168

HISTORICAL VIEW OF THE

discovery was now acknowledged. The tide turned;and observers began to discover more satellites: somewent as far as twelve. But a short time sufficed toshow their fallacy; and the four satellites of Galileo retained their places.

The news of the telescopic discoveries reached Eng-land in 1610. Harriot (already mentioned as a mathe-matician) sedulously cultivated astronomy, and hadthrown out, from analogical considerations, the ideathat there might exist secondary planets invisible fromtheir size and distance. He was the first to verify theresults of Galileo , and the observations were eagerlyrepeated by his friend, sir W. Lower. They jointlycarried on their telescopic researches into the variousother phenomena which now crowded upon their notice;and some highly interesting records of their labours areextant, which afford a lively picture of the intense in-terest which these discoveries had excited.* It appearsthat telescopes were made in London in 1610; but, solittle was the art founded on any good principles, thatthe observer furnished himself with a great number,out of which he had the chance of finding some whichwere good.

Among the earliest objects of attention, both to Ga-lileo and Harriot, were the spots on the sun. There isconsiderable uncertainty as to the precise date of thefirst observation of them, but little doubt exists as toGalileo ’s claim to priority; though he did not publishany account till l6'13. The description of his observ-ations is contained in a letter written in May, 1612, inwhich he speaks of having commenced these observationseighteen months before ; but we cannot here enter intoa discussion of the question. From the spots, Galileo deduced the rotation of the sun on his axis. A spotobserved by Kepler had by him been supposed to beMercury passing the sun’s disk: he renounced thisopinion immediately on learning Galileo ’s discovery.

* See prof. Rigaud’s Supplement to Bradley’s Memoirs. Oxford,; 18S3.

f Id. p. 36.