There is certainly no one body in creation which is so emphatically pre-eminent as the Sun. Whether or no there are stars which are suns—centres of systems serving in their degree the purposes served by our Sun, I need not now pause to enquire, though I think the idea is a very probable one; but of those celestial objects with which our Earth has a direct relationship, beyond doubt the Sun is unquestionably entitled to the foremost place. It is, as it were, the pivot on which the Earth and all the various bodies comprising the Solar System revolve in their annual progress. It is our source of light and heat, and therefore may be called the great agent by which an Almighty Providence wills to sustain animal and vegetable life. The consideration of all the complicated questions which arise out of these functions of the Sun belongs to the domain of Physics rather than that of Astronomy; still these matters are of such momentous interest that an allusion to them must be made, for they ought not to be lost sight of by the student of Astronomy. Half a century ago the actual state of our knowledge respecting the Sun might without difficulty be brought within the compass of a single chapter in any book on Astronomy, but so enormous has been the development of knowledge respecting the Sun of late years, that it is no longer a question of getting the materials properly into one chapter, but it is a matter of a whole volume being devoted to the Sun, or even, as in the case of Secchi, of two large octavo volumes of 500 pages each being required to cover the whole ground exhaustively. The reader will therefore easily understand that in the space at my disposal in this little work nothing but a passing glimpse can possibly be obtained of this great subject. It is great not only in regard to the vast array of purely astronomical facts which are at a writer’s command, but also on account of the extensive ramifications which the subject has into the domains of chemistry, photography, optics and cognate sciences. I shall therefore endeavour to limit myself generally to what an amateur can see for himself with a small telescope, and can readily understand, rather than attempt to say a little something about everything, and fail in the effort.