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98 A. M. Mayer—Effects of Magnetization 
The coefficients of elongation and of retraction of seven rods of differ- 
ent species of iron, and of three steel rods of various degrees of 
hardness. 
It remains to give the determinations I have made of the co- 
efficients of elongation and of retraction. Those measures were 
made on rods of circular sections, 60°1 inches long and ‘5 inch in 
diameter. As previously stated, the iron rods were thoroughly 
annealed, and the steel rods were carefully tempered. On the 
ends of the rods, numbers were stamped, and these marks cor- 
responded to the rods as follows: 
i. Scrap Iron. 
3 ———— Ulster Tron. 
3. i 
4, English refined Iron. 
5. ow Moor Iron. 
6. Fall River Iron. 
000. Steel soft. 
00. Steel hardened and drawn to blue. 
0 Steel hardened and drawn to yellow. 
k, and immediately after recording them, I again made and 
broke the circuit and noted the two corresponding — of 
the telescope-scale. I then continued making and breaking 
the circuit and recording the scale-divisions, until the rod begat 
_to elongate from the heat produced on demagnetization. 
The tables I here present consist of six columns, A, B, C, D, 
E, and F. Under A are designated the rods; B contains the 
elongations or retractions produced on first passing the current; 
