the telescope was now in the possession of several astronomers, Galileo began to have many rivals in discovery; but notwithstanding the claims of Harriot, Fabricius, and Scheiner, it is now placed beyond the reach of doubt, that he was the first discoverer of the Solar spots. From the communication which I received in 1822 from the late Dr. Robertson, of Oxford,1 it appeared that Thomas Harriot had observed the solar spots on the 8th of December 1610; but his manuscripts, in Lord Egremont's possession, incontestably prove that his regular observations on the spots did not commence ttll December 1, 1611, although he had seen the spots at the date above mentioned, and that they were continued till the 18th of January 1613. The observations which he has recorded are 199 in number, and the accounts of them are accompanied with rough drawings, representing the number, position, and magnitude of the spots.3 In the observation of Harriot, made on the 8th December 1610, before he knew of Galileo's discovery, he saw

1 See page 38.

2 These interesting MSS. I have had the good fortune of seeing in the possession of my much valued friend, the late Professor Rigaud of Oxford.

3 Edin. Phil. Journ. 1822, vol. vi. p. 317. See Rigaud's Life of Bradley, Supplement, p. 31.

three spots on the sun, which he has represented in a diagram. The sun was then 7° or 8° high, and there was a frost and a mist, which no doubt acted as a darkening glass. Harriot does not apply the name of spots to what he noticed in this observation, and he does not enumerate it among the 199 observations above mentioned. Professor Rigaud1 considers it "a misapplication of terms to call such an observation a discovery;" but, with all the respect which we feel for the candour of this remark, we are disposed to confer on Harriot the merit of an original discoverer of the spots on the

sun.

Another candidate for the honour of discovering the spots of the sun, was John Fabricius, who undoubtedly saw them previous to June 1611. The dedication of the work in which he has recorded his observation, bears the date of the 13th of June 1611; and it is obvious, from the work itself, that he had seen the spots about the end of the year 1610; but as there is no proof that he saw them before October, we are compelled to assign the priority of the discovery to the Italian astronomer.

1 See Rigaud's Life of Bradley, pp. 37, 38.

2 Joh. Fabricii Phrysii de Maculis in Sole observatis, et apparente earum cum Sole conversione, Narratio. Wittemb. 1611.

The claim of Scheiner, professor of mathematics at Ingolstadt, is more intimately connected with the history of Galileo. This learned astronomer having, early in 1611, turned his telescope to the sun, necessarily discovered the spots which at that time appeared on his disc. Light flying clouds happened, at the time, to weaken the intensity of the light, so that he was able to show the spots to his pupils. These observations were not published till January 1612; and they appeared in the form of three letters, addressed to Mark Velser, one of the magistrates of Augsburg, under the signature of Appelles post Tabulam. Scheiner, who, many years afterwards, published an elaborate work on the subject, adopted the same idea which had at first occurred to Galileo-that the spots were the dark sides of planets revolving round and near the sun.1

1 It does not appear from the history of solar observations at what time, and by whom, coloured glasses were first introduced for permitting the eye to look at the sun with impunity. Fabricius was obviously quite ignorant of the use of coloured glasses. He observed the sun when he was in the horizon, and when his brilliancy was impaired by the interposition of thin clouds and floating vapours; and he advises those who may repeat his observations to admit at first to the eye a small portion of the sun's light, till it is gradually accustomed to its full splendour When the sun's altitude became considerable, Fabricius gave up his observations, which he often continued so long that he was scarcely able, for two days together, to see objects with their usual distinctness. Fabricius speaks of observing the sun by

On the publication of Scheiner's letters, Velser transmitted a copy of them to his friend Galileo, with the request that he would favour him with his opinion of the new phenomena. After some delay, Galileo addressed three letters to Velser, in which he combated the opinions of Scheiner on the cause of the spots. The first of these letters was dated the 4th of May 1612; but though the controversy was carried on in the language of mutual respect, it put an end to the friendship which had existed between the two astronomers. In these letters Galileo showed that the spots often dispersed like vapour or clouds; that they sometimes had a dura

admitting his rays through a small hole into a dark room, and receiving his image on paper; but he says nothing about a lens or a telescope being applied to the hole; and he does not say that he saw the spots of the sun in this way. Harriot also viewed the solar spots when the sun was near the horizon, or was visible through "thick ayer and thin cloudes," or through thin mist. On December 21, 1611, at a quarter past 2 P.M., he observed the spots when the sky was perfectly clear, but his "sight was after dim for an houre."

Scheiner, in his "Appelles post Tabulam," describes four different ways of viewing the spots; one of which is by the interposition of blue or green glasses. His first method was to observe the sun near the horizon; the second was to view him through a transparent cloud; the third was to look at him through his telescope with a blue or a green glass of a proper thickness, and plane on both sides, or to use a thin blue glass when the sun was covered with a thin vapour or cloud; and the fourth method was to begin and observe the sun at his margin, till the eye gradually reached the middle of his disc.

1 The original of this letter is in the British Museum.

tion of only one or two days, and at other times of thirty or forty days; that they contracted in their breadth when they approached the sun's limb, without any diminution of their length; that they describe circles parallel to each other; that the monthly rotation of the sun again brings the same spots into view; and that they are seldom seen at a greater distance than 30° from the sun's equator. Galileo likewise discovered on the sun's disc facula, or luculi, as they were called, which differ from the common ones in their being brighter than the rest of the sun's surface.1

In the last of the letters which our author addressed to Velser, and which was written in December 1612, he recurs to his former discovery of the elongated shape, or rather the triple structure, of Saturn. The singular figure which he had observed in this planet had entirely disappeared; and he evidently announces the fact to Velser, lest it should be used by his enemies to discredit the accuracy of his observations. "Looking on Saturn," says he, "within these few days, I found it solitary, without the assistance of its accustomed stars, and, in short, perfectly round and defined like Jupiter; and such

See Istoria e Dimostrazioni, intorno alle macchie solare. Roma, 1616. Opere di Galileo, vol. v. pp. 131-293.