EXPERIMENTS ON CURRENTS. £J$ 



middle, at small and nearly equal intervals, followed each 

 other through. That which first came to the increased fall 

 under the arch, being precipitated, left the others far be- 

 hind, till in their turn they were in like manner precipitated. 

 When they arrived out of the rapid part of the stream into 

 the smooth water, 1 did not observe, that their relative po- 

 sition was altered from what it had been before they came 

 to the bridge: but the small boat had made use of oars. 



It would answer other purposes than that of curiosity, to Altitude of th* 

 ascertain and form tables of the declivity of the surface at beSviththfe 

 different velocities of current. The observations of alti- tide, 

 fades at sea must be affected by currents, one part of the 

 sensible horizon being higher than the other. A ship sta- 

 tioned in a tide which runs one way North, the other 

 South, may expect to find the observed latitude vary with 

 the tide. 



In the afternoon of the same day that we made the expe- Attempt to as- 



riraent with the sticks (the 27th), we made a very imperfect c f rtain thede- 



i i i- • V n clivity of the 



attempt to discover what was the declivity of the surface surface of the 



above Westminster bridge, or rather what angle the plane ^ hames * 



of the surface on the flood made with it on the ebb, by 



marking at two distant stations at the same times, the height 



of the water during the flowing, and likewise during the 



ebbing of the tide. One station was at one of the posts 



close under the Speaker's garden: the other, on the same 



side of the river, at the ferry opposite Cumberland Gardens. 



The distance between the stations, according to the maps of 



London, is seven furlongs. 



At the post near the Speaker's garden, the difference of 

 the height of the river, taken at 4 P. M., the tide then flow- 

 ing, and at 7 P- M., the tide ebbing, was 25*5 inches. 



At the ferry opposite Cumberland Gardens, the difference 

 of the heights taken at the times above mentioned was 17*3 

 inches. 



The tide was lower at 7 o'clock than at 4. The stream 

 at each of those times was running at a rate which we con- 

 jectured to be nearly three miles per hour: therefore a 

 greater variation was expected than 8; 2 inches, which in u 

 distance of 7 furlongs will give only 30" for the angular dif- 

 ference between the plane of the surface on the flood, and 



the 



