EXPERIMENTS ON CURRENTS* $ \ 



the barge, arriving first within the sterling heads, shot away 

 fro til the wherry about L'OO yards, by the superior momen- 

 tum she acquired in the increased declivity. 



A pressure perpendicular to the horizon applied to a body Perpendicular 



floating 011 a horizontal surface acts as increase of Weight, a:)cl obuc i ue 



~ pri ssure actins 



having the effect only of making the body to which it is ap- c n a floating ° 



plied swim deeper, or occupy more space in the water. An °'"- x y- 



oblique pressure, not strong enough to submerge the body, 



affects it in two directions ; one downwards in the manner 



of weight, to which the body yields to a certain and 



nite extent; the other horizontal, in which direction the body 



continually gives way to the pressure. Almost every person 



has experienced the readiness of a boat to glide from under 



him, on putting his first foot in her. These two effects of 



an inclined pressure are separately in proportion to the 



whole pressure, one as the sine, the other as the cosine, of 



the angle of incidence is to radius. 



If to a body floating on a horizontal surface a pressure is Applied to a 

 applied in a direction making with the horizon an angle of bar S e on lhs 

 89° 59', the proportion of the pressure which would act ho- 

 rizontally is to the whole pressure, as the sine of 1' is to 

 radius. And this proportion is t-uIou.tt ot> the whole pres- 

 sure. In like manner, if the surface inclines l' from the 

 true horizontal level, weight applied to a body floating on 

 that surface will give an impulse towards the declining part 

 of the surface equal to riHMftftr of the weight applied. Con-* 

 sequently, a barge having in her 100 tons weight, floating 

 with the stream where the declivity of the surface is l', will 

 receive an impulse towards the declining part of the surface 

 equal to neatly Gslbs. which is little short of what is esti- 

 mated to be the average pull of a horse. 



Hence it seems naturally to follow, that two pieces of fndication f 

 wood, equal in size but differing in weight, being placed in the course and 

 the water near to each other, would show if there was a cur- SUen £ th °* a 

 rent, by the heavier wood separating from the lighter in the 

 direction of the stream. Likewise, that the quantity of se- 

 paration in a given time might afford a measure for the 

 strength of the current. And it is probable, that this would 

 be found true in a smooth and equal running stream, where 

 110 interruption was caused by the wind* 



E 2 I gup- 



