MancJiestcr McDioirs, Vol. Iv. (191 1), No. 13. 3 



the bend, and indicate further that the loss of energy in 

 the bend itself is no greater, but on the contrary is some- 

 what less, than the loss in the same length of straight 

 pipe.* This indicates that the stability is increased by 

 changing straight line motion into motion in a curved 

 path, with the velocitj' greatest at the inside of the curve. 



In view of the apparent discrepancy between the 

 conclusions to be drawn from these results, and those 

 commonly accepted, further experiments, somewhat on 

 the lines originally adopted, have been carried out by the 

 author. In the first of these a cylindrical drum, 4 inches 

 in diameter and 12 inches long, is mounted so as to be 

 capable of rotation about a vertical axis fixed centrally in 

 a cylindrical vessel 12 inches in diameter and 12 inches 

 high. The drum being in position the vessel is filled with 

 water. When this has come to rest a colour band is 

 introduced radially across the space between the drum 

 and the vessel, after which the drum is rotated slowly. 

 The colour band shows that the water gradually takes up 

 the motion, the streak being gradually wound into a 

 spiral thread without any trace of eddy formation. When 

 rotation is stopped the water in contact with the drum is 

 brought to rest, and eddies are formed breaking up the 

 spiral for a certain distance towards the outside of the 

 vessel. The phenomena are therefore identical, whether, 

 as in Reynolds' experiment, the outer layers, or, as in 

 the present experiment, the inner layers, are originally 

 rotating the faster. 



In the second experiment, the same drum was mounted 

 with its axis vertical and central, over an orifice pierced 

 in the bottom of a cylindrical vessel 2 feet in diameter. 

 Water is supplied to the latter through a volute, opening 



* BrightiiKjre. I'roc. Inst. Civil Eni^hieeis, vol. 169, 1906-7, pt. iii., 

 P- 334. 



