THE UNIVERSE. OCEANIC DISCOVERIES. 285 



towards the poles, of a stratum of air of equal coolness, 

 mark no unimportant era in the history of our physical 

 knowledge. 



If this knowledge was favoured by observations which 

 were accidental and wholly unscientific in their origin, the 

 age which we are describing lost on the other hand, by an 

 unfortunate combination of circumstances, a great advantage 

 which it might have received from a purely scientific im- 

 pulse. The greatest physicist of the 15th century, who 

 combined distinguished mathematical knowledge with the 

 most admirable and profound insight into nature, Leonardo 

 da Yinci, was the cotemporary of Columbus, and died three 

 years after him. This great artist had occupied himself in 

 meteorology, as well as in hydraulics and optics. His in- 

 fluence on the age in which he lived was exercised through 

 the great works of painting which he created, and by his elo- 

 quent discourse, but not by his writings. If the physical views 

 of Leonardo da Yinci had not remained buried in his ma- 

 nuscripts, the field of observation which the new world 

 offered would have been already cultivated scientifically in 

 many of its parts before the great epoch of Galileo, Pascal, 

 and Huygens. Like Francis Bacon, and a full century 

 before him, he regarded induction as the only sure method 

 in natural science ; " dobbiamo comminciare dalF esperienza, 

 e per mezzo di questa scoprirne la ragione." ( 44 ) 



As, notwithstanding the wrnt of measuring instruments, 

 climatic relations in the tropical mountainous regions, the 

 distribution of temperature, the extremes of atmospheric 

 dryness and humidity, and the frequency of electric expl( ' 

 Bions, were often spoken of in the commentaries on the first 

 land journeys ; so also the mariners very early embraced 1 



