EXCEPTIONAL PHENOMENA. 311 



proceeded to test with great care the other assertion in- 

 volved, they would have become still better convinced 

 of the truth of their own theory. A stone dropped from 

 the top of a high tower, or into a deep well, would 

 certainly not have been deflected from the vertical direc- 

 tion in the considerable degree required to support the 

 anti-Copernican views ; but, with very accurate obser- 

 vation, they might have discovered, as Benzenberg sub- 

 sequently did, a very small deflection towards the west 

 (vol. i. p. 453). At the moment when a body begins to 

 fall freely, it begins to resemble a very small satellite 

 moving under the force of gravity, as exerted from the 

 earth's centre of attraction, and it therefore describes, like 

 other satellites, a portion of an elliptic orbit b . Had the 

 Copernicans then been able to detect and interpret the 

 meaning of this small divergence, they would have found 

 in it a conclusive proof of their own views. 



Multitudes of cases might be cited in which laws of 

 nature seem to be evidently broken, but in which the 

 apparent breach entirely arises from a misapprehension of 

 the facts of the case. It is a general law, absolutely true 

 of all crystals yet submitted to examination, that no 

 crystal has a re-entrant angle, that is an angle which 

 towards the axis of the crystal is greater than two right 

 angles. Wherever the faces of a crystal meet they pro- 

 duce a projecting edge, and wherever edges meet they 

 produce a corner. Many crystals, however, when care- 

 lessly examined, present exceptions to this law, but closer 

 observation always shows that the apparently re-entrant 

 angle really arises from the oblique union of two distinct 

 crystals. Other crystals seem to possess faces contradict- 

 ing all the principles of crystallography ; but again 

 careful examination shows that the supposed faces are not 



b 'Cambridge and Dublin Mathematical Journal' (1848), vol. iii. 

 p. 206. 



