100 Prof. Magnus's Hydraulic Researches. 



of cohesion, contracts, that is, becomes thicker and narrower, it 

 brings the rays nearer together. It is, however, manifest that 

 by this mutual approximation the thinner is far more deviated 

 from its direction than the thicker, because a greater quantity of 

 motion is present in the latter. Hence results the pecuhar form 

 of the edge df. 



33. Between the form of the surface which fig. 11 represents 

 and that represented by fig. 1.2, occur all possible variations, 

 according as both jets intersect more or less centrally. Besides 

 this, the forms of the surfaces are changed, as much by an alter- 

 ation in the relative diameters of the jets as by the change in the 

 angle at which they meet, or in the distance of the place of con- 

 tact from the oiitlet. But all these forms may be explained in 

 a similar manner to §§ 30 and 31. 



Experiments with Jets ivhich issue under different pressures. 



33. It has been assumed in the preceding, that both jets 

 issued at the same pressure. By narrowing one of the caout- 

 chouc tubes in the apparatus described in § 4 the pressure could 

 be regulated, as thereby the afilux was lessened. 



Savart has described the action of jets which move towards 

 each other in the same line imder different pressures*, hence the 

 present treatise will be confined to jets which meet at an angle. 

 If both issue from equal circular orifices, a water surface is 

 formed as in the case already described ; this does not, however, 

 bisect the angle formed by the two jets, but follows more the 

 direction of that which moves with the greater velocity. The 

 surface is also not plane, but concave on the side of the jet with 

 the greater velocity. 



34. Since the surface follows the direction of the resultant of 

 both jets, § 17, it is manifest that it does not bisect the angle of 

 the jets. The reason that it appears concave is as follows : — Let 

 us suppose that both jets are divided into strata of equal thick- 

 ness, which are parallel to the axes, and at right angles to the 

 plane going through both axes. Then the corresponding strata 

 of both jets, which lie on the interior side of the angle, meet 

 sooner than the rest. The interior strata have therefore already 

 formed a surface before the next strata encounter. But the 

 place in which the succeeding strata encounter is evidently not 

 in the surface resulting from the preceding strata, but more 

 towards the side of the surface having the smaller velocity. Hence 

 the middle of the surface already formed would be pressed towards 

 this place. This process is repeated for all successive strata, and 



* Annales de Chmie et de Physique, 2nd series, vol. Iv. p. 257. 



