BOOK II. J INSTANCES OF THE CROSS. all 



crust of the earth docs not, in liis opinion, possess the majjnetic 

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

 magnet, excite the iron, and convert and chantjje 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 ob- 

 served, do not completely prove his assertion. 



An instance of liie 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 suHercd to remain so for six or seven days. 

 Now, the needle (for this is not disputed), whilst it remains over 

 the magnet, will leave the poles of the w orld 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 consi- 

 dered as the cause, but if it remains turned as at first, towards 

 the east and west, or lose its polarity, then that cause must bo 

 Buspected, and farther inquiry made. 



Again, let the required nature be the corporeal substance of 

 the moon, whether it be rare, liery, 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).** 

 The reasons for this latter opinion are grounded chiefly upon 

 this, that the moon reflects the sun's rays, and that light does 

 not appear capable of being reflected except by solids. The 

 instances of the cross will therefore (if any) be such as to ex- 

 hibit reflection by a rare bod}^ such as flame, if it be but sufli- 

 ciently dense. !Now, certainly, one of the reasons of twilight is 

 the reflection' of the rays of the sun by the upper part of the 

 atmosphere. We see the sun's rays also reflected on fine even- 

 ings by streaks of moist clouds, with a splendour not less, but 



^ Bacon plainly, from this passage, was inclined to believe that the 

 moon, like the comets, was nothing more than illuminated vapour. The 

 Newtonian law, however, has not only established its solidity, but its 

 density and weight. A sufficient proof of the former is afforded by 

 the attraction of the sea, and the moon's motion round the earth. Ed. 



' Rather the refraction, the sky or air, however, reflects the bVj« 

 jays of light. 



