Page:The Development of Navies During the Last Half-Century.djvu/333

 but should the Howell exhibit decided improvement it may eventually take the other's place.

Compressed air is a convenient force, and for propelling a projectile has the great advantage of not varying in its action. Two charges of gunpowder of equal weight may, from variation in manufacture, or a slight difference in moisture, or climatic influence, throw two projectiles in succession from the same gun to widely distant spots. The atmosphere when compressed is not subject to such influences or variations, and has a less violent action than gunpowder. These characteristics have led to its employment to propel large charges of high explosive from a long tube, more commonly known as the dynamite gun. This originated in America, where a successful application of the principle has led to the construction of a small vessel called the ’Vesuvius' with three of these guns, from which 500 lbs. of dynamite or gun cotton can be thrown to the distance of a mile with great accuracy. The velocity being low, considerable elevation has to be given, as in mortar fire, and hence against a moving object a successful shot is most uncertain. But against an object whose position does not alter, when the range is ascertained, great destruction could be accomplished with such projectiles.

In the armament of their new fleet the United States has been able to commence at a period when the experience of other nations in breech-loading rifled guns can be utilised. But plant and machinery for construction had to be provided as well as the heavy steel forgings from which the modern gun is made. Under the energetic