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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