PLANE AND CONCAVE MIRRORS. 57 



Nor was it merely the low and cunning priest 

 who thus sought to extort money and respect 

 from the most ignorant of his flock : bishops and 

 pontiffs themselves wielded the magician's wand 

 over the diadem of kings and emperors, and, by 

 the pretended exhibition of supernatural power, 

 made the mightiest potentates of Europe tremble 

 upon their thrones. It was the light of science 

 alone which dispelled this moral and intellectual 

 darkness, and it is entirely in consequence of its 

 wide diffusion that we live in times when 

 sovereigns seek to reign only through the affec- 

 tions of their people, and when the minister of 

 religion aks no other reverence but that which 

 is inspired by the sanctity of his office and the 

 purity of his character. 



It was fortunate for the human race that the 

 scanty knowledge of former ages afforded so few 

 elements of deception. What a tremendous 

 engine would have been worked against our 

 species by the varied and powerful machinery of 

 modern science ! Man would still have worn 

 the shackles which it forged, and his noble spirit 

 would still have groaned beneath its fatal pressure. 



There can be little doubt that the most common, 

 as well as the most successful, impositions of the 

 ancients were of an optical nature, and were 

 practised by means of plane and concave mirrors. 

 It has been clearly shown by various writers that 

 the ancients made use of mirrors of steel, silver, 

 and a composition of copper and tin, like those 

 now used for reflecting specula. It is also very 

 probable, from a passage in Pliny, that glass 

 mirrors were made at Sidon ; but it is evident, 

 that, unless the object presented to them was 



