Ocroser 11, 1918] 
culties in the way of attempts at such a con- 
ception for real space, but even in the hypo- 
thetical space a continuous ether would find 
obstacles to the exercise of its principal func- 
tion which is “to undulate.” Moreover there 
would be no particular object in undulating— 
nothing to incite undulation—and so from all 
angles the ether idea has a rather hard strug- 
gle for a real existence. 
We deduce properties of the circle by as- 
suming that it is possible to divide the con- 
tinuously curved circumference into parts so 
small that each one will be a straight line, and 
the rigid accuracy of the results so obtained is 
in no degree vitiated by the fact that the as- 
sumption can not possibly be true. Likewise 
we may deal with physical phenomena as 
though there were a “medium,” an all pervad- 
ing plenum of substance, itself devoid of grav- 
ity and of most other properties of real matter 
saving only the capacity to undulate. We can 
deduce, explain and predict with entire suc- 
cess—with consistent results and even aston- 
ishing confirmations—notwithstanding our me- 
dium or ether may be entirely hypothetical, 
its assumed properties may be contradictory in 
themselves, and it may not be possible for such 
an imaginary medium to have a real objective 
existence. 
To locate and corner the remaining major 
difficulty in the way of a full comprehension 
of things of nature will at least contribute to 
our plans and measures for mobilization of 
forces and will indicate the main objective 
and the methods of attack, even if the adver- 
sary shall prove forever invincible. 
Body B is separated from body A by an in- 
tervening distance. It is not possible for an 
“impulse” of mutual influence which requires 
time for the passage to be in transit between 
A and B, to be disconnected from both for the 
moment—suspended between them in other 
words—without any intervening medium ex- 
cept space? What a flood of light and clarity 
would be shed on and through the accumulated 
mass of physical facts and data, as well as the 
tangled maze of speculative perplexities, if an 
affirmative answer to this conundrum could 
only be given. 
SCIENCE 
359 
No confession of individual faith can be 
claimed to be of itself a useful contribution 
to our knowledge of material things, and this 
is distinctly true so far as concerns the ideas 
of the undersigned, but as has recently been 
said by a distinguished physicist it is well 
sometimes to declare ourselves in this respect 
“for this naturally has its influence upon all 
that is said and done and to the end of making 
the point of view of the writer clearly under- 
stood.” (Crehore) It will be advantageous for 
the reader if he can feel that the writer is 
setting forth ideas with a certain degree of 
self felt confidence and “ intellectual rest.” I 
will therefore add the following, which is 
stated partly in the first person since it is a 
sort of individually conceived framework or 
background on which to pin ideas and new 
facts; frequently with a satisfactory fit in 
place, sometimes for the moment quite de- 
tached from the general pattern, but as a rule 
with a constant tendency towards accordance 
with what may ultimately turn out to be a 
complete and consistent picture. 
There is only one kind of real space, the 
kind of everyday experience. 
There is no material substance that does 
not have the common attribute of gravity. 
There is no “force” except gravity, and all 
physical phenomena are resolvable into this 
conception. 
Gravity is an inherent, essential, and uni- 
versal attribute of matter. It is and ever 
will remain inexplainable. What is more (and 
this is another paradox) if an “ explanation” 
were possible this would actually be a retro- 
grade step in the progress of knowledge, since 
we would then have at least one remaining 
mystery on our hands, almost certainly still 
more troublesome than is that of gravity. 
There is no such real thing as a continuous 
medium or ether. This however in no manner 
or degree disparages the vast majority of the 
facts, results and predictions that have been 
accumulated and accomplished on the “as 
though there were” assumption regarding an 
ether, nor is it inconsistent with the confident 
belief that there will be very many additional 
real and useful developments and advances in 
