SCIENTIFIC MA TERIA LISM. 401 
ings and yearnings of the scientific intellect are directed 
in vain. 
But here your tolerance will be needed. It was the 
American Emerson, I think, who said that it is hardly 
possible to state any truth strongly, without apparent 
injustice to some other truth. Truth is often of a dual 
character, taking the form of a magnet with two poles; 
and many of the differences which agitate the thinking 
part of mankind are to be traced to the exclusiveness with 
which partisan reasoners dwell upon one half of the dual- 
ity, in forgetfulness of the other. The proper course 
appears to be to state both halves strongly, and allow each 
its fair share in the formation of the resultant conviction. 
But this waiting for the statement of the two sides of a 
question implies patience. It implies a resolution to sup- 
press indignation, if the statement of the one half should 
clash with our convictions; and to repress equally undue 
elation, if the half-statement should happen to chime in 
with our views. It implies a determination to wait calmly 
for the statement of the whole, before we pronounce 
judgment in the form of either acquiescence or dissent. 
This premised, and I trust accepted, let us enter upon 
our task. There have been writers who affirmed that the 
pyramids of Egypt were natural productions; and in his 
early youth Alexander von Humboldt wrote a learned essay 
with the express object of refuting this notion. We now 
regard the pyramids as the work of men's hands, aided 
probably by machinery of which no record remains. We 
picture to ourselves the swarming workers toiling at those 
vast erections, lifting the inert stones, and, guided by the 
volition, the skill, and possibly at times by the whip of the 
architect, placing them in their proper positions. The 
blocks, in this case, were moved and posited by a power 
external to themselves, and the final form of the pyramid 
expressed the thought of its human builder. 
Let us pass from this illustration of constructive power 
to another of a different kind. When a solution of common 
salt is slowly evaporated, the water which holds the salt in 
solution disappears, but the salt itself remains behind. At 
a certain stage of concentration the salt can no longer retain 
the liquid form; its particles, or molecules, as they are 
called, begin to deposit themselves as minute solids so 
minute, indeed, as to defy all microscopic power. As evap- 
