2 
I think it right to state at the outset that I propose to adduce 
arguments, drawn both from physical science and from Scrip- 
ture, which lead to the conclusion that this view of the 
quality of matter is untrue. 
2. Taking, first in order, the arguments which have relation 
to physical science, I have no hesitation in beginning with the 
admission that chemical experiments have shown that whatever 
modifications substances may undergo by analysis or synthesis, 
and in whatever way different substances may be combined, 
the quantity of matter as measured, either by the number of 
the indivisible elements, or by weight, remains unchanged. 
Such experimental facts seem to have suggested the idea of 
the indestructibility of matter, and the inference would be 
perfectly valid if physical science consisted exclusively of 
what is known by experiment, and if we could learn nothing 
about matter beyond what experiment teaches. But I shall 
maintain that this is not a true definition of physical science , 
inasmuch as such science, when complete, rests not on ex- 
periment alone, but on experiment combined with reasoning. 
Experiment may establish laius, but science perfected consists 
in giving reasons for laws. The conclusion to which the argu- 
ment I am about to adduce relative to the intrinsic quality of 
matter points, wholly depends on this twofold character of 
physical science, and on the mutual relation of the two parts ; 
but before entering upon the general argument, it is necessary 
to go through a preliminary discussion of the nature of the 
facts with which we are concerned in physics. These facts 
are not all of the same kind, but range themselves under two 
essentially different categories. 
3. The last assertion may be exemplified by the following 
familiar instance. From ordinary experience we know that 
sounds , whether unmusical or musical, are generated by agita- 
tions produced in the air : if, guided by experiment, we 
define the air to be a perfectly elastic fluid substance, pressing 
always in exact proportion to its density if its temperature 
be given, and susceptible of no change as to quantity by states 
of pressure or motion, we can, according to the principles of 
the science of Hydrodynamics, obtain differential equations, 
the complete solution of which would be adequate to tell us 
tho consequences which result from certain disturbances of 
the fluid produced under given circumstances. In particular, 
we might thus ascertain, in the instances of disturbances which 
are found to generate musical sounds, what are the laws of 
the movements and variations of pressure of the air that pro- 
duce this effect. It would, in fact, be thereby shown that 
the movements are vibratory, that they are subject to a law 
of propagation, and that being accompanied by variations of 
