ARTILLERY 



231 



chamber. The firing of the guns was in every respect the same. Nos. 1 and 2 

 were fired the same number of times with similar charges. No. 1 burst at tho 

 27th fire, and No. 2 at the 25th. It appears from these results, that no material 

 effect is produced on the quality of tho iron by these different modes of cooling tho 

 castings. 



A very extensive series of experiments was made, by the order of the United 

 States' Government, on the strength of guns cast solid or hollow. In these it was con- 

 firmed that the guns cast hollow endured a much more severe strain than those cast 

 solid. Considerable differences were also observed, whether the casting was cooled 

 from within or without ; and Lieutenant Hodman's method of cooling from the interior 

 is regarded as tending to prevent injurious strains in cooling. 



Major Wade informs us that time and repose have a surprising effect in removing 

 strains caused by the unequal coolings of iron castings. 



Great advances have been made in improving the quality of iron guns. Guns 

 cast prior to 1841 had a density of 7'148, with a tenacity of 23,638. Guns cast in 

 1851 had a density of 7'289, with a tenacity of 37,774. 



The following Table gives tho results of all the trials mado for the United States 

 Government, showing the various qualities of different metals : 



The following analyses of the metal of iron guns of three qualities are important:* 

 Influence of Single Ingredients. 



Influence of Two or more Ingredients. 



