VIII NOTES BY THE EDITOR. 



of nations. It seems most likely that the fuel of the future will be 

 either liquid or pulverized, and not solid, according as it is used 

 for domestic and steam-generating or for metallurgic purposes. 



The proper material for steam-boilers has been much discussed 

 by practical men during the past year, some advocating the return 

 to the original material of cast iron, and others maintaining the 

 superior advantages of steel. No boiler can be made strong 

 enough to resist the explosive power of steam under high pressure, 

 and the greater the strength of the containing chamber the more 

 destructive will be the explosion if rupture takes place. The 

 strength of a boiler being the strength of its weakest part, it is 

 impossible, taking into consideration poorness of material, un- 

 skilful workmanship, and the numerous hidden sources of weak- 

 ness in riveted wrought-iron boilers, to determine the actual con- 

 dition of such a boiler as to strength. Cast iron is better adapted 

 to undergo the ordeal of fire and water than is wrought iron, and 

 in proper shape and proportions may be made as strong. The 

 feeling of safety under high pressures has led to a general adop- 

 tion of cast-iron boilers, as this material under improper treat- 

 ment breaks at once without straining, unlike the destructive 

 fracture, of wrought iron, consequent on its very tenacity ; the 

 brittleness of cast iron, at first sight a defect, is the very element 

 of its safety. In such boilers there is no weakening by rivets, 

 and very little corrosion, apd a free and rapid circulation is 

 effected. Should a steel boiler explode, the effects would be 

 destructive in proportion to its strength. 



In naval warfare the struggle for superiority between cannon 

 and armor plates at present seems to be settled in favor of the 

 cannon, especially of the smooth-bore American heavy ordnance. 

 The American system of large bore and spherical shot is acknowl- 

 edged in " Engineering" to be superior to the English system of 

 small bores and elongated shot. The American system uses cast- 

 iron guns, which the comparatively low initial pressure allows to be 

 employed with safety ; it is, however, applicable to wrought-iron 

 guns, which places before us a large field for increased power, 

 while the English wrought-iron gun has already reached the high- 

 est efficacy compatible with the material. Recent trials at Shoe- 

 burvness have shown that the large American smooth-bore can 



V O 



send its 4401b. round shot through any armor-plate in the British 

 navy.. Twenty-inch guns have also been made, and no doubt 

 their efficacy will prove superior to the resistance of any armor- 

 plate which can be made available. 



