Reproduced by courtesy of Messrs. F. Davidson & Co. 



A PIECE OF HIGH-SPEED STEEL SEEN UNDER THE 

 HIGH MAGNIFICATION OF I,5<X> DIAMETERS 



Note the marked lines of flow. 





Photo: J. J. Ward. 



SCALE FROM A GOLD-FISH 



Showing the rings of growth by which the age of the fish can be 

 reckoned. Starting from a little speck, the scale has line upon line 

 added to it. Periods of rapid growth alternate with periods of slow 

 growth ; or the growth in summer may be different in character from 

 the growth in winter; and thus alternate zones are established. Just 

 as we can tell the age of a tree by counting the summer and autumn 

 rings on the cut stem, so, after getting some secure data, we can 

 tell the age of the fish. It keep its diary on its scales. 



