504 



Mr. S. J. Lochner on the Elongation 

 Table VI. 



I. 



II. 



III. 



IV. 



1 



018 



6-8 



17750 



2 



0-26 



9-8 



19420 



3 



0-33 



124 



20890 



4 



0-42 



15-8 



22160 



5 



0-53 



20-0 



25390 



6 



0-67 



25-3 



27220 



7 



105 



39-6 



29610 



7-2 



1-65 



62-2 



31960 



62 



2-63 



101-0 



34250 



5-2 



3-43 



129-3 



34880 



4-2 



4-05 



152-7 



36300 



3-2 



4-70 



1772 



36580 



2-2 



5-60 



211-1 



37240 



1-2 



633 



238-6 



37960 



Backward 









maximum. 









7'8 



0-92 



34-7 



28800 



In order to determine the effect of the thickness of his bar 

 upon the amount of expansion, Mr. Bidwell selects for the 

 purpose three rods of 100 millim. length and 2'65, 3*65, and 

 6*25 millim. in diameter. He assumes that the iron in the 

 three bars may be regarded as similar, and that the differences 

 in the expansion are due only to their diameters. He finds 

 that the expansion " varies inversely as the square root of the 

 diameter " (the length remaining the same). I regret to say 

 that my results do not in any way confirm his conclusions. 

 Instead of finding that larger bars give less expansion than 

 smaller bars, I find just the opposite. 



At first I thought that the best way to make this test 

 would be to take my largest bar and turn it down to suc- 

 cessively smaller diameters. In fact, I did this with bar I. 

 The resultant bar, which I have called No. VI., showed a 

 falling off of the expansion from 10'3 fringes to 7*2 fringes. 

 I found it a very difficult matter to turn so long a bar per- 

 fectly true in the lathe which I had at my disposal ; and at 

 the same time I was not certain about the effect of the strains 

 due to the turning. Further, there was no certainty that the 

 inside of my bar would behave in the same manner as the 

 outside. 



Taking into consideration these factors, I determined that 

 the most feasible method of avoiding the difficulties would be 



