THE UNIVERSE. OCEANIC DISCOVERIES. 283 



circumstances, for example on the coasts of Peru in the 

 season of constant fogs (garua), the latitude might be de- 

 termined from the inclination of the magnetic needle with 

 sufficient accuracy for the purposes of navigation. I have 

 dwelt so long on these details, with the view of shewing 

 that all the points with which we are now occupied, in re- 

 ference to an important cosmical subject (with the exception 

 of the measurement of the intensity of the magnetic force, 

 and of the horary variations of the declination), were already 

 spoken of in the 16th century. In the remarkable map of 

 America appended to the Eoman edition of the Geography 

 of Ptolemy in 1508, we find to the north of Gruentlant 

 (Greenland) a part of Asia represented, and " the magnetic 

 pole" marked as an insular mountain. Martin Cortez, in 

 the Breve Compendio de la Sphera (1545), and Livio Sa- 

 nuto, in the Geographia di Tolomeo (1588), place it more 

 to the south. Sanuto entertained a prejudice which, strange 

 to say, has existed even in later times, that a man who 

 should be so fortunate as to reach the magnetic pole (il 

 calamitico), would experience there "alcun miracoloso stu- 

 pendo effetto." 



In the department of the distribution of temperature and 

 meteorology, attention was already directed, at the end of the 

 15th and beginning of the 16th centuries, to the decrease of 

 temperature ( 436 ) with increasing western longitude, (the in- 

 flection of the isothermal lines) ; to the law of rotation of the 

 winds ( 437 ) generalized by Francis Bacon ; to the diminution 

 of atmospheric moisture and of the quantity of rain> caused 

 by the destruction of forests ; ( 438 ) and to the decrease of tern- 

 perature with increasing elevation above the level of the 



VOL. II. U 



