PRIME-MOVERS. 357 



An extremely useful feature in engines of this kind, is their adapta- 

 bility to be driven by the pressure of water derived from an ordinary 

 water works, and in this manner small manufacturers carrying on 

 business in their own houses are enabled to obtain a prime-mover 

 with great ease and all things considered at small cost ; and not only 

 is advantage taken of such machines for the purpose of driving manu- 

 factories, but water cylinders are now largely used for working the 

 bellows of church organs, for which purpose, however, an overshot 

 water-wheel is shown as being employed as far back as Salomon de 

 Caus's book, date 1615. 



Large water-wheels or even water-engines are comparatively costly 

 machines, and as large water-wheels make but few revolutions per 

 minute they require expensive and heavy gearing to get up speed, and 

 thus it is that it frequently becomes a desirable thing to dispense with 

 such machines and to resort to other modes of making available high 

 falls of water. In former times this was done by suffering the im- 

 petuous stream of water to beat upon the pallets of water-wheels, but 

 from such machines only a poor effect could be obtained, as a large 

 portion of the energy in the water was devoted to the formation of 

 eddies and the generation of heat and to the production of lateral 

 currents, leaving but a small percentage available as motive power. 



Much of the evil effect, however, attendant upon using the impact of 

 water as a means of driving water-wheels is obviated by the con- 

 struction invented by the distinguished French engineer Poncelet. 

 For high falls, however, the implement now generally employed is 

 the turbine, of which the well-known Barker's Mill may be looked 

 upon as the germ. 



I have got before me No. 1983, a model of Fourneyron's turbine. 



This is not an apt model for my present purposes, inasmuch as it 

 represents a turbine to be employed with a comparatively low fall of 

 water; but even in such instances the turbine gives most excellent 

 results, and it has the advantage over the water-wheel of being capable 

 of working with great efficiency, although there may be a considerable 

 rise in the "tail-water," a rise which would materially check the 

 action of an ordinary water-wheel. In this turbine every care has 

 been bestowed to give a proper form to the pallets on which the 

 water acts, so as to take up step by step, as it were, the whole of the 



