St 



EXPERIMENTS ON CURRENTS. 



Experiments 

 with sti 

 sacisfadl 

 than before. 



Long poles re- 

 quisite at cea. 



Experiment 

 with heavy 

 ■wood a foot 

 beneath the 

 surface. 



the plane on the ebb ; so that the angle of declivity from 

 the horizontal level, supposing it equal each way, was not 

 more than 15". Perhaps the difference would have been 

 found greater, if the marks had been taken in mid stream, 

 id of close 1<> the side of the river. The stoppage of 

 WtestiriifiBte'r-bridge msty likewise be supposed to occasion 

 some swell in the part of the liver immediately above it, dur- 

 ing tiie ebb tide. 



On Wednesday, August the 3d, we again made experi- 

 ments with sticks; which proved less satisfactory than those 

 we had before made. But, previous to describing farther 

 operations, it is necessary to notice a consideration, which, 

 when it first occurred, seemed an insurmountable objection 

 to deriving any benefit from them. This was, the great dif- 

 ference between the surface in a river, and the surface m an 

 open sea; so that an experiment, which might be found to 

 succeed in the one, might scarcely be at all practicable in 

 the other. To this objection it is reasonable to answer, or 

 at least a reasonable encouragement to expect, that if a 

 small stick will point the direction of the stream in a river, 

 a lont; pole (a steering sail boom, for instance), will, in cir- 

 cumstances tolerably favourable, do so at sea. It seems 

 within the rule of just proportion, that a spar as large as a 

 steering sail boom as much exceeds a walking stick, as the 

 irregularity of the surface at sea, in temperate weather, 

 exceeds that of a river, in the experiment; two or more 

 might be put into the sea at the tame time, and if they 

 agreed, there would be the greater reason for placing reliance 

 on the result. 



Our next trial was with one of the South Sea island clubs, 

 of a wood not buoyant, about three feet in length, and gra- 

 dually tapering. It was buoyed at each end with cork, but 

 with string enough to let it be about a loot under the sur- 

 face ; and that the corks at. each end might be equally ex- 

 posed to the air, they were so managed as to show equally 

 and similarly above water. There is reason, however, to 

 think it would have been more proper to have allowed the 

 exposure to the air at each end to be proportioned to the 

 weight sustained. In the manner the experiment was made, 

 the club, being left to itself in the stream, did not take or 



keep 



