IRON, STEEL, AND NICKEL TUBES IN THE MAGNETIC FIELD. 



549 



former cases, are all taken from the curves which were plotted from the observations of 

 experiment. 









Volume Changes. 















Combinations of Coils. 







Current in 

 Amperes, 































6 



040 



10201 



2002 



020 



1001 



100001 









Iron VII. 









•2 



- 1-9 



- 1-8 



- -6 



- -6 



- -2 



- -1 





•4 



- 5-8 



- 6 



- 2-6 



- 2-6 



- -8 



- -4 



1 



•6 



+ 4 



+ 1-4 



- 4-5 



- 5-4 



- 1-8 



- 1 





•8 



+ 14-6 



+ 12 



+ -8 



- 1-7 



- 3-2 



- 2-8 



o 

 T3 



1-0 



+ 19-6 



+ 17-5 



+ 8'3 



+ 4-1 



- 4 



- 4-3 



ts m 



1-25 



+ 22-2 



+ 20-9 



+ 12-2 



+ 9-2 



- 2-7 



- 5-1 





1-5 



+ 23-7 



+ 22-8 



+ 14-5 



+ 11-8 



+ 6-6 



- 2-4 



is ® 



2-0 



+ 25-6 



+ 24-7 



+ 17-5 



+ 14-5 



+ 19-2 



+ 13-3 



a 



2-5 



+ 26-9 



+ 25-9 



+ 19-5 



+ 16-4 



+ 24-2 



+ 20-9 





3-0 



+ 27-6 



+ 26-7 



+ 20-7 



+ 17-8 



+ 27-3 



+ 24-7 





4-0 





+ 27-5 



+ 22-7 



+ 19-6 



+ 30-6 



+ 28-8 



> 









Nickel VII. 









•2 



+ 4 



+ 4 



+ 2 



+ 1 



+ 1 



+ 1 



+ 



•4 



- 22 



- 17 



- 2 



+ 4 



+ 4 



+ 3 



+ 



•6 



- 67 



- 58 



- 21 



- 11 



- 2 



+ 2 



+ 



•8 



-113 



-103 



- 50 



- 37 



- 18 



- 4 



+ 1 



1-0 



-149 



-134 



- 74 



- 60 



- 40 



- 18 



+ 1 



1-25 



-180 



-160 



-100 



- 81 



- 69 



- 41 



+ 2 



1-5 



-199 



-178 



-121 



- 97 



- 96 



- 64 



+ 2 



2-0 



-218 



-202 



-151 



-118 



-140 



-102 



- 2 



2-5 



-228 



-213 



-171 



-134 



-166 



-132 



- 6 



3-0 



-234 



-220 



-186 



-145 



-181 



-152 



- 8 



4-0 





-226 



-204 



-155 



-204 



-184 



- 11 



The first thing to be remarked here is the general resemblance throughout the 

 successive columns for each metal. The field in which the volume change alters sign 

 gradually rises as we pass from combination to combination. 



Confining our attention to the higher fields, we see that there is a steady diminu- 

 tion of effect with any given current as we pass in succession from one to another of 

 the first four combinations. This quite agrees with what we should expect to be the 

 case, at all events for the first three combinations. For — see the Table of Inductions — 

 these three combinations give rise to distributions of induction of the same type, but of 

 diminishing average value. For the fourth combination (2002) the distribution of in- 

 duction changes type somewhat, but there is only a very slight fall of the average in- 

 ductions as compared with the preceding combination (10201). The diminished volume 

 changes are, especially in the case of nickel, too large to be explained merely in terms 

 of the diminution in the average value of the induction. Now, we have just seen that 

 the combination 2002 gives greater uniformity of magnetisation along the tube than do 

 the others. Thus we seem to have an experimental proof of what is highly probable on 

 theoretic grounds, that the variable distribution of induction along the tube has an im- 



