REVIEWS—DONATI’S COMET. 57 
* Nelson’s Atlas is an excellent and carefully executed work, of that 
class which reflects so much credit on our Scottish Geographers, and 
is an evidence of the great and increasing interest taken by the public 
in Geography”’; and he specially refers to the novel feature of the 
distances and measurements given in English miles. A no less nigh 
authority, the distinguished astronomer, Sir John Herschel, thus 
speaks of them: ‘‘I have seldom or never seen Maps more beautiful- 
ly executed. The idea of dividing each map into squares of a hun- 
dred and a thousand miles, and of inserting circles indicating the dis- 
tances from London, is a happy and useful one for popular Maps.” 
In those for Canada we might perhaps desire an additional series 
of circles, showing the distances from Ottawa, or some other point 
on our Western Hemisphere; but we have said enough to indicate 
our sincere belief that Mr. Nelson has produced an Atlas and Maps 
with such strong claims for preference by teachers, that it will 
constitute an important element of educational progress when they 
supersede all others in our Common and Grammar Schools. 
D. W. 
eee 
Annals of the Astronomical Observatory of Harvard College. Vol. 
III. Account of the great Comet of 1858. By G. P. Bond, 
Director of the Observatory of Harvard College. Cambridge: 
Welch, Bigelow, and Company, Printers to the University, 1862. 
Our readers need not be told that a comet is yet an unsolved prob- 
lem of the Universe. It is true that there has been no doubt as to 
the nature of the orbits of these strange visitants since Newton, ap- 
plying his wonderful analysis to that of 1680, compelled it to confess 
that it was describing a conic section round the sun, like the members 
of that family party which constitute the solar system, among whom 
it had intruded. In earlier days, they had been supposed to be only 
meteors existing in the earth’s atmosphere, but Tycho Brahé put an 
end to this notion, by shewing that tleir orbits lay beyond the moon. 
Kepler, who wrote a treatise on them, remarkable, as all his works 
are, for poetic imaginings and ingenious conjecture, was apparently 
puzzled by the complication of the geometrical conditions of their mo- 
tion, and was reduced in despair to propose straight lines as the best 
he could make of their paths. The true curve was, as we have said, 
demonstrated by Newton, and when, a few years later, Halley had 
found that the comet, which bears his name, was moving in an 
