142 REPORT— 1869. 



which I reported to the British Association of 18G7. For instance, the mean 

 value of C, the unit of working strength for these bars, is 7-494 tons, whereas 

 this value for the other bars was only 5-746 tons, showing that these bars 

 are -3 stronger. The value of u, or the work of deflection for unity of 

 section, for these bars is 90-970, whereas for the other steel bars it is only 

 51-696. This value of u exhibits the powers of the several bars to resist a 

 force analogous to that of impact. It is therefore clearly shown that this 

 steel must be peculiarly well adapted to resist the force of sudden shocks, 

 considering that it is | superior in this quality to any other of the steel bars 

 before experimented upon. 



The flexibility of this steel is slightly inferior to that of other steel ; the 

 measure of flexibility (DJ being for these bars -001345, and for the other 

 bars -001361. The modulus of elasticity is somewhat low for steel, although 

 at the same time it is very little below the general average of those from my 

 former experiments. 



This steel, I consider, well adapted to withstand severe transverse strains, 

 for it combines the two essential qualities of great strength and superior 

 powers in its resistance to the force of impact. 



The mean breaking tensile strain, per square inch of section, of this steel is 

 45-28 tons ; whereas this value for the other steel bars, before experimented 

 upon, is 41-77 tons. The Heaton bars are, therefore, -08 stronger in their 

 resistance to the force of tension than the average result obtained from 

 the steel bars previously experimented upon. This result, whilst placing 

 the Heaton steel in a highly satisfactory position when compared with the 

 mean of the whole of the steel experimented upon, places it at the same 

 time below that produced by some individual manufacturers. The elongation 

 of these bars was considerable, and a good deal above the mean for the other 

 bars, thereby giving a large value for the work done in breaking the bar. 



These bars show high powers of resistance to a compressive strain, 

 aU the specimens having undergone the test of 100 tons on the square inch 

 without any visible external signs of fractiire. 



It would be very difficult to compare the diff"erent bars in their resistance 

 to compression, for nearly all the specimens underwent a strain of above 100 

 tons on the square inch without exhibiting the slightest trace of a crack. 

 As the lever by which the specimens were crushed was not competent to 

 produce a greater strain, it was impossible to find out the crushing weight ; be- 

 sides, even then, supposing it possible to produce the requisite strain, it would 

 be a task of extreme difficulty to find out at what precise weight the column 

 began to give way. Under these circumstances, it can only be left to the 

 judgment of the person wishing to select steel to resist a compressive force 

 to choose that which he thinks best adapted to his purpose, the choice being 

 regulated by the ductility of the metal as exhibited by the amount of compres- 

 sion. In looking through the experiments, however, one thing is clear, that 

 the hardest steels sustained very little compression, whilst the softer ones, in 

 the majority of cases, were reduced to almost half their original height. 



From this abstract it will be seen that this steel, manufactured by Mr. 

 Heaton, stands in the most favourable light in comparison with steel pro- 

 duced by other manufacturers ; and if it be taken into consideration that 

 two-thirds of the iron from which this steel was converted, was composed of 

 Northamptonshire pig-iron, we may reasonably look forward to this invention 

 creating a considerable improvement in the j)roductiou and cost of steel. 



Comparison of Wrour/ht Iron with Steel. 

 Having lately had occasion to experiment on some wrought- iron bars, of 



