508 Meeting of the British Association. [ Oct., 
with the facts which scientific men have won, and with the great 
theories which they have elaborated. 
If we look at the face of a watch, we see the hour- and minute- 
hands, and possibly also a second-hand, moving over the graduated 
dial. Why do these hands move? and why are their relative 
motions such as they are observed to be? These questions can- 
not be answered without opening the watch, mastering its various 
parts, and ascertaining their relationship to each other. When this 
is done, we find that the observed motion of the hands follows of 
necessity from the inner mechanism of the watch when acted upon 
by the force invested in the spring. 
This motion of the hands may be called a phenomenon of art, 
but the case is similar with the phenomena of nature. These also 
have their inner mechanism, and their store of force to set that 
mechanism going. ‘The ultimate problem of physical science is 
to reveal this mechanism, to discern this store, and to show that 
from the combined action of both the phenomena of which they 
constitute the basis must of necessity flow. 
There have been writers who affirmed that the pyramids of 
Egypt were the productions of nature; and in his early youth 
Alexander von Humboldt wrote an 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 archi- 
tect, placing the stones in their proper positions. The blocks in 
this case were moved 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 building power to another 
of a different kind. When a solution of common salt is slowly 
evaporated, the water which holds the salt im solution disappears, 
but the salt itself remains behind. At a certain stage of concen- 
tration 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 evaporation continues solidification goes on, and we finally 
obtain, through the clustering together of immumerable molecules, 
a finite mass of salt of a definite form. What is this form? It 
sometimes seems a mimicry of the architecture of Egypt. We 
have little pyramids built by the salt, terrace above terrace from 
base to apex, forming thus a series of steps resembling those up 
which the Egyptian traveller is dragged by his guides. The 
human mind is as little disposed to look at these pyramidal salt- 
crystals without further question as to look at the pyramids of 
