142 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



oscillograph records; all the testing instruments were different in the 

 two cases, and no comparison was possible until the final results were 



TENTHS OF SECONDS. 



Figure 34. 



Theoretical forms of current curves in a coil of 1394 turns belonging to the 

 magnet Q. In practice these would be somewhat modified by eddy currents. 



B' 



obtained and were found to differ 

 from each other by onl}^ one part 

 in about fourteen hundred. The 

 labor of reducing the oscillograms 

 I was very great, and this extremely 

 close agreement must be consid- 

 ered accidental, since it is not 

 easy to make a large mass of iron 

 go over exactly the same magnetic 

 journey twice. 



Hysteresis diagrams for the 



magnet Q and corresponding to 



maximum excitations of 1812, 



5370, and 10,880 ampere turns 



are given in Figure 36. Some 



results of measurements of the 



Tlie horizontal rod AB is threaded ^^^ changes in the core for the 



and the brass masses C,X> can be screwed ,. . c ,-, ■, 



on the rod as far as is necessary. The ^^'^t of these cycles are given m 



system must be accurately b.alanced. I able 111 



W 



T 



Figure 35. 



