DECEMBER 8, 1899. ] 
and work. Let us recognize the eras when 
great thoughts have been introduced into 
our subject and let us honor the great men 
who introduced and proved them correct. 
Let us forever reject such foolish ideas as 
the equality of mankind and carefully give 
the greater credit to the greater man. So, 
in choosing the subjects for our investiga- 
tion, let us, if possible, work upon those 
subjects which will finally give us an ad- 
vanced knowledge of some great subject. 
I am aware that we cannot always do this ; 
our ideas will often flow in side channels; 
but, with the great problems of the Uni- 
verse before us, we may sometime be able 
to do our share toward the greater end. 
What is matter; what is gravitation ; 
what is ether and the radiation through it; 
what is electricity and magnetism ; how are 
these connected together and what is their 
relation to heat? These are the greater 
problems of the universe. But many in- 
finitely smaller problems we must attack 
and solve before we can even guess at the 
solution of the greater ones. 
In our attitude toward these greater 
problems how do we stand and what is the 
foundation of our knowledge ? 
Newton and the great array of astron- 
omers who have succeeded him have proved 
that, within planetary distances, matter at- 
tracts all others with a force varying in- 
versely as the square of the distance. But 
what sort of proof have we of this law? 
It is derived from astronomical observa- 
tions on the planetary orbits. It agrees 
very well within these immense spaces; but 
where is the evidence that the law holds for 
smaller distances? We measure the lunar 
distance and the size of the earth and com- 
pare the force at that distance with the 
force of gravitation on the earth’s surface. 
But to do this we must compare the matter 
in the earth with that in the sun. This we 
ean only do by assuming the law to be 
proved. Again, in descending from the 
SCIENCE. 
827 
earth’s gravitation to that of two small 
bodies, as in the Cavendish experiment, we 
assume the law to hold and deduce the mass 
of the earth in terms of our unit of mass. 
Hence, when we say that the mass of the 
earth is 54 times that of an equal volume of 
water we assume the law of gravitation to be 
that of Newton. Thus a proof of the law 
from planetary down to terrestrial distances 
is physically impossible. 
Again, that portion of the law which says 
that gravitational attraction is proportional 
to the quantity of matter, which is the same 
as saying that the attraction of one body by 
another is not affected by the presence of a 
third, the feeble proof that we give by 
weighing bodies in a balance in different 
positions with respect to each other cannot 
be accepted on a larger scale. When we 
can tear the sun into two portions and 
prove that either of the two halves attracts 
half as much as the whole, then we shall 
have a proof worth mentioning. 
Then as to the relation of gravitation 
and time what can we say? Can we for a 
moment suppose that two bodies moving 
through space with great velocities have 
their gravitation unaltered? I think not. 
Neither can we accept Laplace’s proof that 
the force of gravitation acts instantaneously 
through space, for we can readily imagine 
some compensating features unthought of 
by Laplace. 
How little we know then of this law 
which has been under observation for two 
hundred years ! 
Then as to matter itself how have our 
views changed and how are they constantly 
changing. The round hard atom of New- 
ton which God alone could break into 
pieces has become a molecule composed of 
many atoms, and each of these smaller 
atoms has become so elastic that after vi- 
brating 100,000 times its amplitude of vi- 
bration is scarcely diminished. It has be- 
come so complicated that it can vibrate 
