202 Mr. Dunlop’s Experiments on the Strength [Manecn, 
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BS ees 14'S 120 130 | 250 | 23 | 23 33°; 8,000 250,000 
or 170 
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aio | a 264 | 384 | 34 | 34 | 37 |11,390 356,000 
3,3 |°26 288 408 | 3 3 15,625 488,280 * 
4\3 | 23 580 | 700] 3 | 42 | 39 /20,800| 650,000 
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1) 4% | 33 1120 | 1240 | 5 yi 37 |42,875| 1339,810 * 
8 | 43 | 33 1542 1 1662) 5 | 5 | 37 1647 ,937 
9) 43) 4 1818 | 1938 | 5 8 2000,000 
10 | 43 | 44 2038 | 2158 | 6 IG | 39 2395,750 
The above are the particulars of nine experiments made in 
Cloud, Girdwood, and Co.’s Works, in 1818, with the view to 
ascertain the strength of cast-iron bars when subjected to twist 
or torsion ; and it was from the result of these experiments, taken 
as data, that the diameters of the shafts for Broomwood Mill 
were resolved upon. 
As the shafts on which the experiments were made were old 
ones and greasy, their being unsound was more easily perceived 
than if they had been new shafts. 
Having ascertained these facts, the practical use of them is 
obvious and easy; for example, if it be required to find the 
diameter of such a shaft as will require the utmost force of a 
steam-engine of any given power to break it, let m = the 
momentum of the piston; that is, the pressure of the steam 
upon it in lbs. weight, multiplied into its velocity in feet per 1’, 
and let v = the velocity of the circumference of an imaginary 
pulley supposed to be fixed upon the first shaft employed to 
communicate motion to the greatest quantity of machinery 
which the engine is calculated to drive, and suppose the radius of 
this imaginary pulley equal to the length of the lever employed 
in these experiments, and a rope coiled round this pulley, we 
* Unsound, but in a small degree. } 
' + In this experiment, the shaft having a large hole in it, broke with very little 
strain, 
