involved in the Construction of Artillery, 



219 



Table X. 



Resist^vnt Vis Viva, of Elasticity and of Rupture by Tension of the Metals applicable to the Construction 



of Ordnance. 



Cast-steel (English), blue temper, . 



Cast-steel (German), soft, . . . 



Wrought-iron bar (maximum duc- 

 tility), 



Wrougbt-iron (mean strength and 

 ductility), 



Wrought-iron bar, strong and rigid, 



Cast-iron, mean, 



Gun-metal, cast, mean, . . . . 



Brass ivire, drawn and softened, 



Brass, cast, mean, 



■Value for 

 unit of 



lent^tli and 

 section. 



Dj-nams. 



39-650 



103-500 



96-000 



64-075 

 38-325 

 12-287 

 93-525 

 31-680 

 20-900 



Coefficient of 

 elasticity for 

 unit of section. 



42-666-750 

 28-866-725 



25-000^000 



28^444^500 



28^444^500 



17^066^700 



9^9o5-57o 



9^173^190 



8-930-000 



No. 1, From Morin's e,xperimeut3 on flexure of dj-namometric springs. 



No. 2, From Mono's and Poucelet's Tables ; but the value of r is probably greatly too high. 



No. 8, From Ardaut's experiments on line brass wire, and require to be taken with resen-e. 



1.51. On examining this Table, the importance of holding in view the value 

 of Te and Tr, rather than the mere static strain, or that from a passive load, as 

 respects the construction of artillery, becomes very striking. Thus, in the case 

 of tempered cast-steel, although the resistance to a passive strain is taken as 

 high as 21 tons per square inch, yet, from the extremely small range of exten- 

 sion, the " work done" to bring it to the limit of its safe load is found to be less 

 than that required for soft ductile wrought-iron, that will only bear a passive 

 load of about one-third as much as the steel, in the ratio of 5-175 : 7"660. So 

 also by the comparison between the soft ductile iron No. 3, and the much 

 stronger (to a passive strain), but less extensible, iron. No. 5 : the " work done" 

 in the former at the elastic limit being 7"660 : 6-955 in the latter. Again, it 

 will be remarked, that, although so much weaker, in mere tenacity, under 

 passive strain, than- wrought-iron, yet, from the far greater extensibility of cast- 

 iron (No. 5), the "work done" to bring it up to its elastic limit, is actually 

 greater than that of wrought-iron of mean quality (No. 4), in the ratio of 

 5-997 : 5-026 ; while, lastly, we may remark that gun-metal, with a tenacity 

 at the elastic limit a third under that of cast-iron, requires nearly as much 

 " work done" by a dynamic effort, to bring it to that point. 



