Notices respecting New Booh. 



visible to the naked eye, adequate in plan and in execution to the 

 present state of astronomy, their value becomes greatly enhanced. 

 They form, perhaps, in a scientific point of view (with the exception 

 of the Life of Galileo and that of Kepler, each of which must be re- 

 garded as being, on the whole, of equal importance to them) the 

 most valuable single part of the works published by the Society for 

 the Diffusion of Useful Knowledge, and the precursor, we hope, of 

 many more, characterized by similar excellence. 



The projection according to which these maps are laid down, is 

 that which was suggested, for representing the sphere of the heavens, 

 by Mr. Lubbock, (under whose immediate direction, we understand, 

 they have been executed,) in his paper on the perspective represen- 

 tation of a circle, published in our fifth volume, of the present series. 

 This is the Gnomonic Projection j the stars being projected on the 

 maps in perspective; that is, as they would be, if it were possible, at 

 a given moment, by a Camera Lucida. The celestial sphere is thus 

 projected upon six planes, (each of which is represented by a map,) 

 forming the sides of a cube, the eye being supposed to be at the centre. 

 The distortion at the corners is too trifling to interfere sensibly with 

 the effect. The heavenly sphere is thus contained in six maps j and 

 the poles being taken for the respective centres of the upper and 

 lower surfaces of the cube, the sides of the cube are symmetrical, the 

 parallels of declination on them being portions of hyperbolas, and the 

 meridians straight lines j the upper and lower surfaces are also sym- 

 metrical, the parallels of declination on them being circles, and the 

 meridians straight lines. From the properties of this projection, these 

 maps have the advantage of enabling any one to find any star or con- 

 stellation with the greatest readiness j for, as stated in the " Expla- 

 nation" prefixed to them, those stars which are in the same great 

 circle in the heavens, and therefore appear to be in the same straight 

 line, are still in the same straight line in the map. 



The circles of right ascension and of declination for every degree 

 of right ascension and of declination, having been projected agree- 

 ably to this method, the stars were laid down, we are informed in the 

 tf Explanation," by Mr. W. Newton (author of the well-known globes) 

 from the Catalogue of the Astronomical Society, taking all the stars 

 in that catalogue up to the sixth magnitude, exclusive, which are 

 about all that can be seen by the naked eye. The magnitudes as- 

 signed to the stars represented are those of Piazzi, as given in the 

 Catalogue of the Astronomical Society j the difference of magnitude 

 being indicated by the number of "petals" (rays) in the asterisk 

 denoting each star ; those which vary in magnitude (taken from 

 Westphal's list, as quoted in the Bull des Scien. Math, for 1827,) 

 being distinguished by the letters Var. placed over them, as well as 

 by a different symbol from that of the invariable stars. The nebulae, 

 it is stated, are laid down from a catalogue with which the Society 

 was favoured by the kindness of Sir James South, and which had 

 been reduced to the year 1 822, by Mr. Mosley, from that given by 

 Messier in the Conn, des Terns for 1786, and from the catalogue given 

 by Lacaille, in the same volume, of the nebulae observed by him in the 



2 D 2 southern 



