310 Mr. Mallet on the Physical Conditions 



T. The relations also of British and foreign wrought-iron have been 

 pointed out, and some popular notions of the invariable supe- 

 riority of the latter brought into question. 



8°. The principles upon which depends success in future efforts to pro- 

 cure large masses of wrought-iron, of reliable quality, have been 

 deduced from the principles ascertained as to its molecular consti- 

 tution, as determined by the mode of manufacture. 



9°. The difficulties affecting the applications of gun-metal have been 

 treated with more regard to chemical and physical science than 

 appears to have been previously done, and some suggestions offered 

 as to directions of probable improvement in the methods of alloy- 

 ing and moulding the metal ; with explanations not before given, 

 of some of the singular and obscure phenomena of its conso- 

 lidation. The most elaborate previous treatises on this subject, 

 such as those of Massas, Meyer, and Herve, left very much to be 

 desired, and much remains yet to be investigated. 



10'. The general comparison of physical, and other properties, of tlie 

 four great materials for ordnance has been finally reduced to tabu- 

 lation, and their fiscal relations compared. 



11°. The important relations of elasticity and extensibility, to ultimate 

 strength, in guns of whatever material, have been discussed, and the 

 I'esult pointed out, — that mere tenacity is not a sufficient guide ; 

 that the safe coefficient of rupture, cannot be taken at more than 

 one half that safe for static loads, since the extension for impulse 

 is double that for passive strain. 



12°. The important relations of elasticity to crystalline axis in wrought- 

 iron, developed by the application of the general law of its crys- 

 tallization, has been made the basis, in connexion with the theo- 

 retic conditions of resistance to internal pressure, for proposing 

 a better combination of wrought-iron in guns ; in principle, radi- 

 cally different from anything previously brought forward. 



13". The prevalent notions, as to the vast superiority of steel as a mate- 

 rial for ordnance, have been, it is hoped, assigned their just value. 



14'. The nature and effects of distortion by unequal temperature, in 



