Thought Forms by Annie Besant and C.W. Leadbetter

As knowledge increases, the attitude of science toward the things of the invisible world is undergoing considerable modification. Its attention is no longer directed solely to the earth with all its variety of objects, or to the physical worlds around it; but it finds itself compelled to glance further afield, and to construct hypotheses as to the nature of the matter and force which lie in the regions beyond the ken of its instruments. The fact is that science has pressed its researches so far, has used such rare ingenuity in its questionings of nature, has shown such tireless patience in its investigations, that it is receiving the reward of those who seek, and forces and beings of the next higher plane of nature are beginning to show themselves on the outer edge of the physical field. " Nature makes no leaps ", and as the physicist nears the confines of his kingdom he finds himself bewildered by touches and gleams from another realm which interpenetrates his own. He finds himself compelled to speculate on invisible presences, if only to find a rational explanation for undoubted physical phenomena, and insensibly he slips over the boundary, and is, although he does not yet realize it, contacting the astral plane.

1901