the only way of 
accounting for it appears to be to suppose, with M. Le Verrier, 
the existence of several minute planets, or of a certain quantity 
of diffused matter circulating about the sun within the orbit of 
Mercury ” (Adams, M.N., 36 , 232). 
Considerations like these, set forth by men like Le Verrier 
and Adams, even though half a century ago, still carry weight with 
those who hesitate to accept the astronomical evidence of the 
deflection of light in a gravitational field as a crucial verification 
of the truth of Einstein’s theory ; to them the astronomical evidence