310 THE INTELLECTUAL RISE IN ELECTRICITY. 



a conception which, emanating from a mind of the six- 

 teenth century, is an inspiration and a marvel, v 



Then he says that if the attracted body were moved by 

 an air-current, it would remain in contact with the electric 

 but for a moment. On the contrary, that this attractive 

 power persists "sometimes for as long as five minutes, 

 especially if the weather is fair." Such is the first state- 

 ment of the electric charge. 



That the amber does not attract the air, but the body, is 

 shown by its drawing the particles on the surface of a drop 

 of water into a cone, and not moving the whole drop. But 

 this landed him in another paradox; for how could the 

 electric thus attract water if, as he had already found, 

 water directly applied to the electric destroyed its attract- 

 ive power? So he concludes that it is one thing to sup- 

 press the effluvium at its rise, and another to destroy it 

 after it is emitted. Hence, he discovers that to cut off the 

 attraction completely it is necessary not merely to inter- 

 pose a silk texture midway between the electric and the 

 object, but quickly to lay it over the electric directly after 

 friction. This is the first suggestion of insulation applied 

 directly to the charged conductor the prototype of the 

 coating which covers the wires which convey the currents 

 through our streets and dwellings, and prevents leakage 

 of them on the one hand while guarding us from their 

 dangers on the other. 



While Gilbert's experiments often end in genuine dis- 

 coveries, and involve conceptions far in advance of his 

 time, it not infrequently happens that his deductions and 

 conclusions are vague, speculative and obscure. This not 

 onlyoccurs when (as he says himself in his preface), after 

 having described his magnetic experiments and accounted 

 for the homogenic parts of the globe, he turns to the gen- 

 eral nature of the whole earth, and then proceeds u to 

 philosophize freely, r> but even in his statements as to what 

 his experiments specifically prove. His notion of electric 

 effluvia finds its true limit when he describes the emana- 



