392 THE INTELLECTUAL RISE IN ELECTRICITY. 



A few words of preface may be granted, because von 

 Guericke has ideas of his own about these virtues, which, 

 together with life and matter, enter into the constitution 

 of all bodies. They are effluvia sometimes corporeal, 

 such as the air sometimes incorporeal, or more properly 

 highly diffused, such as those which emanate from a body, 

 and surrounding it, form its orb or sphere of virtue. Of 

 the incorporeal virtues there are many not all percepti- 

 ble, because of defects in our senses; but those which we 

 are best able to recognize come from the earth or from the 

 sun. Thus from the earth arise "impulsive virtue," "di- 

 rective virtue," "turning virtue," "sounding virtue," 

 and soon; while the sun yields "light and coloring vir- 

 tue," and the moon "frost-making virtue." Then there 

 are other virtues derived from the planets, which the 

 astrologers call "influences." 



All of these virtues are alike in that they can act at a 

 distance. They join themselves to neighboring bodies, 

 which simultaneously recognize them; but if any virtue 

 meets a body not suited to it, it is repelled or reflected, 

 and the repercussions may continue until the virtue is ex- 

 hausted and ceases. The more solid the body, the more 

 virtue it is capable of receiving. Certain virtues accord 

 with certain bodies and there is mutual suitability. They 

 are excited therein by attrition, collision, touch, vibration, 

 and so on. 



Von Guericke's "impulsive virtue," so called, appears 

 to be simply momentum. "Conservative virtue" is grav- 

 ity. "Directing virtue" is Gilbert's verticity, the mag- 

 netic force which he thought adjusted the earth's axis in 

 space and prevented its nutation. "Turning virtue" is 

 any impressed rotary motion; von Guericke gives as an 

 example a man revolving on his heel. "Sounding vir- 

 tue" is that which causes the sensation of sound, and is 

 produced "by the friction of bodies." "Heating virtue" 

 is heat due to subterranean fire or "friction of the sun's 

 virtue." " Lighting virtue" is the sensation of light and 



