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



537 



case. Hence, on the whole, the effect is less pronounced in this kind of steel than in iron. 

 Plate III. gives the results for the steel cap ; Plate IV. for the brass cap. 



To facilitate comparisons the following tables have been prepared from the graphs. 

 As in the case of the iron, they give the changes of volume for a succession of definite 

 fields. 



Steel Tubes with Steel Cap. 





II. 



III. 



IV. 



V. 



VI. 



VII. 



25 



+ 



+ 



+ 



- -30 



- -74 



+ 



50 



+ -3 



+ -22 



+ -32 



- -62 



- 1-16 



+ 1-25 



75 



+ -85 



+ -80 



+ 1-18 



- -18 



- -80 



+ 3-4 



100 



+ 1-25 



+ 1-02 



+ 2-07 



- -22 



- -30 



+ 6 05 



125 



+ 1-1 



- -38 



+ 1-70 



-1-20 



+ -30 



+ 8-80 



150 



+ -62 



-3-12 



+ 1-87 



- -70 



+ 1-45 



+ 9-80 



200 



+ -35 



-3-03 



+ 2-69 



+ 1-17 



+ 4-20 



+ 7-60 



250 



+ -03 



-2-82 



+ 3-59 



+ 2-50 



+ 6-03 



+ 3-40 



300 



- -25 



-2-65 



+ 4-37 



+ 3-50 



+ 7-28 



- 1-40 



400 



-1-29 



-2-72 



+ 4-80 



+ 4-82 



+ 8-80 



-1L80 



500 



-335 



-301 



+ 5-10 



+ 5-03 



+ 9-90 



-20? 







Steel Tubes with Brass Cap. 







25 



+ 



- -1 



_ 



- -3 



- -7 



+ -1 



50 



+ -1 



- -35 



- -1 



-1-1 



- 1-55 



+ -6 



75 



+ -22 



- -50 



- -05 



-1-50 



- 1-90 



+ 2-5 



100 



+ -50 



- -80 



+ -19 



-1-95 



- 2-00 



+ 4-8 



125 



+ -70 



-1-80 



+ -77 



-2-80 



- 1-55 



+ 7-16 



150 



+ -70 



-2'6 



+ 1-4 



-1-9 



+ -85 



+ 8-2 



200 



+ -65 



-3-8 



+ 2-7 



+ -9 



+ 3-8 



+ 6-3 



250 



+ -55 



-2-6 



+ 3-8 



+ 2-82 



+ 5-67 



+ 3-4 



300 



+ -50 



-1-93 



+ 4-6 



+ 3-8 



+ 7-1 



- 1-4 



400 







-1-4 



+ 5-53 



+ 5-0 



+ 9-1 



-11-4 



500 



- -48 



-11 



+ 6-0 



+ 6-2 



+ 10-8 



-20-4 



It is hardly possible here to trace any well-marked law in the manner in which the 

 volume alters as we pass from tube to tube. And yet — with perhaps the exception 

 of the last two — there is an undoubted resemblance between any contiguous pair. 

 Thus Nos. II. and III. (steel-capped) both show a maximum in field 100-110. From 

 this maximum No. III. falls off abruptly to a minimum in Field 150. No. II. shows no 

 such minimum. But in other respects the graphs belong to the same type. 



In like manner there is an obvious similarity between Nos. III. and IV. ; and yet in 

 some respects No. IV. is more nearly related to No. II. For the greater part of the 

 range of field No. II. lies between Nos. III. and IV. Thus the successive transitions 

 from II. to III. and III. to IV. are totally unlike one another. Further, any attempt 

 at imagining a law of transition, if such were possible, would be hopelessly confounded 

 when No. V. came to be considered. For, except in the very highest fields, No. V. lies 

 below No. IV., just as Nos. II. and III. do. There is, however, a general resemblance 

 in form between Nos. IV. and V., although the latter has a minimum preceding the 

 maximum. This curious undulation does not appear in No. VI., which otherwise, in the 



