THE UNIVERSE. DISCOVERIES IN THE CELESTIAL SPACES. 335 



the many wants of science and of navigation will some 

 day be satisfied by the execution of this plan so often de- 

 sired by me. May the year 1850 deserve to be marked 

 as the first normal epoch in which the materials of a " mag- 

 netic map of the world" shall be assembled; and may per- 

 manent scientific institutions impose on themselves the 

 duty of reminding, every quarter of a century, a Govern- 

 ment favourable to the prosperity and progress of naviga- 

 tion, of the importance of an undertaking the great cos- 

 mical value of which is attached to long-continued repe- 

 titions ! ( 514 bis -) 



The invention of instruments for measuring temperature 

 (Galileo's thermoscopes ( 515 ) of 1593 and 1602 were de- 

 pendent concurrently on changes of temperature and on 

 variations in the pressure of the external air) first gave 

 rise to the idea of investigating the modifications of the 

 atmosphere by a series of connected and successive obser- 

 vations. We learn from the Diario of the Academia del 

 Cimento, which, during the short continuance of its acti- 

 vity, exercised so happy an influence on the disposition 

 for experiments and researches on a systematic plan, that, 

 as early as 1641, observations of temperature were made 

 five times a day at many stations, ( 516 ) with spirit ther- 

 mometers similar to our own ; at Florence, at the Convent 

 degli Angeli, in the plains of Lombardy, in the mountains 

 near Pistoia, and even in the elevated plain of Innspruck. 

 The Grand Duke Ferdinand II. charged the monks of many 

 convents in his states with this task. ( 517 ) The tempe- 

 ratures of mineral springs were also determined, giving 

 occasion to many questions respecting the temperature of 

 the earth. As all telluric natural phenomena, i. e all the 



