164 | Account of Experiments made 
1780, in his elaborate investigation of the forms of columns, 
Mr. Coulomb had however shown before that time, how inap- 
plicable all these calculations were to columns under common 
circumstances ; and you, sir, have repeated the observation in 
your lectures on natural philosophy. The results of experiments 
have also been equally discordant ; since it is deduced from those 
of Reynolds, that the power required to crush a cubic quarter of 
an inch of cast iron is 448000!bs. avoirdupoise, or 200 tons; 
whereas by the average of thirteen experiments made by me on 
cubes of the same size, the amount never exceeded 10392°53 lbs. 
not quite five tons*, This may be seen by referring to the tables. 
There were four kinds of iron used, viz. ist. Iron taken from the 
centre of a large block, whose crystals were similar in appear- 
ance and magnitude to those evinced in the fracture of what is 
usually termed gun-metal. 2dly. Iron taken from a small cast- 
ing, close grained, and of a dull gray colour. 3dly. Iron cast 
horizontally in bars of 2th inches square, § inches long. 4thly. 
Iron cast vertically, same size as last. These castings were re- 
duced equally on every side to { of an inch square: thus re- 
moving the hard external coat usually surrounding metal castings. 
They were all subjected toa gauge. The bars were then pre- 
sumed to be tolerably uniform. ‘The weights used were of the 
best kind that could be procured, and as the experiment ad- 
vanced, smaller weights were used. 
Experiments on Cast-Iron in Cubes of % of an Inch, Se. 
Iron taken from the block whose specific gravity was 7:033. 
Averages. lbs. avuirdupoise. 
ix om By it .. ‘ 1454 
1439662 4x1 uf yes 22 ek a 
axt ye al i3 ae 1449 
i) 
On specimen 
n 
oO 
different lengths. Specific gravity of iron aes 
192 
t xe 4p ap Hi Hes 
baer ene th i obi 
1x 2 slipped with 1863Ibs. filed flat, and 
crushed with ap we 2363 
ix ditto, 1495, ditto iy 2005 
1758°5 < x ditto, “fh Hs 4 1407 
ix ditto, A ate m 1743 
1x2 ditto, ais ys pis 1594 
Li x4 ditto, os A oy 1439 
* It is probable that Mr. Reynolds made his experiments or metal cast 
at the furnace of Maidley Wood, which is of a very strong and superior 
quality: but this circumstance can have been but of little importance com- 
pared to the great disproportion of the results, 7 
April 
