46 PROCEEDINGS OF THE AMERICAN ACADEMY 



to the range short of the absolute strength of the explosive material 

 used. It is the strength of the gun which not only gives the range, 

 but makes rifling possible, with precision and all the advantages of the 

 elongated shot. All inventions relating to the different modes of rifling, 

 the form of the projectile, and the devices for breech-loading, are 

 necessarily subordinate to the question of strength ; with this sufficient, 

 those become simple problems, to be rapidly determined by the ingenu- 

 ity of many inventors. 



Now the limit of strength of cast-iron and of bronze cannon had long 

 ago been reached. Excepting Captain Rodman's improvement, and 

 certain modern advantages in working and casting metals, no material 

 advantages had been gained over guns cast in the reign of Queen 

 Elizabeth. 



But' the most effective guns of the present day embody new prin- 

 ciples of strength. They are all built-up guns. With them are associ- 

 ated the names of Armstrong, Blakely, Whitworth, Parrott, and others. 

 Whatever may be the relative merits of these several varieties, our 

 interest is confined to the question of their strength, that is, to the prin- 

 ciples of construction which have made them stronger than common 

 guns, and rendered their respective subordinate improvements possible. 

 These principles are two, and their introduction at different times 

 into the manufacture of cannon constitutes two successive steps, and 

 the only steps, which give distinctive character to the guns under con- 

 sideration. Both originated with Mr. Treadwell. 



These two inventions are often confounded, although more than ten 

 years elapsed between them. The confusion is doubtless owing in 

 some degree to the fact that the two are found combined in nearly all 

 the modern built-up guns. The first initiated a system of construction 

 which may be designated as the coil system ; the second, what may be 

 named the hoop system. 



The first was successfully applied to the making of cannon by Mr. 

 Treadwell in the year 1842, and a full account of it was published in 

 1845 ; the gist of the invention being in so. constructing the gun that 

 the fibres of the material shall be directed around the axis of the 

 calibre. 



This method of construction is described .in Professor Tread well's 

 own language as follows: "Between the years 1841 and 1845 I made 

 upwards of twenty cannon of this material [wrought iron]. They 

 were all made up of rings, or short hollow cylinders, welded together 





