Easton and Amos, who procured for me twenty -two solid pillars, each 

 10 feet long and 2| inches diameter, cast out of eleven kinds of iron 

 (nine simple irons and two mixtures). The pillars were all from the 

 same model, and were cast vertically in dry sand, and turned flat at 

 the ends, as the hollow ones had been ; two being cast from the same 

 kind of iron in each case. The simple unmixed irons tried were as 

 below, and all of No. 1. 



Mean breaking weight. 



Old Park iron Stourbridge 29'50 tons. 



Derwent iron Durham 28'03 



Portland iron Tovine, Scotland .... 2 7' 30 



Calder iron Lanarkshire 27'09 



Level iron Staffordshire 24-67 



Coltness iron Edinburgh 23-52 



Carron iron Stirlingshire 23' 52 



Blaenavon iron South Wales 22'05 



Old Hill iron . . Staffordshire 20-05 



The mean strength of the pillars from the irons above varies from 

 20-05 to 29-50 tons ; or as 2 to 3 nearly. 



The pillars formed of mixed irons were found to be weaker than 

 the three strongest of the unmixed series. 



From many experiments, it was shown that the weight which 

 would crush the pillars, if they were very short, would vary as 5 to 9 



The pillars in general were broken of four different lengths, 10 feet, 

 7 feet 6 inches, 6 feet 3 inches, and 5 feet, the ends of all being turned 

 flat, and perpendicular to the axis. It was found that when the 

 length was the same, the strength varied as the 3*5 power of the 

 diameter ; and when the diameter was the same and the length varied, 

 the strength was inversely as the 1'63 power of the length. Both 

 of these were obtained from the mean results of many experiments. 



The formula for the strength of a solid pillar would therefore be 



where w is the breaking weight, rfthe diameter in inches, I the length 



