Page:Sir William Herschel, his life and works (1881).djvu/27

Rh Having already some knowledge of the science of optics, I resolved to manufacture my own telescopes, and after many continuous, determined trials, I finally succeeded in completing a so-called Newtonian instrument, seven feet in length. From this I advanced to one of ten feet, and at last to one of twenty, for I had fully made up my mind to carry on the improvement of my telescopes as far as it could possibly be done. When I had carefully and thoroughly perfected the great instrument in all its parts, I made systematic use of it in my observations of the heavens, first forming a determination never to pass by any, the smallest, portion of them without due investigation. This habit, persisted in, led to the discovery of the new planet (Georgium Sidus). This was by no means the result of chance, but a simple consequence of the position of the planet on that particular evening, since it occupied precisely that spot in the heavens which came in the order of the minute observations that I had previously mapped out for myself. Had I not seen it just when I did, I must inevitably have come upon it soon after, since my telescope was so perfect that I was able to distinguish it from a fixed star in the first minute of observation.

"Now to bring this sketch to a close. As the king had expressed a desire to see my telescope, I took it by his command to Greenwich, where it was compared with the instruments of my excellent friend, Dr., not only by himself, but by other experts, who pronounced it as their opinion that my instrument was