VON GUERICKE' s COSMICAL THEORIES. 393 



color. It is clear that von Guericke perceives that there 

 are certain resemblances between the phenomena due to 

 the play of natural forces, and has, perhaps, a hazy notion 

 of some correlation between them of the development of 

 one phenomenon from another, as the production of heat 

 by friction of the sun's virtue. Hence he is seeking, in 

 the language of the arithmetics, to reduce all these factors 

 to a common denominator. This he finds in the idea of 

 "virtues." They are all different, these natural happen- 

 ings light and sound and magnetism and heat and grav- 

 ity but none the less they are all "virtues" emanating 

 from a physical body, such as the earth or the sun, and as 

 such they are as necessary a concomitant of that body as 

 the matter whereof it is composed. 



This is von Guericke's main hypothesis, corresponding 

 to the magnetic theory of Gilbert. But he differs squarely 

 from Gilbert in the belief that the earth is a great magnet. 

 The globe, he says, is moved by the rays of the sun and 

 its own intrinsic turning virtue; by two forces, and hence 

 it would naturally be controlled unevenly. Therefore it 

 is given by nature a directive virtue (whereof its poles 

 are merely termini), "so that it does not sway this way 

 and that in its position, not even on account of the rubbing 

 of the rays of the sun, and so that it does not wabble or 

 nutate in its* own daily rotation, and change the times of 

 the year, length of days," etc. This directive virtue is 

 not inherent to the earth itself, but is imparted to it by 

 nature, which does nothing in vain, and for the express 

 purpose of preventing wabbling. Consequently he con- 

 cludes that Gilbert is wrong in regarding the globe as 

 intrinsically a big magnet. 



There is, however, still another virtue, but which is of 

 higher import than all of the others. Von Guericke goes 

 back to Aristarchus, and says that he, believing the earth 

 to be animate, revised the opinion of those who thought that 

 it had both an attractive and a repelling faculty. "This," 

 says von Guericke, "appears harmonious with reason, 



