; the latter were divided into equal volumes, and the velocity of the water was deduced from the section of the tubes, and from the time of efflux of half a litre.
The apparatus above described was only employed for the experiments with water in motion: with some modifications it might also be used for air; but my experiments on moving air had been previously made with a slightly different apparatus, of which more hereafter, and the results had been found quite conclusive. I had already proved that the motion of air produces no appreciable displacement of the bands. But I shall return to this result and give further details.
For water there is an evident displacement. The bands are displaced towards the right when the water recedes from the observer in the tube at his right, and approaches him in the tube on his left.
The displacement of the bands is towards the left when the direction of the current in each tube is opposite to that just defined.
During the motion of the water the bands remain well defined, and move parallel to themselves, without the least disorder, through a space apparently proportional to the velocity of the water. With a velocity of
even, the displacement is perceptible; for velocities between
it is perfectly measureable.
In one experiment, where a band occupied five divisions of the micrometer, the displacement amounted to