68 New Lunar Tubles. 



wires in the telescope B ; and adjusts die two telescopes A 

 and B, so that the intersection of the wires in each might 

 coincide. In order to render this operation more easy, the 

 wires in one of the telescopes formed a right angle ; and in 

 the other, an angle of about 10°. This being effected, he 

 puts the glasses again into the meridian circle, and measures, 

 with the circle, the angular distance of the points of intersec- 

 tion : which, by Gauss's method, must be exactly 180°; and 

 which, if found more or less, will give the quantity and di- 

 rection of the flexion. It may perhaps be imagined that, in 

 order to do this correctly, the points of intersection in the 

 wires, and the centre of the meridian circle should all be in 

 the same straight line ; a condition that would be very difficult 

 to obtain. But, this is by no means necessary, since all the 

 rays are parallel ; and the only thing required is, that you can 

 see the points of intersection through the meridian circle. 

 This will be evident by reading M. Gauss's paper. 



The event has fully answered the ingenious idea : and the 

 method gives a precision hardly to be obtained in any other 

 way. It will also determine the zenith point of the instru- 

 ment without inverting it. This method is indeed the more 

 valuable, since it can be applied at a time when (on account 

 of the weather, or from other circumstances) no observations 

 can be made. It, in fact, saves the astronomer the trouble- 

 some operation of observing by reflexion ; and gives the re- 

 sults with greater accuracy. 



I am, gentlemen, your obedient servant, 

 Gray's fnn, July 28, 1824. FRANCIS BAILY. 



NEW LUNAR TABLES. 



The new tables of the moon by M. Damoiseau have at 

 length reached this country; and their contents are highly 

 honourable to the author. They are entitled, Tables de 

 la Lune formees par la seule Theorie de V Attraction ; par 

 M. le Baron de Damoiseau, Lieutenant-Colonel d'Artillerie en 

 retraite, Chevalier des Ordres Royaux de Saint-Louis et de la 

 Legion d'Howieur, Membre adjoint an Bureau des Longitudes. 

 We have given these titles at full length, as they are equally 

 honourable to the author, as to the Government which pays 

 so much and such deserved respect and attention to distin- 

 guished merit *. This is the third set of lunar tables which 

 the French Board of Longitude has edited within these last 

 eighteen years: and already another new set is forming by 



* The Royal Academy of Sciences has recently bestowed on M. Da- 

 moiseau the prize medal, on account of his investigations relative to Encke's 

 comet. 



MM. Car- 



