HISTORY OF PHYSICAL ASTRONOMY.

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the inferior conjunctions and stationary points of 1850-52. The conductof the observations has been assigned to Lieutenant Gilliss, a youngastronomer ivlio has already signalized himself in a most praiseworthymanner. It is to be hoped that the result of this expedition will prove tobe as conducive to the advancement of astronomical science as the expedi-tion itself is creditable to the Government under whose auspices it has beenundertaken.

When Galileo first directed his telescope to the sun, he was surprisedto find that the surface of that luminary, instead of presenting a uniformappearance, according to the opinion universally entertained by philoso-phers, was diversified with a number of dark spots exceedingly irregularboth in form and magnitude. When watched attentively for some daysthese phenomena were perceived to be in a state of constant change. Insome instances two or three spots would unite together and form one largespot; and on the other hand it happened not unfrequently that a spot ofconsiderable magnitude would break up into two or three smaller ones.In the latter case the spots generally diminished with more or less rapidity,and finally disappeared altogether, when they were succeeded by others ofthe same irregular and fleeting nature. This remarkable discoveryinflicted one of the most effective blows which had yet been dealt againstthe ancient philosophy by the progress of scientific research; for it wasone of the fundamental doctrines of Aristotle that the heavens are incor-ruptible and immutable; and, therefore, that the surfaces of the celestialbodies are destitute of any physical changes analogous to those whichcharacterize the operations of nature on the surface of the earth. Theannouncement of the existence of spots on the sun was therefore receivedby the adherents of that philosophy with feelings of deep mortification,and various attempts were made to demonstrate its fallacy. By some thespots were alleged to be spurious phenomena arising from the impuritiesin the glasses with which the observations were made. By others theywere maintained to be planets revolving round the sun at small distancesfrom his surface, for when watched some days they were all found to havea motion on his disk from east to west. Observations made with differentglasses sufficed to disprove the former of these assertions. With respectto the latter, a fatal objection to it consisted in the irregular aspect andchangeful character of the spots.

Although the name of Galileo is more intimately associated with thediscovery of the solar spots than that of any other philosopher, it wouldappear that one of his contemporaries at least arrived also at a knowledgeof these interesting phenomena by original observation. Nay, it has evenbeen alleged that the illustrious Italian was anticipated on this occasion byan astronomer of Germany . It is incontestable that the earliest publica-tion which contains an account of the solar spots is due to John Fabricius,a nephew of David Fabricius, the astronomer and intimate friend ofKepler. The dedication of this work* is dated June 13, 1611. Theauthor asserts that the solar spots were observed by him from the com-mencement of the current year. The work contains internal evidencethat some of the observations of these phenomena must have been madeat least three months anterior to the date of dedication. Another ofGalileo’s contemporaries who asserted that he had discovered the spotsby his own observations was Christopher Schemer, a German Jesuit ,

* Johannis Fabricii Phrysii de Maeulis in Sole Observatis t &c. Witteburgi, 4to, 1611.