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



issues tangentially from the bent pipes, and by the reaction causes 

 the sphere to rotate. 



It seems uncertain whether this machine was ever more than a 

 toy, or whether it was used by the Greek priests for producing motion 

 of apparatus in their temple ; but from our experience within the 

 last twenty years it appears that, with some improvements in design 

 and construction, it could have been applied to perform useful work 

 at the date of Hero, and further that, when so improved, it might have 

 claimed a place among economical steam engines, even up to the 

 middle of the present century. 



A few years ago I had an engine constructed to test the capabili- 

 ties of this class of reaction steam turbine, the only difference be- 

 tween this engine and Hero's being that the sphere was abolished, 

 as a useless incumbrance, the arms were made of thin steel tube of 

 oval form, so as to offer the least resistance to their motion, and the 

 whole was enclosed in a cast-iron case which was connected to a 

 condenser. When supplied with steam at a pressure of 100 lbs. per 

 square inch, and a vacuum in the case of 27" of mercury, a speed of 

 5000 revolutions per minute was attained, and an effective power 

 was realised of 20 horse, and the consumption of steam was only 

 40 lbs. per brake horse-power. By this very creditable performance, 

 I was encouraged to further test the system, and constructed a com- 

 pound reaction engine, in which the steam was caused to pass succes- 

 sively through three pairs of arms on one hollow shaft, each pair 

 being contained in a separate compartment through which the shaft 

 passed, suitable metallic packing preventing the passage of steam 

 from one compartment to the next. The performance of this engine 

 wag, however, not superior to that of the single two-arm Hero's 

 engine, for the simple reason that the excessive resistance to motion 

 of the arms in the denser steam of the compartments more than 

 neutralised the gain from the compound form. The performance of this 

 engine was, however, sufficiently good to have it placed on a par with 

 many ordinary steam engines in the middle of the present century. 



The great barrier to the introduction of Hero's engine was un- 

 doubtedly the excessive speed of revolution necessary to obtain 

 economical results, and with the crude state of mechanical engineer- 

 ing at that time, it would have been a matter of some difficulty to 

 construct the turbine engine with sufficient accuracy of workmanship 

 for satisfactory results, to say nothing of the necessary gearing for 

 applying the power to ordinary useful purposes. 



The next steam engine mentioned in history, which is capable 

 of practical and useful development, is Bianca's in 1629. It is of 

 the simplest form, a jet of steam from a steam boiler impinges on a 

 paddle-wheel and blows it round. This form of engine has since 

 1889 been developed by Dr. Ue Laval, of Stockholm, with great 

 ingenuity, and is extensively used for moderate powers on the 

 Continent. The speed is, however, necessarily very high in order 

 to obtain economy in steam, and spiral reduction gearing is used in 



