Solar Physics. 451 



several accounts of his observations and speculations, and shall 

 continue to do so, as they are of great value in indicating a 

 very important class of facts, and in suggesting theories which, 

 whether finally accepted or not, may be made of great use in 

 suggesting particular lines of inquiry and observation. The 

 Kew photographs, of which we gave specimens in vol. v., p. 

 450, afford admirable records of the appearance and disap- 

 pearance of spots; but they are not intended as pictorial 

 representations. M. Chacornac's figures possess this character, 

 and so do the large drawings for which Mr. Howlett has won 

 an honourable amount of fame. Several German observers 

 contribute frequent papers to the Astronomische Nachrichten, 

 and Schwabe's laborious observations, together with earlier 

 observations by Professor Wolf, of Zurich, are amongst the 

 materials at the disposal of Mr. Warren De La Rue and his 

 coadjutors, who have just put forth the first series of their 

 Researches on Solar Physics, of which we shall proceed to give 

 an account. 



The writers begin by remarking on the marked difference 

 between the knowledge we possess of our luminary and of our 

 satellite ; and they say, " Could we imagine an observer sud- 

 denly transported to the neighbourhood of Tycho or Coperni- 

 cus, he would probably be better prepared for the appearance 

 presented to him than he would be if placed suddenly in. 

 equatorial Africa or central Australia." With the sun the case 

 is different ; for though the spectroscope enables us to detect 

 the presence of certain familiar substances, the daily outpour- 

 ing of solar light and heat remains a great mystery ; and " it 

 has not been finally decided whether this luminosity proceeds 

 from the sun's solid body, or from an envelope which surrounds 

 it. Indeed, so strange and unaccountable are many of the 

 features presented to us, not only by our own sun, but by 

 many of the stars, that it has even been conjectured that these 

 bodies exhibit instances of the operation of some force of the 

 nature of which we are yet ignorant." 



In the history of solar physics, Galileo first attempted to 

 make use of sun spots to determine the rotation of our lumi- 

 nary. After this, in 1777, Alexander Wilson, Professor of 

 Astronomy in Glasgow, advanced the opinion, that the spots 

 were cavities in a luminous photosphere. Schwabe, of Dessau, 

 demonstrated, from forty years' observations, that " the num- 

 ber of spots which break out on the sun's surface is not the 

 same from year to year, but has a maximum about every ten 

 years — a remark which led General Sabine to observe that the 

 various epochs of spot frequency were also those of magnetic 

 disturbance in our own globe." To Mr. Carrington, the writers 

 on Solar Physics ascribe the next important step. He 



