THE ROYAL ARTILLERY INSTITUTION. 
141 
The conclusions drawn by Mr Kirkaldy from the results of his 
experiments are as follows:— 
(1) The breaking strain does not indicate the quality, as hitherto assumed. 
(2) A high breaking strain may be due to the iron being of superior 
quality, dense, fine, and moderately soft, or simply to its being very hard 
and unyielding. 
(3) A low breaking strain may be due to looseness and coarseness in the 
texture, or to extreme softness, although very close and fine in quality. 
(4) The contraction of area at fracture, previously overlooked, forms an 
essential element in estimating the quality of specimens. 
(5) The respective merits of various specimens can be correctly ascertained 
by comparing the breaking strain jointly with the contraction of area. 
(6) Inferior qualities show a much greater variation in the breaking strain 
than superior. 
(7) Greater differences exist between small and large bars in coarse than 
in fine varieties. 
(8) The prevailing opinion of a rough bar being stronger than a turned 
one is erroneous. 
(9) Rolled bars are slightly hardened by being forged down. 
(10) The breaking strain and contraction of area of iron plates are 
greater in the direction in which they are rolled than in a tranverse 
direction. 
(11) A very slight difference exists between specimens from the centre 
and specimens from the outside of crank-shafts. 
(12) The breaking strain and contraction of area are greater in those 
specimens cut lengthways out of crank-shafts than in those cut crossways. 
(13) The breaking strain of steel, when taken alone, gives no clue to the 
real qualities of various kinds of that metal. 
(14) The contraction of area at fracture of specimens of steel must be 
ascertained as well as in those of iron. 
(15) The breaking strain, jointly with the contraction of area, affords 
the means of comparing the peculiarities in various lots of specimens. 
(16) Some descriptions of steel are found to be very hard, and, conse¬ 
quently, suitable for some purposes; whilst others are extremely soft, and 
equally suitable for other uses. 
(17) The breaking strain and contraction of area of puddled- steel plates, 
as in iron plates, are greater in the direction in which they are rolled ; 
whereas in ca^-steel they are less. 
