Head of Donati's Comet.
X.
THE STRUCTURE OF COMETS.
The comet of Donati, which presented so imposing a spectacle in our northern hemisphere in 1858, strongly revived the popular interest in such phenomena. Few of the present generation had an opportunity of gazing on any comet of remarkable splendour and magnitude. Our fathers told us of the wonderful comet of 1811, spanning half the circuit of the heavens with its tail, and hanging over
