732 



SCIENTIFIC RECREATIONS. 



are two kinds of magic squares, some formed by terms of arithmetical pro- 

 gression, others by terms of geometrical progression. We must also 

 distinguish the equal from the unequal magic squares. 



Fig. 860. The sixteen puzzle. 



We give here several examples of magic squares with terms of 

 mathematical progression, among them the square of 34, giving one of the 



Fig. 861. The numbers placed at hazard, and No. 16 removed. 



solutions to the puzzle just described (fig. 862). We also give an example 

 of a magic square composed of terms of geometrical progression. The 

 double progression for examples I, 2, 4, 8, 16, 32, 64, 128, 256, as here 



