192 SCIENCE AND THE HUMAN MIND 



During the second half of the eighteenth century, 

 the systematic exploration of the world proceeded 



Scientific apace, and much of it was undertaken 

 Exploration. j n a t rue scientific spirit. Captain James 

 Cook (1728-1779), born at Marton in Yorkshire, and 

 present at the capture of Quebec in 1759, had 

 published work on a solar eclipse in the Philo- 

 sophical Transactions of the Royal Society, before 

 he sailed in the Endeavour to observe the transit 

 of Venus from the South Pacific Ocean. His later 

 voyages of discovery were conducted with keen 

 appreciation of their opportunities for the advance- 

 ment of knowledge, and he was one of the earliest 

 recipients of the Copley gold medal of the Royal 

 Society. 



In any account of the progress of knowledge during 

 the period under review, it is not easy to classify the 

 work of Baron von Humboldt (1769-1859), the dis- 

 tinguished Prussian naturalist and traveller, who for 

 a great period of his life found his most congenial 

 home in Paris. He spent five years in exploring the 

 continent of South America and the seas and islands 

 of the Mexican Gulf. It was on observations collected 

 during this expedition that he laid the foundations 

 of the claims of physical geography and meteorology 

 to be considered as accurate sciences. Von Humboldt 

 was the first to map the earth's surface in lines of 

 average equal temperature isothermal lines by which 

 he obtained a method of comparing the climates of 

 different countries. He studied the rate of decrease 

 of temperature with increase of height above the sea- 

 level, during his ascents of Chimborazo and other 

 peaks of the Andes. He considered the origin of 



