548 



PROFESSOR KNOTT ON THE STRAINS PRODUCED IN 



But, excepting that the rate of fall-off is on the whole greater in these cases, the in- 

 duction does not in its variation follow the variation of the field along the tube. For 

 example, with the combination 020, the change of field between the successive positions 

 is very nearly the same. On the other hand, the induction, in its manner of variation 

 from section to section, follows much the same law as in the other combinations just 

 named. 



Iron Tube VII. 



Coil Combination. 



040 



10201 



2002 



020 



1001 



100001 



Amp. 



2-68 



1-35 



•57 



3-97 



2-01 



•84 



3-99 

 1-99 



•84 



3-97 



2-03 



•85 



3-83 

 1-64 



•77 



3-90 

 1-64 



•84 



3-87 

 1-64 



•84 



7480 

 6730 

 5210 



7820 

 7120 

 6110 



7710 

 6910 

 5560 



6180 

 5540 

 3110 



7670 

 6250 

 4540 



5750 

 4510 

 2440 



2460 

 995 

 468 



Amp. 



B, 



2-66 



1-35 



•56 



3-90 



2-01 



•84 



3-94 



2-01 



•84 



3-94 



2-03 

 •84 



3-82 

 1-65 



•77 



3-90 

 1-66 



•77 



3-86 



1-64 



•85 



7260 

 6440 

 4520 



7620 

 6760 

 5430 



6860 

 5910 

 4320 



6920 

 5940 

 3290 



6230 

 5370 

 3780 



6420 

 5390 

 2740 



2520 



1040 



499 



Amp. 



B, 



2-66 

 1-31 



•54 



3-90 



1-99 



•80 



3-86 



1-98 



•79 



3-88 



1-99 



•80 



3-77 

 1-63 



•77 



3-8 

 1-65 



•78 



3-79 

 1-63 



•78 



3700 

 2780 

 1790 



3590 



2820 

 1970 



3080 

 2280 

 1470 



4100 

 3080 

 1720 



1890 

 1500 

 1070 



3360 

 2350 

 1280 



1940 



872 

 425 



Again, the field due to combination 2002 is, broadly speaking, an inversion of the 

 field due to 020, being smallest at the centre and greatest near the ends. The induction 

 in this case is somewhat smaller at the centre than at the intermediate section, but falls 

 off markedly towards the ends. In these cases of rapid variation of field, the induction 

 does not vary nearly so rapidly. Indeed, the most uniform distributions of induction 

 are obtained with combinations 2002, 1001, and 100001, which give three of the least 

 uniform distributions of field. 



We now pass to the consideration of the volume changes of certain tubes when 

 subjected to these several distributions of field. In the following tables the volume 

 changes are given in the same unit as formerly — 10" 5 cubic centimetre. Each column 

 is headed by the symbol of the coil combination ; and in the first column of all are 

 entered the currents in amperes to which the volume changes correspond. These, as in 



