0f course there were not people wanting who ascribed this wonderfuldiscovery of Herschel's to pure chance. If he hadn't just happenedto turn his telescope in that particular direction on thatparticular evening, he wouldn't have seen this Georgium Sidus theymade such a fuss about at all. Quite so. And if he hadn't built atwenty-leg telescope for himself, he wouldn't have turned itanywhere at any time. But Herschel himself knew much better. "This wasby no means the result of chance," he exclaimed; "but a simpleconsequence of the position of the planet on that particularevening, since it occupied precisely that spot in the heavens whichcame in the order of the minute observations that I had previouslymapped out for myself. Had I not seen it just when I did, I mustinevitably have come upon it soon after, since my telescope was soperfect that I was able to distinguish it from a fixed star in thefirst minute of observation." Indeed, when once Herschel's twenty-leg telescope was made, he could not well have failed in the longrun to discover Uranus, as his own description of his methodclearly shows. "When I had carefully and thoroughly perfected thegreat instrument in all its parts," he says, "I made a systematicuse of it in my observation of the heaven, first forming adetermination never to pass by any, the smallest, portion of themwithout due investigation. This habit, persisted in, led to thediscovery of the quite new planet (Georgium Sidus)." As well might onesay that a skilled mining surveyor, digging for coal, came upon theseam by chance, as ascribe to chance the necessary result of such acareful and methodical scrutiny as this.