DISCOVERIES IN THE CELESTIAL SPACES. 331 



earnest observation of a class of phenomena, some of which 

 could not even escape the naked eye. Simon Marius describ- 

 ed in 1612 the nebula in Andromeda, and Huygens, in 1656, 

 drew the fisfure of that in the stars of the sword of Orion. 

 Both nebulae might serve as types of a more or less advanced 

 condensation of nebulous cosmical matter. Marius, when he 

 compared the nebula in Andromeda to "a wax taper seen 

 through a semi-transparent medium," indicated very forcibly 

 the diHererkce between nebulae generally and the stellar mass- 

 es and groups in the Pleiades and in Cancer, examined by 

 Galileo. As early as the sixteenth century, Spanish and Port- 

 uguese sea-farers, without the aid of telescopic vision, had no- 

 ticed with admiration the two Magellanic clouds of light re- 

 volving round the south pole, of which one, as we have observ- 

 ed, was known as " the white spot" or " white ox" of the Per- 

 sian astronomer Abdurrahman Sufi, who lived in the middle 

 of the tenth century. Gahleo, in the Niincius Siderius, uses 

 the terms " stellce ncbulosce" and " nebidosce" to designate clus- 

 ters of" stars, which, as he expresses it, like areolce sparsiin loer 

 cethera siibfulgent. As he did not bestow any especial atten- 

 tion on the nebula in Andromeda, which, although visible to 

 the naked eye, had not hitherto revealed any star under the 

 highest magnifying powers, he regarded all nebulous appear- 

 ances, all his jiebuloscB, and the Milky Way itself, as lumin- 

 ous masses formed of closely-compressed stars. He did not 

 distinguish between the nebula and star, as Huygens did in 

 the case of the nebulous spot of Orion. These are the feeble 

 beginnings of the great works on Nebulce, which have so hon- 

 orably occupied the first astronomers of our own time in both 

 hemispheres. 



Although the seventeenth century owes its principal splen- 

 dor at its beginning to the sudden enlargement afforded to the 

 knowledge of the heavens, imparted by the labors of Galileo 

 and Kepler, and at its close to the advance in mathematical 

 science, due to Newton and Leibnitz, yet the greater number 

 of the physical problems which occupy us in the present day 

 likewise experienced beneficial consideration in the same cen- 

 tury. In order not to depart from the character peculiarly 

 appropriate to a history of the contemplation of the universe, 

 I limit myself to a mere enumeration of the works which have 

 exercised direct and special influence on general, or, in other 

 words, on cosmical views of nature. With reference to the 

 processes of light, heat, and magnetism, I would first name 

 Huygens. Galileo, and Gilbert. While Huygens was occu- 



