11 
welded together, by data culled from every phase of Biological 
inquiry. Sometimes the principle of classification may legitimately 
embrace the consideration of purely chemico-vital manifestations ; 
and in the case of Zoology, we have seen that it may prominently 
involve a recognition of deep-seated anatomical appearances. 
Before leaving this part of our subject, I may observe that the 
principle of classification is intimately associated with the study of 
Morphology ; but at this stage of the discourse I can do no more 
than refer to one particular generalisation, which has also an impor- 
tant bearing on the hypothesis first submitted to your notice. It 
is this, viz., that “ the variation of all animal and vegetable forms 
is subject to a law of geometrical proportion.” We cannot now 
follow up this inquiry ; yet I venture to think that, in addition to 
the curious results obtained by Mr Hay in reference to the applica- 
tion of mathematical principles to the aesthetics of the human 
figure, and likewise to those obtained by Professors Mosely, M‘Cosh, 
and others, in respect of the forms of shells and plants — in addition, 
I repeat, to these (associated with other like generalisations, such 
as the “law of spiral development” and the “law of numerical pro- 
portion”), I think it can be shown that similar geometrical laws are 
applicable to the harmonies noticeable in Zoological affinity, and, 
possibly also, to the distribution of species. Be that as it may, all 
nature is but a cycle of harmonies, wheel within wheel ; but the 
relation of the enclosed spheres is so complicated, that to fathom 
the resources of any group of them requires a combination of powers 
beyond the reach of any single individual. 
Bearing in mind the practical considerations I have in view, 
permit me in the next place to direct your attention more par- 
ticularly to the educational value of the Natural History Sciences. 
The study of Geology, Zoology, and Botany, collectively or in 
part, may be rendered more or less subservient in every walk of 
life ; and even to those who pursue these sciences as a source of 
intellectual gratification they offer peculiar advantages. All of 
them are fit and easily-accessible sciences for training the mental 
powers of observation, and, at the same time, if allowed to exer- 
cise their full and legitimate sway, they are eminently calculated 
to advance our social interests. Let me put this more precisely. 
In the daily routine of life, whatever direction our duties may 
take, or whatever character they may assume, it is admitted by 
all that nothing is more essential than a well-regulated mind, able 
to observe, to store up, and to form a correct estimate of the 
value of facts ; and the possession of an intellect of this discerning 
habit is of immense importance, not only in the acquisition of 
knowledge, but in the formation of correct opinions. It is granted, 
indeed, that in so far as the requirements of a man of narrow 
sympathies are concerned, a fair amount of the so-called common- 
sense principle may be all that is absolutely necessary for his 
material advancement ; yet, if we desire the higher intellectual 
