662 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



a certain combination of nearly the same dimensions as Y of Figure 13, 

 which was tested in a solenoid for which 47rw/10 was very nearly 

 equal to 25. The first column in Table VIII. gives the intensities of 

 the exciting currents used, the second and third columns the fluxes 

 after the currents had been suddenly interrupted. 



L in Figure 1 7 represents a combination of two coaxial shells and a 

 core, very accurately made and carefully annealed by Mr. Thompson. 

 The diameters, in centimeters, of the five cylindrical surfaces were 1.12, 

 1.58, 2.53, 3.00, 3.96. This system was treated like all the other test 

 pieces and the fluxes through all three members were determined after 

 the currents which had been slowly applied had been slowly brought to 

 zero and again after they had been suddenly destroyed. Tables IX. 

 and X. give the remanent fluxes for the slow breaks and for the quick 

 breaks respectively. I represents the solenoid current in amperes. 



The signs are nearly all difi'erent according as the current is slowly 

 or quickly destroyed. 



The observations already described represent fairly all our 'work 

 upon combinations of solid shells and cores and it remains to mention 

 the special case represented by the nearly straight line of Figure 14. 

 Here the shell was of the same dimensions and of similar material as 

 that used in the work which led to the curve LMNZ in the same 

 figure, but this shell was slit through lengthwise by a single saw cut 

 which prevented currents from circulating around it. Many of our 



