442 



FOURTH REPORT 1834. 



Experiments made on Water, August 9th, 1834. 



The results were, 1st, That when the artificial river or re- 

 cipient was exactly level, it required two streams of equal 

 magnitude to raise the main stream to double of its original 

 height: 2ndly, That when the artificial river or recipient was 

 set at angles of inclination of from 1 to 10 degrees, a sensible 

 diminution took place in the altitude of the main stream, as 

 well as in the ratio of increase in the tributaries, corroborating 

 in some degree the experiments of Gennete. 



In addition to the Italian collection, there appeared, at dif- 

 ferent intervals, a variety of works on the motions of rivers by 

 Mariotte, Hermanns, Michelini, Michelotti, Fontana, Poleni, 

 Statlerius, Ximenes, &c. In the year 1779 tlie Italian collection 

 was first made known in this country by the Abbe Mann, in a 

 valuable Treatise on Rivers and Canals, in the Philosophical 

 Transactions. The author recapitulates the different doctrines, 

 propounded by Torricelli and others, on the motions of rivers, 

 from the laws of their action, to the establishment of their beds. 

 He adopts the principles of Guglielmini in almost every instance 

 relative to the accelerations and retardations of rivers, and shows, 

 according to the principles laid do^vn by Leibnitz and Euler, 

 that, in order to render the velocity of a current everywhere 

 equal, the bed should have the form of a curve, along which a 

 moving body should recede from a given point, and describe 

 spaces everywhere proportionate to the times. 



