GREENWICH OBSERYATORY. 
279 
the tables of Mayer, which were the first generally available for 
nautical longitudes ; 3,000 were employed by Burg for his 
tables, which so completely satisfied the conditions of a prize 
for such tables offered by the Consular Government of France, 
that the First Consul doubled the prize ; and of the 4,000 which 
were employed by Burckhardt to correct the lunar elements for 
his famous tables (which served for nearly fifty years prior to 
1862 as the basis for all navigational predictions), nearly the 
whole must have been derived from Greenwich. 
The great lunar reductions previously alluded to embraced 
nearly 9,000 Greenwich observations of the moon, made 
between the years 1750 and 1830 — a series without a parallel. 
The first fruit of their reduction was a general correction by Sir 
George Airy of the received elements of the moon’s orbit. The 
next was the discovery by Prof. Hansen, of Gotha, of two 
inequalities of long period in the moon’s motion, depending 
upon the direct and indirect action of the planet Venus. And 
what may be considered for the present as the ultimate out- 
come, was the construction by Hansen of the great Lunar 
Tables that bear his name, which represent the motions of our 
satellite with an accuracy surpassing all others, and abundantly 
sufficient for the preparation of reliable nautical ephemerides. 
Hansen’s tables are used for all the important “ Nautical 
Almanacs ” of the world, with one exception, that of America, 
for which special tables were previously prepared, embodying, 
however, the corrections derived from the long suite of Green- 
wich observations. 
If we look to other planetary tables, we find the same depend- 
ence for their data upon our National Observatory. The tables 
now used for Jupiter, Saturn and Uranus are those by Bouvard 
(1821), and they depend mainly upon the observations of those 
planets by Bradley, Maskelyne and Pond. The tables of Mercury, 
Venus, and Mars are Le Verrier’s, based chiefly upon the Green- 
wich observations from 1750 to 1830, which were, with the rest of 
the planetary observations for that period, reduced by Sir George 
Airy en masse , like the lunar observations. For the sun, Le 
Verrier’s Tables are also used ; and they depend upon a century’s 
Greenwich observations. The current tables of Neptune are 
those by Professor Newcomb, for which Greenwich found the 
major part of the observational data. Throughout the whole 
series of Planetary Tables that belong to the period of accurate 
astronomy, there is such a broad reliance for data upon Green- 
wich, and such comparatively small support derived from other 
places, that it is evident there was no excessive flattery in 
Baron Zach’s assertion that our astronomical tables would have 
been as perfect as they are if no other observatory had ever 
existed. All this we adduce, not with the idea of glorifying a 
