244 Eon. C. A. Parsons [Jan. 26, 



opening the regulating valve on coming to the measured mile, but 

 were maintained for many miles together with constant steam pressure, 

 and as long as the fires were clean. On the other hand, the endurance 

 of the engines themselves seems to be unlimited, all heavy pressures, 

 including the thrust of the propellers, that would inordinary engines 

 come on the ben rings, being counterbalanced by the steam pressure 

 acting on the turbines. 



It seems clear that the results obtained in the case of the Turbinia 

 were almost entirely due to the economy in steam of the turbine 

 engines, and the unusually small weight of the engines, shafting 

 and propellers, in proportion to the power developed. 



It may also be said that generally speaking every part of the 

 machinery was as substantial as in naval vessels of the torpedo-boat 

 class, yet she developed 100 horse-power per ton of machinery, and 

 50 horse-power per ton of total weight of vessel in working order. 



The results of the Turbinia having been found satisfactory, the 

 original company which built her was merged into a large company 

 under the same directorate for carrying on the work on a commercial 

 scale. At Wallsend-on-Tjne, the Parsons Marine Steam Tmbine 

 Company erected works, and in 1898 contracted with the Admiralty 

 for a 31-knot torpedo-boat destroyer, the Viper (Fig. 2), which is of 

 the same dimensions as the usual 30-knot vessels of this class, viz. 

 210 feet length, 21 feet beam, and about 350 tons displacement, but 

 with machinery of much greater power than usual in vessels of this 

 size ; they also contracted with Sir W. G. Armstrong, "Whitworth and 

 Co. for machinery for one of their torpedo-boat destroyers. 



The turbine engines of these vessels are similar to those of the 

 Turbinia, but are in duplicate, and consist of two distinct sets of 

 engines on each side of the vessel. There are four screw shafts in 

 all, entirely independent of each other, the two on each side being 

 driven by one high and one low-pressure turbine respectively of about 

 equal power ; the two low-pressure turbines drive the two inner shafts, 

 and to each a small reversing turbine is also permanently coupled, and 

 revolves idly with them when going ahead. The screw shafts are 

 carried by brackets as usual, and two propellers are placed on each 

 shaft, the foremost in each case having a slightly lesser pitch than the 

 after one. The thrust from the screw shafts is entirely balanced by 

 the steam acting on the turbines, so that there is extremely little 

 friction. 



The boilers, auxiliary machinery and condensers are of the usual 

 type in such vessels, but their size is somewhat increased to meet the 

 much larger horse-power to be developed, and to compensate for the 

 lesser weight of the main engines, shafting, propellers, as well as the 

 lighter structure of the engine beds. Tlie boilers are of the Yarrow 

 type, with a total heating surface of 15,000 square feet, and grate 

 surface of 272 square feet, and the condensers have a cooling surface 

 of 8000 square feet. The hull and all fittings are of the usual 

 design. 



