LECTURE V.
“ When they come to model keav’n.
And calculate the stars, how they will wieldThe mighty frame ; how build, unbuild, contrive,
To save appearances ; how gird the sphere,
With centric and excentric, scribbl’d o’er,
Cycle and epicycle, orb in orb.”
Milton, P. L., viii., 78.
We have giveu the first place in our discussion of the Solar System to the Sun, its all-important centre. We havedescribed the intensity of its heat, the hugeness of its size,the enormous attractive power hv which it rules the orbits ofplanet and satellite, of comet and meteorite, as they run theircourses round it. We have awarded the second place to theMoon , owing to the special interest that belongs to its closeproximity to the Earth , and the many details that we are ableto observe upon it. The various planets next claim our atten-tion. We shall find, however, that even those which approachthe Earth most closely are so far distant that very few detailscan be detected upon them comparable with those which wesee upon the Moon ; while others are so remote that ouracquaintance with them is in every respect most limited. Noteven the largest of them can emulate the Sun, either in size orheat, or in the wondrous phenomena of photosphere and spot,corona and rose-coloured prominence. And yet they are eachand all most interesting.
W r e can well imagine how the astronomer of ages long past,as he gazed at them from beneath the pure skies of the Chal-diean plains, and ever and anon saw Mercury glittering like a