yO DESCRIPTION OF A RHEUMAMETER. 



Method of ^q use it, a boat being anchored in the stream, the log 



is to be thrown into the water, and suftered to float away, 

 till the whole of the green cord alone remains on the reel, 

 which is stopped at this point by a catch. One person then 

 looking at a seconds watch gives the signal, when the second 

 hand begins its revolution, and instantly the other, who 

 holds the reel, sets loose the catch ; the log floats on, and 

 the time it takes to riin out the ten yards of line shows the 

 velocity*. 



To determine the absolute force of the current on the 

 cube, slip the loop at the end of the cord off the knob on 

 the reel, and hook it to the hole of the little dynamometer, 

 and the number of degrees shown by the index will express 

 the maximum of the action of the water on a surface of l6 

 square inches. 



This action is not constantly the same, not only from the 

 effect of the waves, but from the natural current, which 

 appears not to be always regular^ In facf: we have observed, 

 in calm weather, without any apparent waves, that the 

 force of impulse varied from one insrant to another in the 

 proportion of 6 to 8, or even more. 

 Experiments But the velocity has a great action, as will appear from a 

 ^* table of the experiments we ma«le at Paris between the 



Pont des Arts and Pont-Royal, on the 20lh of July, I8O9. 

 The weather was calm, and the Seine a little below its mean 

 height, being at 1^^ met. [4 feet 11 in,] qn the graduated 

 scale of the Pont-Royal. 



9n the Seine, ^irst situation, 10 yards from the side, opposite the wickets of 



the Louvre. 



J?xp, 



1. Veloc.insec.|25 X 



2 26^ f Force inhec^)5. : 



3 26 J 



2 tp 3 : in oz, avoird. 7 to 10^ 

 g .,......,. 26 J 



• The person who holds the reel in hh. right hand might dispense ■with 

 «n assistant, by holding in his left a stop watch, stopped at the end of the 

 revolution of the seconds hand. He would only have to set loose the 

 stop with the forefinger of the left hand, at the instant he disengaged th? 

 catch with the ri^^ht, and stop the watch again the moment the line wag 

 run off the reel. C* 



S^C0^4 



