Some little practice may be required before you can obtain this mental impression of the long tube, although some students seem to be able to produce it fairly well at the first trial. You, of course will have secured the necessary passive condition in yourself. The next step is to produce the mental impression of the tubular connection. This will appear first as a faint, shadowy ring, which by degrees will become more distinct, and will resolve itself into the shape of an open end of a tube. The tube will then lengthen out, and, later on, you will be able to see clear along its enormous length. You may obtain this result in a few experiments, and, on the other hand, may be required to practice it a number of times. It seems to be greatly a matter of obtaining the "knack" of forming the mental picture. You may obtain good results without the production of the tubular effect, but the best results seem to be obtained by those who can produce this effect.