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VIII. On the Mechanical Stretching of Liquids: an Experimental Determination of 
the Volume-Extensibility of Ethyl-Alcohol. 
By A. M. Worthington, M.A., Professor of Physics and Head Master of the 
Royal Naval Engineering School, Devonport. 
Communicated by Professor Poynttng, F.R.S. 
Received February 1,—Read February 4, 1892. 
[Plate 10.] 
Three methods are known by which a liquid may be subjected to a bodily tension. 
(1) The method of the inverted barometer, familiar to most physicists, by which, 
with care, a mercury column of many times the barometric height may be supported 
by its adhesion to the top of the tube. In such a column the hydrostatic pressure is 
negative above the barometric height, or the liquid above this level is in a state of 
tension. This tension increases with the height and is propagated in all directions 
to the walls of the tube. When the upper part of the tube is made elliptical in cross- 
section and of thin glass, its yielding to the inward pull may be easily observed. 
(2) The centrifuged method, devised by Professor Osborne Reynolds, in which a 
U-tube, ABCD, of glass, closed at both ends, contains air-free liquid, ABC, and 
vapour, CD. This tube is fixed to a suitable board and whirled about an axis, C, a 
little beyond the end, A, and perpendicular to the plane of the board. If CE (see 
figure) be the arc of a circle described about 0, then while rotation continues the 
B 
liquid between E and A is in a state of tension, increasing from zero (if we ignore the 
vapour-pressure) at E to a maximum at A. By this method Professor Osborne 
Reynolds has subjected water to a tension of about 5 atmospheres or 72'5 pounds 
per square inch, while the author, experimenting in the Cavendish Laboratory in 
2 z 2 20-7.92. 
