Page:Sir William Herschel, his life and works (1881).djvu/149

Rh and polishers are placed underneath the tube, let into the ground, and level with the surface of the gravelled area in which it stands." ...

The closing of the tube was done with appropriate ceremony on New-Year's-Day, 1840, when, after a procession through it by the family at Slough, a poem, written by Sir, was read, the machinery put into its present position, and the tube sealed.

The memoir on the forty-foot telescope shows throughout that prime object was not the making of the telescope itself, but that his mind was constantly directed towards the uses to which it was to be put—towards the questions which he wished it to answer.

Again and again, in his various papers, he returns to the question of the limit of vision. As has said:

"The naked eye has its limit of vision in the stars of the sixth magnitude. The light of fainter stars than these does not affect the retina enough for them to be seen. A very small telescope penetrates to smaller, and, in general, without doubt, to more distant stars. A more powerful one penetrates deeper into space, and as its power