HOW THE SHADOW MAY BE MADE TO MOVE 

 BACKWARD ON THE SUN-DIAL 



|N the twentieth chapter of II Kings, at the 

 eleventh verse we read, that " Isaiah the prophet 

 cried unto the Lord, and he brought the shadow 

 ten degrees backward, by which it had gone 

 down in the dial of Ahaz." 



It is a curious fact, first pointed out by Nonez, the 

 famous cosmographer and mathematician of the sixteenth 

 century, but not generally known, that by tilting a sun-dial 

 through the proper angle, the shadow at certain periods of 

 the year can be made, for a short time, to move backwards 

 on the dial. This was used by the French encyclopaedists 

 as a rationalistic explanation of the miracle which is related 

 at the opening of this article. 



The reader who is curious in such matters will find direc- 

 tions for constructing "a dial, for any latitude, on which 

 the shadow shall retrograde or move backwards," in 

 Ozanam's " Recreations in Science and Natural Philosophy," 

 Riddle's edition, page 5 29. Professor Ball in his " Mathe- 

 matical Recreations," page 214, gives a very clear explana- 

 tion of the phenomenon. The subject is somewhat too 

 technical for these pages. 



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