60 REVIEWS—DONATI'S COMET. 
made upon the great comet of 1858, from the first glimpse caught of 
it by Donati at Florence, on June 2nd, when it showed itself as “a 
little nebulosity having a diameter of about three minutes, and with 
the illumination equally diffused throughout its surface,” tracing 
night by night its gradual development and extinction, till it vanished 
from the gaze of Maclear at the Cape of Good Hope, on Feb. 26, 
1859, when its diameter had become less than one minute. Many 
circumstances were combined to render the observing of this comet of 
peculiar value—its position relative to the earth got rid to a great ex- 
tent of the effects of foreshortening, and an unusual continuance of 
fine weather on both sides of the Atlantic, and the absence of moon- 
light at the most critical periods, rendered available more opportunities 
than are commonly afforded. Professor Bond, of whose ability America 
may well be proud, and who has added lustre to the reputation which 
his lamented father had well earned for the observatory of Har- 
vard, has admirably performed the duty he proposed to himself, 
by collecting all the scattered mass of information to be found in the 
reports of the numerous astronomers from all parts of the globe (no 
less than 84 different observers are quoted); it adds to the value of 
his work that he has quoted them each in their own language and 
words (though a lazy reader may wish he had translated here and 
there, especially as Danish and Swedish are not given every body to 
know), and still more that by classifying the phenomena he has 
enabled us to consider each separately, without extraneous distraction, 
and has further made the necessary calculations and reductions with 
his well-known skill and accuracy ; it is only justice to Professor Bond 
to add that his own observations at Harvard form the most valuable 
portion of the whole series. Nor can we refrain from giving our 
humble approbation of the thorough manner in which the volume 
has been sent to press, of the fine typography and extremely beauti- 
ful engravings ; and when we add that the whole expense has been 
defrayed by the private liberality of some leading citizens of Boston, 
our readers will join us in admiration of such noble liberality dis- 
played during this dark epoch of their unhappy country. 
A comet may be divided into four parts; First, the nucleus, a star- 
like point, sometimes a disc; Second, the coma or wig, a luminous 
haze surrounding the nucleus, and generally increasing in intensity 
towards the centre :—these two constituting the head; Third, the ¢azl, 
directed from the sun and widening as it recedes, brightest at the edges, 
