122 PROCEEDINGS OP THE AMERICAN ACADEMY 



TABLE XII. 

 Core, Norway Iron. — Diaphragm Steel, No. 30, Tempered. 



Strength of Induced Strength of Induced 



Field. Current. Field. Current. 



.007 6.2 .272 36.7 



.023 8.0 .302 34.8 



.070 17.3 .340 33.0 



.103 23.0 .392 29.7 



.121 26.4 .458 26.3 



.139 30.1 .538 23.2 



.157 32.8 .566 23.0 



.176 35.0 .647 21.7 



.202 37.1 .773 19.8 



.224 ... 1.046 17.6 



.246 37.0 



TABLE XIII. 

 Core, Norway Iron. — Diaphragm, Steel, No. 30, Untempered. 



Strength of Induced Strength of Induced 



Field. Current. Field. Current. 



.005 5.2 .331 31.2 



.031 11.7 .376 28.9 



.082 24.2 .437 26.0 



.103 29.7 .512 23.3 



.130 37.7 .632 20.4 



.160 41.9 .735 19.7 



.200 38.3 .819 18.0 



.231 36.2 .956 16.3 



.272 35.2 



Curve 2, Figure 1, represents the results when two of the ordinary 

 ferrotype diaphragms were superposed, forming a diaphragm of double 

 thickness, and Curve 3 of the same figure shows the results when three 

 such diaphragms were superposed. Each diaphragm was 0.01 of an 

 inch thick. The curves of Figure 2, marked 21, 22, 23, respectively, 

 show the results of similar experiments with diaphragms of sheet iron 

 whose thickness was 0.030, 0.027, 0.024 of an inch, respectively (Nos. 

 21, 22, 23, B. W. G.). Figure 3 shows the results when a steel dia- 

 phragm 0.017 of an inch thick (No. 2G) was used, the curve U being 

 that for untempered steel, and T that for tempered steel. Steel dia- 

 phragms respectively 0.026 and 0.012 of an inch thick (Nos. 22 

 and 30) gave similar results, as will be seen from Tables XL, XII., 

 and XIII. 



