cs will not travel
beyond it. The present hypothesis suffices for grouping known facts,
and it will doubtless enable many more to be foreseen, while new
successes will further increase its possessions.

Then the day will arrive when, like all those which have shone before
it, this seductive hypothesis will lead to more errors than
discoveries. It will, however, have been improved, and it will have
become a very vast and very complete edifice which some will not
willingly abandon; for those who have made to themselves a comfortable
dwelling-place on the ruins of ancient monuments are often too loth to
leave it.

In that day the searchers who were in the van of the march after truth
will be caught up and even passed by others who will have followed a
longer, but perhaps surer road. We also have seen at work those
prudent physicists who dreaded too daring creeds, and who sought only
to collect all the documentary evidence possible, or only took for
their guide a few principles which were to them a simple
generalisation of facts established by experiments; and we have been
able to prove that they also were effecting good and highly useful
work.

Neither the former nor the latter, however, carry out their work in an
isolated way, and it should be noted that most of the remarkable
results of these last years are due to physicists who have known how
to combine their efforts and to direct their activity towards a common
object, while perhaps it may not be useless to observe also that
progress has been in proportion to the material resources of our
laboratories.

It is probable that in the future, as in the past, the greatest
discoveries, those which will suddenly reveal totally unknown regions,
and open up entirely new horizons, will be made by a few scholars of
genius who will carry on their patient labour in solitary meditation,
and who, in order to verify their boldest conceptions, will no doubt
content themselves with the most simple and least costly experimental
apparatus. Yet for their discoveries to yield their full harvest, for
the domain to be systematically worked and desirable results obtained,
there will be more and more required the association of willing minds,
the solidarity of intelligent scholars, and it will be also necessary
for these last to have at their disposal the most delicate as well as
the most powerful instruments. These are conditions paramount at the
present day for continuous progress in exp