494 Proceedings of the Royal Society 
practical computations, of every perturbation which the Solar planets 
can suffer. 
In this manner, with an energy, a constancy and an intellectual 
power never combined before in any one individual, Le Yerrier had, 
by the year 1868, produced new tables of all the inner planets 
from Mercury to Mars and in the course of them had demonstrated 
most unexpectedly, that the hitherto universally received quan- 
tity for 70 years past, of 8-56" for the Solar Parallax, was 
much too small. The effect on the astronomical world was magical. 
For years there had been a languid idea that the Solar Parallax 
value derived from the then last previous Yenus Transit, should 
be improved upon by observations of Mars at opposition ; and the 
Nautical Almanac had for half a century gone on publishing the 
appropriate ephemerides of Mars and stars near him for Opposition 
after Opposition. But few persons ever observed them ; or if they 
did, and also, like Henderson at the Cape and Taylor at Madras, 
computed the results as well, — they were not attended to. But the 
moment it was announced that Le Yerrier had found from his cal- 
culations in Physical Astronomy, that the mean Solar Parallax was 
so far from 8*56" as to be nearer to 8*95", all Astronomical Associa- 
tions were shaken to their very bases. Greenwich ran to court the 
new quantity. The Nautical Almanac adopted it with fervour : and 
half a dozen nations were presently competing with each other in 
observing and re-observing Mars’ oppositions, and always finding 
now that they gave out a quantity very like the Parallax announced 
by the great Gravitational Astronomer of France, 
But how went on things in general at the Observatoire, all this 
time 1 
For a while, wonderfully well ! If Le Yerrier had no practical 
experience himself, he knew where he could obtain it in others. So, 
the Emperor always aiding and abetting, the favoured savant had 
only to propose schemes of improvement, and the means in both 
men and money were always forthcoming to carry them out. First, 
the whole Greenwich system was imported bodily, its instruments 
imitated, its routine copied, and observing astronomers and com- 
puters of a like order procured. Then came the concentration of 
Meteorological Observations by electric telegraph from all quarters 
of Europe, and the issue of a daily Bulletin, post free to all the 
