£$ EXPERIMENTS ON CURRENTS. 



The above paper was read at a meeting of the Royal So- 

 cle; , February l6th, 1809. In consequence of some obser- 

 vations which it produced, the following remarks, in addition, 

 were presented, and read at the Society. 

 Weight impels In a paper I had the honour to present to the Hoyal So- 

 thes:ream it- c ' ie ty, on the progress made by some bodies floating in a 

 the'body float- stream, they descending faster than the stream itself, 1 en- 

 ing «nit. deavoured to show, that this progress was the effect of per- 

 pendicular pressure, producing impulse towards the declin- 

 ing part of the surface. The same cause, indeed, evidently 

 applies to the production of the stream itself; consequently 

 the surface, and whatsoever floats on it, are, in this respect, 

 on an equal footing, and the whole agree in pressing for- 

 ward and in opposing resistance to whatsoever endeavours 

 to overtake them. Without some auxiliary caxise, therefore, 

 a floating body cannot overtake the stream. 

 Shape and di- The different shapes of bodies, and likewise the directions 



rection of a j n wn ich they are placed with respect to the direction of the 



body afreets its . ... r 



velocity. impelling power, expose them to more or less resistance. A 



barge floating crossways to the stream receives the progres- 

 sive impulse with the least advantage, her whole length act- 

 ing in resistance to her overtaking the stream. The same 

 barge when endways with the stream, is acted upon by the 

 same quantity of impelling power, and her progress is op- 

 posed by less resistance. 

 Weight adds With increase of weight, both the impelling power and 

 impulse than ***« res * stance are increased : but when the barge is length- 

 to the resist ways with the line of the stream, weight added will increase 

 ance. ^he impelling power in a greater proportion than the resist- 



ance is increased. Hence the heavy barge in a calm will 

 overtake the light barge. 



This short explanation I beg to offer as an addition to my 

 former remarks on the subject, and shall be glad if it assists 

 in any satisfactory manner to accouut for vessels overtaking 

 the stream in a calm. 



May 15th, 1809. 



X. 



