REPORT ON HYDRAULICS. — PART II. 



Rivers Isis and Thames. 



48T 



The velocity of the Thames might be expected to fol- 

 low the law of variation of the inclinations; but the natural 

 obstructions which exist in all parts of the river upwards, from 

 bends, shoals, islands, weeds, &c., and the artificial obstacles 

 from weirs, pound-locks, fishing-aytes, &c., render it impos- 

 sible to ascertain the velocity correctly. Much depends also 

 upon the volume of water passing down the river, and the use 

 oijla^hes. 



In general the velocity may be estimated at from half a mile 

 to two miles and three quarters per hour, but the mean velocity 

 may be reckoned at two miles per hour. In the year 1794 the 

 late Mr. Rennie found the velocity of the Thames at Windsor 

 two miles and half per hour. 



The produce of the river varies also with the situation and 

 the seasons. 



The river when gauged in a very dry season m June, 1794, 

 at Windsor, produced 961 cubic feet per second ; 

 at Laleham, .... 1153 do. 



at Kingston Bridge . 1600 do. 



According to Messrs. Rennie's experiments made on the 28th and 

 29th of May 1835, the produce was 1700 cubic feet per second; 

 and on the 29th of May, after rain . 1800 do. do. 



