4 REPORT—1868. 
Polarized light is especially useful and powerful here. A beam of such light, when 
sent in among the molecules of a crystal, is acted on by them, and from this action 
we infer with more or less of clearness the manner in which the molecules are 
arranged. The difference, for example, between the inner structure of a plate of 
rock-salt and a plate of crystallized sugar or sugar-candy is thus strikingly revealed. 
These differences may be made to display themselves in phenomena of colour of 
great splendour, the play of molecular force being so regulated as to remove certain 
of the coloured constituents of white light, and to leave others with increased in- 
tensity behind. 
And now let us pass from what we are accustomed to regard as a dead mineral 
to a living grain of corn. When ?t is examined by polarized light, chromatic phe- 
nomena similar to those noticed in crystals are observed. And why? Because the 
architecture of the grain resembles in some degree the architecture of the crystal. 
In the corn the molecules are also set in definite positions, from which they act 
upon the light. But what has built together the molecules of the com? I have 
already said regarding crystalline architecture that you may, if you please, con- 
sider the atoms and molecules to be placed in position by a power external to 
themselves. The same hypothesis is open to you now. But if in the case of 
erystals you have rejected this notion of an external architect, I think you are bound 
to reject it now, and to conclude that the molecules of the corn are self-posited by 
the forces with which they act upon each other. It would be poor philosophy to 
invoke an external agent in the one case and to reject it in the other. 
Instead of cutting our grain of corn into thin slices and subjecting it to the action 
of polarized light, let us place it in the earth and subject it to a certain degree of 
warmth. In other words, let the molecules, both of the corn and of the surrounding 
earth, be kept in a state of agitation ; for warmth, as most of you know, is, in the 
eye of science, tremulous molecular motion. Under these circumstances, the grain 
and the substances which surround it interact, and a molecular architecture is the 
result of this interaction. A bud is formed ; this bud reaches the surface, where it 
is exposed to the sun’s rays, which are also to be regarded as a kind of vibratory 
motion. And as the common motion of heat with which the grain and the sub- 
stances surrounding it were first endowed, enabled the grain and these substances 
to coalesce, so the specific motion of the sun’s rays now enables the green bud to 
feed upon the carbonic acid and the aqueous vapour of the air, appropriating those 
constituents of both for which the blade has an elective attraction, and permitting 
the other constituent to resume its place in the air. Thus forces are active at the 
root, forces are active in the blade, the matter of the earth and the matter of the 
atmosphere are drawn towards the plant, and the plant augments in size. We 
have in succession the bud, the stalk, the ear, the full corn in the ear. For the 
forces here at play act in a cycle which is completed by the production of grains 
similar to that with which the process began. 
Now there is nothing in this process which necessarily eludes the power of mind 
as we know it. An intellect the same in kind as our own would, if only suffi- 
ciently expanded, be able to follow the whole process from beginning to end. No 
entirely new intellectual faculty would be needed for this purpose. The duly ex- 
panded mind would see in the process and its consummation an instance of the play 
of molecular force. It would see every molecule placed in its position by the spe- 
cific attractions and repulsions exerted between it and other molecules. Nay, given 
the grain and its environment, an intellect the same in kind as our own, but suffi- 
ciently expanded, might trace out @ prior? every step of the process, and by the 
application of mechanical principles would be able to demonstrate that the cycle 
of actions must end, as it is seen to end, in the reproduction of forms like that with 
which the operation began. A similar necessity rules here to that which rules the 
planets in their circuits round the sun. 
You will notice that I am stating my truth strongly, as at the beginning we 
agreed it should be stated. But I must go still further, and affirm that in the eye 
of science the animal body is just as much the product of molecular force as the stalk 
and ear of corn, or as the crystal or salt of sugar. Many of its parts are obviously 
mechanical. Take the human heart, for example, with its exquisite system of 
valves, or take the eye or the hand. Animal heat, moreover, is the same in kind 
