268 Prof. Whewell’s Demonstration 
And the smallest admixture of the weightless element is sufficient to 
prevent the weight cone _— taken as the measure of the quantity of 
matter. 
~ But on this Lignctintcin how are we to distinguish such compounds 
Pein bodies consisting purely of heavy matter ? How are we to satisfy 
ourselves that there is not, in every body, some admixture, small or 
great, of the weightless element? If we call this element phlogiston, 
how shall we know that the bodies with which we have to do are, any of 
them, absolutely free from phlogiston ? nit 
“ We cannot refer to the weight for any such assurance; for by sup- 
position the presence and absence of phlogiston makes no difference in 
the weight. Nor can any other properties secure us at least from a 
very ore clomacasoney' for to assert that a mixture of Fin 100 or 1 in 
10 of would always manifest itself in the properties of the 
body, must be an arbitrary procedure, till we have proved this assertion 
wy: experiment ; and we cannot do this till we have learnt some mode 
‘the quantities of matter in bodies and. parts of bodies ; 
wich is exactly what we question the possibility 6f, in the present 
ypothesis. 
“Thus, if we assume the existence of an element, phlogiston, devoid 
of weight, we cannot be sure that every body does not contain some 
portion of this element; while we see that if there be an admixture of 
such an element, the weight is no longer any criterion of the quantity 
of matter. And thus we have proved, that if there be any kind of mat- 
ter which is not heavy, the weight can no longer avail us, in any case or 
to any extent, as a measure of the quantity of matter. 
» Tmay remark, that the same conclusion is easily extended to the 
case in which phlogiston is supposed to have absolute levity ; for m 
that case, a certain mixture of phlogiston and of heavy matter would 
have no weight, and might be — for oe in the #4 
ceding reasoning. 
“I may remark also, that the same wuebeie would follow, by ~ 
‘same reasoning, if any kind of matter, instead of being void of weight 
‘were heavy indeed, but not so heavy, in proportion to ite quantityof 
epee as other kinds. 
~ “On all these hypotheses there would be no possibility of measuring 
re mnatter by weight at all, in any case, or to any extent. 
pehretives ‘bevurged, that we have not yet reduced the hypothesis 
for mathematicians 
measure quay of mater, not but me other va 
of. while > eared ab aby eee 
“aT TTR tae eh ony: oe ae? he ge yee Care Se TR IN ay 
lc = 
