158 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[August 21,1872. 
tecedent—the power which does the work—from the 
aggregate of material conditions under which that power 
may be distributed and applied. No doubt the term 
cause is very loosely employed in popular phraseology ; 
often (as Mr. Mill has shown) to designate the occurrence 
that immediately preceded the effect; as when it is said 
that the spark which falls into a barrel of gunpowder 
is the cause of its explosion, or that the slipping of a 
man’s foot off the rung of a ladder is the cause of his fall. 
But even a very slightly trained intelligence can distin¬ 
guish the power which acts in each case, from the condi¬ 
tions under which it acts. The force which produces the 
explosion is locked up, as it were, in the powder ; and 
ignition merely liberates it, by bringing about new 
chemical combinations. The fall of the man from the 
ladder is due to the gravity which was equally pulling 
him down while he rested on it; and the loss of support, 
either by the slipping of his foot, or by the breaking of 
the rung, is merely that change in the material condi¬ 
tions which gives the power a new action. 
Many of you have doubtless viewed with admiring in¬ 
terest that truly wonderful work of human design, the 
Walter Printing Machine. You first examine it at rest; 
presently comes a man who simply pulls a handle to 
wards him; and the whole inert mechanism becomes in¬ 
stinct with life,—the blank paper continuously rolling- 
off the cylinder at one end, being delivered at the other, 
without any intermediate human agency, as large sheets 
of print, at the rate of 15,000 in an hour. Now what is 
the cause of this most marvellous effect F Surely it lies 
essentially in the power or force which the pulling of the 
handle brought to bear on the machine from some ex¬ 
traneous source of power,—which we in this instance 
know to be a steam-engine on the other side of the wall. 
This force it is, which, distributed through the various 
parts of the mechanism, really performs the action of 
which each is the instrument; they only supply the 
vehicle for its transmission and application. The man 
comes again, pushes the handle in the opposite direction, 
detaches the machine from the steam-engine, and the 
whole comes to a stand; and so it remains, like an in¬ 
animate corpse, until recalled to activity by the renewal 
of its moving power. 
But, say the reasoners who deny that force is anything 
else than a fiction of the imagination, the revolving shaft 
of the steam-engine is “ matter in motion and when the 
connection is established between that shaft and the one 
that drives the machine, the motion is communicated from 
the former to the latter, and thence distributed to the 
several parts of the mechanism. This account of the 
operation is just what an observer might give, who had 
looked on with entire ignorance of everything but what 
his eyes could see ; the moment he puts his hand upon 
any part of the machinery, and tries to stop its motion, 
he takes as direct cognizance, through his sense of the 
effort required to resist it, of the force which produces 
that motion, as he does through his eye of the motion itself. 
Now, since it is universally admitted that our notion 
of the external world would be not only incomplete, but 
erroneous, if our visual perceptions were not supple¬ 
mented by our tactile, so, as it seems to me, our interpre¬ 
tation of the phenomena of the Universe must be very 
inadequate, if we do not mentally co-ordinate the idea of 
force with that of motion, and recognize it as the “ efficient 
cause ” of those phenomena,—the “ material conditions ” 
constituting (to use the old scholastic term) only “ their 
formal cause.” And I lay the greater stress on this point, 
because the mechanical philosophy of the present day 
tends more and more to express itself in terms of motion 
rather than in terms of force ,—to become kinetics instead 
of dynamics. 
Thus from whatever side we look at this question,— 
whether the common sense of mankind, the logical 
analysis of the relation between cause and effect, or the 
study of the working of our own intellects in the inter¬ 
pretation of nature,—we seem led to the same conclusion; 
that the notion of force is one of those elementary forms 
of thought with which we can no more dispense, than we 
can with the notion of space or of succession. And I 
shall now, in the last place, endeavour to show you that 
it is the substitution of the dynamical for the mere phe¬ 
nomenal idea, which gives their highest value to our 
conceptions of that order of nature, which is worshipped 
as itself a G-od by the class of interpreters whose doctrine 
call in question. 
The most illustrative as well as the most illustrious 
example of the difference between the mere generaliza¬ 
tion of phenomena and the dynamical conception that 
applies to them, is furnished by the contrast between the 
so-called laws of planetary motion discovered by the 
persevering ingenuity of Kepler, and the interpretation 
of that motion given us by the profound insight of New¬ 
ton. Kepler’s three laws were nothing more than com¬ 
prehensive statements of certain groups of phenomena 
determined by observation. The first, that of the revolu¬ 
tion of the planets in elliptical orbits, was based on the. 
study of the observed places of Mars alone ; it might or 
might not be true of the other planets ; for so far as 
Kepler knew, there was no reason why the orbits of 
some of them might not be the excentric circles which 
he had first supposed that of Mars to be. So Kepler’s 
second law of the passage of the Radius Vector over 
equal areas in equal times, so long as it was simply a 
generalization of facts in the case of that one planet,, 
carried with it no reason for its applicability to other 
cases, except that which it might derive from his er¬ 
roneous conception of a whirling force. And his third 
law was in like manner simply an expression of a certain 
harmonic relation which he had discovered between the 
times and the distances of the planets, having no more 
rational value than any other of his numerous hypotheses. 
Now the Newtonian “laws” are often spoken of as if 
they were merely higher generalizations in which Kepler’s- 
are included ; to me they seem to possess an altogether 
different character. For starting with the conception off 
two forces, one of them tending to produce continuous 
uniform motion in a straight line, the other tending to 
produce a uniformly accelerated motion towards a fixed 
point, Newton’s wonderful mastery of geometrical rea¬ 
soning enabled him to show that, if these dynamical 
assumptions be granted, Kepler’s phenomenal “laws,” 
being necessary consequences of them, must be univer¬ 
sally true. And while that demonstration would have 
been alone sufficient to give him an imperishable renown, 
it was his still greater glory to divine that the fall of the 
moon towards the earth—that is, the deflection of her 
path from a tangetial line to an ellipse— is a phenomenon 
of the same order as the fall of a stone to the ground 
and thus to show the applicability to the entire universe,, 
of those simple dynamical conceptions which constitute 
the basis of the geometry of the Principia. 
Thus, then, whilst no “ law ” which is simply a gene¬ 
ralization of phenomena can be considered as having any 
coercive action, we may assign that value to laws which 
express the universal conditions of the action of a force , the 
existence of which we learn from the testimony of our 
own consciousness. The assurance we feel that the 
attraction of gravitation must act under all circumstances, 
according to its one simple law, is of a very different, 
order from that which we have in regard (for example) 
to the laws of chemical attraction, which are as yet only 
generalizations of phenomena. And yet even in that 
strong assurance, we are required by our examination of 
the basis on which it rests, to admit a reserve of the. 
possibility of something different; a reserve which we. 
may well believe that Newton himself must have enter¬ 
tained. 
A most valuable lesson as to the allowance we ought 
always to make for the unknown “ possibilities of nature ” 
is taught us by an exceptional phenomenon so familiar 
that it does not attract the notice it has a right to claim. 
Next to the law of the universal attraction of masses of 
