144 
MINUTES OE PROCEEDINGS OF 
(46) Specimens cut out of crank-shafts are improved by additional 
hammering. 
(47) The galvanizing or tinning of iron plates produces no sensible 
effects on plates of the thickness experimented on. The results, however, 
may be different should the plates be extremely thin. 
(48) The breaking strain is materially affected by the shape of the speci¬ 
men. Thus the amount borne was much less when the diameter was 
uniform for some inches of the length than when confined to a small portion— 
a peculiarity unascertained and not even suspected. 
(49) It is necessary to know correctly the exact conditions under which 
any tests are made, before we can equitably compare results obtained from 
different quarters. 
(50) The startling discrepancy between experiments made at the Koyal 
Arsenal, and by the writer, is due to the difference in the shape of the 
respective specimens, and not to the difference in the two testing machines. 
(51) In screwed bolts the breaking strain is found to be greater when 
old dies are used in their formation than when the dies are new, owing to 
the iron becoming harder by the greater pressure required in forming the 
screw thread when the dies are old and blunt, than when new and sharp. 
(52) The strength of screw-bolts is found to be in proportion to their 
relative areas, there being only a slight difference in favour of the smaller 
compared with the larger sizes, instead of the very material difference pre¬ 
viously imagined. 
(53) Screwed bolts are not necessarily injured although strained nearly to 
their breaking point. 
(54) A great variation exists in the strength of iron bars which have 
been cut and welded; whilst some bear almost as much as the uncut bar, 
the strength of others is reduced fully a third. 
(55) The welding of steel bars, owing to their being so easily burned by 
slightly over heating, is a difficult and uncertain operation. 
(56) Iron is injured by being brought to a white or welding heat if not 
at the same time hammered or rolled. 
(57) The breaking strain is considerably less when the strain is applied 
suddenly instead of gradually, though same have imagined that the reverse 
is the case. 
(58) The contraction of area is also less when the strain is suddenly 
applied. 
(59) The breaking strain is reduced when the iron is frozen ; with the 
strain gradually applied the difference between a frozen and unfrozen bolt 
is lessened, as the iron is warmed by the drawing out of the specimen. 
