IQ BULLETIN 173, U. S. NATIOxN'AL MUSEUM 



at the ends (but provided with orifices) extending from the vertical 

 tube. When the vertical tube was filled with water, the water escaped 

 through orifices in the arms in tangential jets, which by their reaction 

 caused the tube to rotate. This simple turbine had a maximum 

 efficiency of about 66 percent. Its principal defect was the require- 

 ment of a vertical tube of a height equal to the head of water, con- 

 taining a mass of water that was rotated as so much useless weight. 

 This design was improved by curving the horizontal arms, and many 

 such turbines, known as Scotch mills, were put in use. The number 

 of arms was gradually increased until the turbine took the form of a 

 complete wheel. In 1826-27 Benoit Fourneyron constructed a tur- 

 bine in which stationary guide vanes at the center of the wheel 

 directed water into vanes in the rim of the wheel. This was the first 

 radial outward-flow turbine. The next turbine (1841) was that of 

 Nicolas Jonval. This was an axial-flow turbine in which the water 

 moved parallel to the shaft. It consisted of a horizontal wheel with 

 vanes set radially in the rim. A ring of stationary guide vanes above 

 the rotor directed the water against the moving vanes. In 1826 

 Poncelet proposed an inward-flow turbine the opposite of the 

 Fourneyron. 



American developments in icater wheels. — Water mills were among 

 the first permanent structures built by the early settlers in the Amer- 

 ican colonies. As early as 1646 Massachusetts granted a patent to 

 Joseph Jenks, an iron worker, "for making the engines for mills to 

 go by water," an indication that water mills were in use some time 

 before this. By 1700 every settlement had its mills employed in a 

 great variety of work, grinding grain, rags, plaster, malt, chocolate, 

 and tobacco; breaking leather; fulling cloth; boring gun barrels; slit- 

 ting iron; and sawing wood. Many relics of these old mills remain 

 in every part of the original colonies, some in a state of more or less 

 complete preservation. 



Though the mills on the Delaware and the Chesapeake prior to the 

 Revolution were considered the equal of any in the world, their ex- 

 cellence was due to the flexibility and completeness of their gearing 

 rather than to the efficiency of their water wheels. Practically all 

 the American mills used the undershot wheels, which were capable 

 of converting only a small fraction of the power of the streams. 

 After the Revolution the great water powers of the New England 

 and Middle Atlantic States were extensively developed, and very com- 

 plete systems of dams, reservoirs, and canals were constructed to per- 

 mit the recovery of every possible bit of energy from the streams. 

 In most of these mills the wooden pitchback wheel, which turned 

 inward to the fall, was used. The water struck just short of its 

 highest point, the power being produced by the weight of the water, 

 which was retained in the buckets until it reached the bottom by a 



