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with a nerve-net, and animates a continent with thought 

 and sympathy? Who could have pictured to himself 

 the marvellous growth of the young giant force which 

 James Watt summoned into being, and which no sneer 

 of the scoffer could strangle in its cradle ? When Huy- 

 ghens first observed, in 1678, the phenomenon of the 

 polarization of light in the divided beam produced by a 

 doubly refracting crystal, or when Mains, in 1808, 

 detected a similar modification while observing the light 

 of the setting sun reflected from the windows of the 

 Luxembourg, through a crystal of Iceland spar — who 

 could have foreseen that the illustrious Arago would, by 

 his discovery oi colored jpolarization, be led to discern, by 

 means of a small fragment of the same crystal, whether 

 solar light emanates from a solid body, or a gaseous cov- 

 ering ; or whether comets shine by direct or reflected 

 light ? When the contemporaries of Robert Hooke ridi- 

 culed his experiments with the ^^swing-swangs," they 

 little dreamed that the pendulum would one day enable 

 the physical philosopher to determine the figure and 

 weight of the earth, and even to sound, as it were, its 

 unseen depths and reveal to us, in some measure, the 

 internal constitution of its strata. When the alchemists, 

 centuries ago, observed that one of the salts of silver 

 was blackened by exposure to light, who could have anti- 

 cipated, that the fleeting images of a camera-obscura 

 would be rendered permanent, or that the sunbeam con- 

 tained in it a pictorial power far surpassing in truthful- 

 ness the most elaborate efforts of human ingenuity ? 



It thus appears evident that the smallest contribution 

 to knowledge adds something to the enduring structure 

 of scientific truth, which shall ennoble the enjoyment of 



