NOVUM ORGANUM 419 



considerable depth, in order to see whether the clock move more 

 quickly from the increased power of the weights. But if this 

 power be found to diminish at a height, and to increase in sub- 

 terraneous places, the attraction of the corporeal mass of the 

 earth may be taken as the cause of weight. 



Again, let the required nature be the polarity of the steel 

 needle when touched with the magnet. We have these two ways 

 with regard to this nature: Either the touch of the magnet 

 must communicate polarity to the steel towards the north and 

 south, or else it may only excite and prepare it, whilst the actual 

 motion is occasioned by the presence of the earth, which Gilbert 

 considers to be the case, and endeavors to prove with so much 

 labor. The particulars he has inquired into with such ingeni- 

 ous zeal amount to this: I. An iron bolt placed for a long 

 time towards the north and south acquires polarity from this 

 habit, without the touch of the magnet, as if the earth itself 

 operating but weakly from its distance ( for the surface or outer 

 crust of the earth does not, in his opinion, possess the magnetic 

 power), yet, by long-continued motion, could supply the place 

 of the magnet, excite the iron, and convert and change it when 

 excited. 2. Iron, at a red or white heat, when quenched in a 

 direction parallel to the north and south, also acquires polarity 

 without the touch of the magnet, as if the parts of iron being 

 put in motion by ignition, and afterwards recovering themselves, 

 were, at the moment of being quenched, more susceptible and 

 sensitive of the power emanating from the earth, than at other 

 times, and therefore as it were excited. But these points, though 

 well observed, do not completely prove his assertion. 



An instance of the cross on this point might be as follows : 

 Let a small magnetic globe be taken, and its poles marked, and 

 placed towards the east and west, not towards the north and 

 south, and let it continue thus. Then let an untouched needle 

 be placed over it, and suffered to remain so for six or seven 

 days. Now, the needle (for this is not disputed), whilst it re- 

 mains over the magnet, will leave the poles of the world and 

 turn to those of the magnet, and therefore, as long as it remains 

 in the above position, will turn to the east and west. But if the 

 needle, when removed from the magnet and placed upon a 

 pivot, be found immediately to turn to the north and south, or 

 even by degrees to return thither, then the presence of the earth 

 must be considered as the cause, but if it remains turned as at 

 first, towards the east and west, or lose its polarity, then that 

 cause must be suspected, and further inquiry made. 



Again, let the required nature be the corporeal substance of 

 the moon, whether it be rare, fiery, and aerial (as most of the 

 ancient philosophers have thought), or solid and dense (as Gil- 

 bert and many of the moderns, with some of the ancients, hold). 



