Page:The Development of Navies During the Last Half-Century.djvu/282

 employed quadruple-expansion engines, with a boiler pressure of 200 lbs., in a boat for the Argentine Government, with the happiest results.

It has been stated that 'No. 80' was supplied with triple-expansion engines, but she was not the first vessel to be so fitted. Here it may be well to mention that whereas in simple engines the whole process of expansion of the steam is carried out in one cylinder, and in compound engines in two, in triple-expansion engines the steam passes through three cylinders, diminishing in pressure at each step before it reaches the condenser. More work is thus got out of the steam for the same expenditure of fuel, and consequently what is known as the 'coal endurance' of ships is considerably increased.

In September 1886 was launched the 'Rattlesnake,' built and engined by Messrs Laird, of Birkenhead, the forerunner of a type of vessel considered by many good judges to be of even more importance in modern naval warfare than the torpedo boats. That the authorities themselves are of this opinion may be seen by the fact that at the present moment there are twenty-two of these vessels, now known as 'sharp-shooters,' either completed or in progress. 'In engining these ships the paramount object has been to reduce all weights to a minimum consistent with efficiency,' and in no similar instance has praiseworthy intention been so carried to an extreme as nearly to approach a crime. The propelling machinery of the 'Rattlesnake,' consisting of two sets of vertical triple-expansion three-crank engines, of 2700 horse power at 310 revolutions,