Exp. 7. If a capillary tube, composed of two cylin ders of different bores, be immersed in a fluid first with the widest part downwards, as at E, Fig. 5. and after wards with the narrowest part downwards, as at F, Fig. 5. the fluid will ascend in both cases to the same height.
Exp. 8. When the widest part of the tube is not ca pillary, but is of such a magnitude that the fluid will not rise spontaneously to the smaller part, let the wider part be filled by suction, and the fluid will stand at the same height in the smaller part of the tube, as it would have done had the whole tube been of the same bore with the capillary part.
Exp. 9. If the tube, when filled by suction, as in the preceding experiment, is placed in the receiver of an air pump, and the air exhausted, the fluid in the wider part of the tube will not remain suspended in the tube as for merly, but will fall down into the vessel.
Exft. 10. If one tube is placed within another so that their axes coincide, the water will rise in the space be tween the tubes only to half the height that it would have done in a single tube, in which the diameter of the bore is equal to the interval between the two tubes.
Exp. 11. When the internal diameter of several ca pillary tubes are equal, the fluid will rise to the same height whether the tubes are thin or thick.
Exp. 12. Having plunged a capillary tube into wa ter, let the lower extremity of it be closed with the fin ger, and when the tube is taken out of the water, let its external surface be gently wiped. Upon withdrawing the finger, the water is seen to subside in the tube and form a drop at its lower base ; but the height of the co lumn is always greater than the elevation of the water in the tube, in the common experiment of plunging it in water. It has also been observed, that the increase in the elevation of the water is more considerable, the smaller the diameter of the drop beneath.
Exp. 13. If a drop of water is introduced into a co nical capillary tube, open at both ends, and held in a hori zontal position, it will move towards the vertex of the cone.
Exp. 14. \\lion water is forced through a capillary tube, of such a bore that it is discharged only in succes sh e drops, it will how in a constant and accelerated stream when the tube is electrified, and the acceleration will be inversely proportional to the diameter of the bore. This fact seems to be denied by Carmoy. See J01101. de
Physique, xlv. 106.
Exp. 15. A capillary syphon, which discharges cold watt]• only by drops, will discharge water of a higher temperature in a continued stream.
Exp. 16. Let a capillary tube be held in a position inclined to the horizon, and let a drop of liquid be let fall upon its surface, then bringing the tube into a vertical position at the instant when the drop has arrived at the inferior orifice, the fluid will run through the orifice, and rise in the interior of the tube.
Exp. 17. if the preceding experiments with capilla ry tubes, excepting Exp. 9, be made in the exhausted receiver of an air pump, the fluids will rise to the same height as in the open air. • Exp. 18. If the bore of a capillary tube be lined with a very thin coating of grease, or any unctuous the water will not ascend in the tube.
Exp. 19. By observing carefully the upper surface of the column of fluid, elevated in capillary tubes, it will be found to be concave upwards. AI. Hauy found, that in capillary tubes of glass, of very small diameters, the con cave surfaces of water and of oils differ very little from the form of a hemisphere.
Exp. 20. If the capillary tube is taken out of the fluid in which it is immersed, and inclined to the horizon so that the included fluid may obey the action of gravity, the concavity will appear at both ends of the column, and suffers no variation either in its shape or size, whether the tube be held in a vertical, a horizontal, or an oblique direction.
Exp. 21. When the column of water is thus made to move along the tube, it seems to suffer a resistance as it approaches to either end, and it does not completely reach the extremity of the tube till the tube is almost inverted.
Exp. 22. When a capillary tube is immersed in mer cury, or in any metal in a state of fusion, the fluid, instead of rising, is depressed in the tube below the general level. See Plate CX. Fig. 4. Gellert found that when a glass tube was immersed in melted lead, the depression mul tiplied by the bore was 0.054. Messrs flatly and Tre mery found, that the depression of mercury in a capillary tube one thousandth part of a metre in diameter, or 0.039371 of an English inch, was 0.2887 of an English inch, the product being .01137. The ultimate product inferred from Lord Charles Cavendish's experiments is .015.