148 LETTERS ON NATURAL MAGIC. 



magician as but an ordinary man, who borrows 

 from the sciences the best working implements 

 of his art. But when, in the midst of solitude, 

 and in situations where the mind is undisturbed 

 by sublunary cares, we see our own image 

 delineated in the air, and mimicking in gigantic 

 perspective the tiny movements of humanity ; 

 when we see troops in military array performing 

 their evolutions on the very face of an almost 

 inaccessible precipice when, in the eye of day, 

 a mountain seems to become transparent, and 

 exhibits on one side of it a castle which we know 

 to exist only on the other ; when distant objects, 

 concealed by the roundness of the earth, and 

 beyond the cognisance of the telescope, are 

 actually transferred over the intervening convexity 

 and presented in distinct and magnified outline to 

 our accurate examination; when such variec" 

 and striking phantasms are seen also by all arounu 

 us, and therefore appear in the character of real 

 phenomena of nature, our impressions of super- 

 natural agency can only be removed by a distinct 

 and satisfactory knowledge of the causes which 

 gave them birth. 



It is only within the last forty years that 

 science has brought these atmospherical spectres 

 within the circle of her dominion ; and not only 

 are all their phenomena susceptible of distinct 

 explanation, but we can even reproduce them on 

 a small scale with the simplest elements of our 

 optical apparatus. 



In order to convey a general idea of the causes 

 of these phenomena, let ABC D, Fig. 35, be a 

 glass trough filled with water, and let a small 

 ship be placed at S. An eye situated about E, 



