THE SUN'S SPOTS. 379 



of a large number of observations of those maculae, which, 

 from their permanence of form, and invariability of position 

 in reference to other co-existent spots, may form the basis 

 of reliable observations. 



Although solar maculae may be more frequently seen by 

 the naked eye than is generally supposed, if the Sun's disc 

 be attentively observed, there yet occur not more than two 

 or three notices of this phenomenon between the beginning 

 of the ninth and of the seventeenth centuries, on the accuracy 

 of which we can rely. Among these I would reckon the 

 supposed retention of Mercury within the Sun's disc for eight 

 days, in the year 807, as recorded in the annals of the 

 Frankish kings, first ascribed to an astronomer of the Bene- 

 dictine order, and subsequently to Eginhard; the 91 -days 

 transit of Venus over the Sun, under the Caliph Al-Motas- 

 sem, in the year 840; and the Signa in Sole of the year 

 1096, as noticed in the Staindelii Chronicon. I have during 

 several years made the epochs of the mysterious obscurations 

 of the Sun which have been recorded in history, or, to use 

 a more correct expression, the periods of the more or less 

 prolonged diminution of bright daylight the subject of 

 special investigation, both in a meteorological and a cosmical 

 point of view. 23 Since large numbers of solar spots (Hevelius 



22 Although it cannot be doubted that individual Greeks 

 and Romans may have seen large Sun-spots with the naked 

 eye, it is, at all events, certain, that such observations have 

 never been referred to in any of the works of Greek and 

 Roman authors that have come down to us. The passages of 

 Theophrastus, De Signis, iv. 1, p. 797; of Aratus, Diosem. 

 V. 90-92; and of Proclus, Paraphr. 11, 14, in which the 

 younger Ideler (Meteorol. Veterum, p. 201, and in the Com- 

 mentary to Aristot. Meteor, torn. i. p. 374) thought he could 

 discover references to the Sun's spots, merely imply that the 

 Sun's disc, which indicates fine weather, exhibits no difference 

 on its surface, nothing remarkable (p;c>e 71 aij/na 0e/aot), but, 



