308 THE INTELLECTUAL RISE IN ELECTRICITY. 



the thing attracted mutually come together by a movement 

 of coition. This effused Form (field of force) is wholly in- 

 corporeal. It is the animating energy, or as Thales looked 

 upon it, the "soul" of the magnet. 1 



The attraction of the electric, however, he concludes to 

 be due to a diametrically-opposite cause. The force is not 

 awakened until the substance is rubbed, and then the sub- 

 stance is altered that is to say, it attains a moderate heat, 

 becomes shining or polished, and finally gives out an ef- 

 fluvium. This effluvium is corporeal it is the original 

 Matter in another condition like a vapor that is given off 

 from a fluid, or as if the body were dissolved into an ex- 

 halation. 



Now as to the qualities of this effluvium, he says that 

 the effect of moist breath, or a current of humid, atmos- 

 pheric air, or a sheet of paper, or a linen cloth, interposed 

 between the electric and the object attracted, is to choke its 

 powers. Thus the electric differs entirely from the magnet, 

 which attracts through any obstacle. Barriers such as the 

 foregoing therefore act physically to stop the progress of 

 the material electric effluvium, while they are perfectly 

 transparent to the immaterial, effused, magnetic Form. In 

 order to produce this effluvium, the heat generated in the 

 body itself, not heat contributed by other bodies, must act; 

 and a gentle and rapid friction must be used, not force 

 applied violently and recklessly, to cause the finest efflu- 

 vium to arise from a subtle solution of moisture an ex- 

 ceedingly attenuated humor, much more rarefied than the 

 ambient air. To explain how such a humor could be ob- 

 tained from so dense a body as the diamond, he instances 

 odoriferous substances which exhale fragrance for cen- 

 turies; having in mind, perhaps, the still-persistent odor 



1 See Spectator, No. 56, May 4, 1711, for this same comparison. Addi- 

 son describes Albertus Magnus as placing the lodestone on glowing coals 

 and perceiving " a certain blue vapor to arise from it which he believed 

 might be the substantial Form: that is, in our West Indian phrase, the 

 soul of the lodestone. ' ' 



