24 NECESSITY OP GENERAL 



large the bounds of our intellectual existence, and while we 

 ourselves may be living in retirement they place us in commu- 

 nication with the whole globe. Under their guidance we 

 follow with eager interest the investigations of travellers and 

 observers in every variety of climate. We accompany, in 

 thought, the bold navigators of the polar seas ; and, amidst 

 the realm of perpetual ice, view with them that volcano of 

 the antarctic pole, whose jfires are seen from afar, even at the 

 season when no night favours their brightness. The intellec- 

 tual objects, both of these adventurous voyages, and of those 

 stations of observations recently established in almost every 

 latitude, are not strange to us ; for we can comprehend some 

 of the wonders of terrestrial magnetism, and general views 

 lend an irresistible attraction to the consideration of those 

 magnetic storms, which embrace the whole circumference of 

 ttuLeacth at the same instant of time. 



Let me be permitted to elucidate the preceding considera- 

 tions, by touching on a few of those discoveries whose 

 importance cannot be justly appreciated without some 

 general knowledge of physical science. For this purpose I 

 will select instances which have recently attracted much 

 attention. Who, without some general knowledge of the 

 ordinary paths of comets, could perceive how fruitful in 

 consequences was Encke's discovery, by which a comet, that 

 in its elliptic orbit never passes out of our planetary sys- 

 tem, reveals the existence of an ethereal fluid obstructing its 

 tangential force ? A rapidly-spreading half-knowledge brings 

 scientific results ill understood into the conversation of the 

 day, and the supposed danger of collision between two 

 heavenly bodies, or of a deterioration of climate from cos- 

 mica! causes, are again brought forward in a new and more 



