78 
SIR B. C. BR0D1E ON THE CALCULUS OE CHEMICAL OPERATIONS. 
mixed up with the symbolical forms in which they originate, that it would be inexpedient 
and indeed almost impracticable, to attempt to explain these conceptions except in 
reference to these forms, and these definitions will be given as the occasion arises. 
A chemical equation has been hitherto regarded in this Calculus only as an assertion 
in regard to the identity of certain units of ponderable matter. But there is another 
and equally just point of view from which such an equation may be considered, namely, 
as the record of a “chemical event” or “metamorphosis;” and a chemical equation of 
the form u =- 0 may correctly be termed the symbol of such an event. For from the 
very principle on which such equations are constructed, the assertion that A is identical 
as regards “ weight ” with B necessarily implies that A has been chemically converted 
into B, or that B has been chemically converted into A, for otherwise we could not 
possibly have been aware of this identity, our only knowledge of the identical 
relation of matter being derived, as has already been fully explained (I. Sec. VI.), from 
the chemical transmutation of matter. And when we write down such equations as 
those given in the last section (Sec. I. (2)(3)), we are recording the various events of 
which we have become cognizant in the history of chemical metamorphosis. 
The term “chemical event” will be here employed to denote the occurrence of any 
change whatever in the chemical composition of the units of matter of which the result 
is or may be expressed in an equation ; and precisely as we speak of a “ chemical 
operation ” as the “ simple weight ” which is the result of that operation, so also may 
we refer to a “ chemical equation” as the “ chemical event” of which it symbolizes the 
result, and deal with it as representing the event itself. Such an event is here repre- 
sented to us as in the strictest sense a “metamorphosis” or “change of form;” not 
that we venture to offer any material image, picture, or physical representation of that 
as yet inscrutable phenomenon, but we speak of it in this language because that change is 
indicated to us and adequately expressed by changes in the arrangement and structure 
of these symbolic forms, through which it is brought under the cognizance of our intel- 
ligence. 
(2) Now just as the algebraical sum or aggregate (as we shall term it) of two or more 
equations itself constitutes an equation, so every collection or aggregate of chemical 
events constitutes an event. This is true whether those events are considered as 
occurring successively or simultaneously. An event of which the result is expressed by 
the algebraical sum of two or more equations will be termed “ an aggregate,” and will be 
spoken of as “ the aggregate ” of those two or more events expressed in those equations, 
and will be said to be “ constituted ” of those events. We are hence led to discriminate 
chemical events as “simple” and “compound” events. 
Definition. — A “ compound ” event is an event which is regarded in the system 
of events under our consideration, whatever that may be, as “ constituted ” of two or 
more events, and “a simple event” is an event which in that system is not so regarded. 
But these terms necessarily have reference to some special mode of regarding and 
considering the phenomena, and apart from such considerations the terms are unmeaning ; 
