of Edinburgh, Session 1869-70. 155 
spiritual nature, and is thus led to esteem the mere phantasms 
of his own imagination as proof of external agencies which may 
exist, hut which, by the terms of the hypothesis, cannot he veri¬ 
fied. Resolved into their ultimate elements, all the so-called 
proofs of spirit-life, when stated bona fide , are simply presentations 
to the consciousness of the inquirer’s own brain-work, as delusive 
as those of the lunatic or the dreamer. It has been commonly 
said that this class of inquirers are, for the most part, either of 
weak mind, or credulous, or ignorant. But this is not so. Here 
are delineations of the od-force, as investigated by Baron von 
Reichenbach, a skilled scientific inquirer. He never saw what is 
here represented as the manifestations of the od-force, he simply 
shows what was described to him as such by hysterical and 
morbidly nervous women ; and if they be true as descriptions, 
they are only representations to the consciousness of phantasmal 
brain-work. Some of these so-called spirit operations are instruc¬ 
tive illustrations of eesthetical automatic action of a cultivated 
brain. The emblem of a fellow of this Society, drawn by a person 
of high culture, is contrasted well with the uncouth mystical 
emblems of an uneducated female lunatic before me. I was assured 
by my late friend David Ramsay Hay, and no one was more com¬ 
petent to judge, that it is exactly true to the geometrical principles 
of form and colour. 
In the delusions of G-eorge Elliot we have an illustration of 
another interesting result of brain-work, the ideational evolution 
of the intuition of the infinite, a subject so much and so earnestly 
discussed by reflective philosophers, and which is equally as capable 
of biological illustration as the preceding. 
2. On Change of Apparent Colour by Obliquity of Vision. 
By Robert H. Bow, C.E., F.R.S.E. 
I discovered the peculiarity of chromatic vision, which is the 
subject of this paper, in the month of January, when conducting 
some experiments upon the perfection of definition at different parts 
of the retina; and I may introduce the subject by first referring to 
these experiments. 
In the case of ordinary sensation seated in the skin, there are 
