Notices respecting New Books. 539 



the second part to solve these equations in the particular case of the 

 motion of the earth under the action of the sun and moon, the ap- 

 proximation being carried so far as is needed for the proof of the 

 formulae commonly given for Precession and Nutation. The trea- 

 tise is purely mathematical, and, from the nature of the subject, 

 abstruse. It is clearly and elegantly written, and well worth the 

 attention of any one interested in the question which it discusses. 



Sun-views of the Earth, or the Seasons Illustrated. By Richard A. 

 Proctor, B.A., F.R.A.S. London : Longmans, Green, and Co. 

 1867. 



A sun-view of the earth means a perspective projection of the 

 earth, the sun's centre being the point of sight and the plane of the 

 picture at right angles to the line joining the sun's centre with that 

 of the earth ; of course such a projection is practically orthographic. 

 Mr. Proctor's book consists mainly of twelve plates, one for each 

 month, on days so chosen as to show the earth when in the sol- 

 stitial and equinoctial points. Each plate contains the four views 

 corresponding to 6 a.m., noon, 6 p.m., and midnight, Greenwich 

 solar time. Each view is in fact a small map of a hemisphere, 2| 

 inches in diameter. The whole series shows extremely well the 

 general distribution of land and water on the earth's surface far 

 better than can be done by any single map. This, however, is not 

 the main object of the book, which is to enable a learner to under- 

 stand the way in which the various regions of the earth are presented 

 to the sun at different times of the year. The plates are extremely 

 good, and show what is intended as well, perhaps, as anything of 

 the kind could do. In addition to these twelve plates there are two — 

 one showing five " sun- views " of the British Isles for different times 

 of the year, the other showing the daily motion of the earth in her 

 orbit for the year 1867, and the positions of the centre and major 

 and minor axes of the orbit. There is prefixed to the work an in- 

 troduction of four pages, explaining the plates and suggesting points 

 illustrated by them. 



In addition to the above work, Mr. Proctor has also published 

 four separate plates. The first is a chart of all stars of the 

 zodiac of magnitudes superior to the 6th ; the second and third 

 show the orbits of the larger and smaller planets, their major axes, 

 lines of nodes, &c. ; the fourth gives a series of eighteen views 

 of Mars as seen at different dates, together with a chart of Mars 

 based on twenty-seven drawings by Mr. Dawes. It is by no means 

 clear whether the eighteen views are copies of actual drawings ; we 

 could have wished that Mr. Proctor had left the point clear of 

 doubt ; for if, on the one hand, they are copies of actual drawings, 

 they completely justify the chart ; if not, we are left entirely with- 

 out the means of estimating; the value of the chart. 



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