4-18 Mr. Ewart on the Reaction of. effluent Water, 



recede from the perpendicular in the opposite direction to the 

 jet. — I have made some experiments on a vessel suspended in 

 that manner ; and in order to ascertain the reaction as accu- 

 rately as possible, I made use of a balance-beam furnished 

 with a perpendicular arm of the same length as the horizontal 

 arms, as represented at fig. 1. The scales were exactly ba- 

 lanced, and the end of the rod D made just to touch the side 

 of the vessel. — The orifice was then opened, and the water in 

 the vessel was kept uniformly at the same height by a stream 

 falling gently on the plate E. The scale F having been raised 

 by the reaction of the jet, weights were put into it till it was 

 brought exactly to the position in which it was before the ori- 

 fice was opened. The diameter of the vessel was 7 inches, 

 and the height BC exactly 3 feet. I tried orifices of various 

 diameters from # 35 to *7 of an inch. Their exact diameters 

 were ascertained by a micrometer, and the time carefully ob- 

 served in which 30 lbs. of water were discharged through each 

 orifice. 



When the orifice was made in a thin plate (^th of an inch in 

 thickness), I found the reaction to be greater than that stated in 

 Sir Isaac Newton's first conclusion, in the ratio of 1*14 to 1. 

 There was some variation in the results of the experiments. 

 The greatest reaction, however, was as 1*16 to 1, and the least 

 as 1'09 to 1, which fall far short of Sir Isaac Newton's last in- 

 ference. The velocity of the water at the orifice (ascertained 

 by observing the time in which 30 lbs. were discharged) was 

 less than that which a body would acquire in falling freely 

 from B to C, in the ratio of '6 to 1. 



I found no constant ratio to subsist between the diameter 

 of the contracted vein and that of the orifice ; and observing 

 considerable opacity in the jet at the contracted vein, I con- 

 cluded it to be divided into a number of different filaments, 

 and I gave up all hopes of ascertaining the actual area of the 

 section of the stream at that place by measuring its diame- 

 ter. After repeated trials I found that when the water issued 

 through a contracted hole, of the shape represented at G, the 

 jet was quite transparent, and the reaction (taking the mean of 

 12 experiments with 4 different orifices) was less than the 

 weight of a column of water of twice the height of the head 

 and diameter of the smallest part of the hole, in the ratio of 

 •865 to 1. The least reaction was as '85 to 1, and the greatest 

 as *88 to 1. By measuring the quantity of water delivered in 

 a given time, I found the velocity of the jet, at the smallest 

 part of the orifice, to be less than that which a body would 

 acquire in falling freely from B to C, in the ratio of '94 to 1. 

 The highest ratio was as '95 to 1, and the lowest '89 to 1. 



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