comparing them with the cathode rays. They
suppose, for instance, that the rays are formed by electrons animated
with so great a velocity that their inertia, conformably with theories
which I shall examine later, no longer permit them to be stopped in
their course; this is, for instance, the theory upheld by Mr
Sutherland. We know, too, that to M. Gustave Le Bon they represent the
extreme limit of material things, one of the last stages before the
vanishing of matter on its return to the ether.

Everyone has heard of the N rays, whose name recalls the town of
Nancy, where they were discovered. In some of their singular
properties they are akin to the X rays, while in others they are
widely divergent from them.

M. Blondlot, one of the masters of contemporary physics, deeply
respected by all who know him, admired by everyone for the penetration
of his mind, and the author of works remarkable for the originality
and sureness of his method, discovered them in radiations emitted from
various sources, such as the sun, an incandescent light, a Nernst
lamp, and even bodies previously exposed to the sun's rays. The
essential property which allows them to be revealed is their action on
a small induction spark, of which they increase the brilliancy; this
phenomenon is visible to the eye and is rendered objective by
photography.

Various other physicists and numbers of physiologists, following the
path opened by M. Blondlot, published during 1903 and 1904 manifold
but often rather hasty memoirs, in which they related the results of
their researches, which do not appear to have been always conducted
with the accuracy desirable. These results were most strange; they
seemed destined to revolutionise whole regions not only of the domain
of physics, but likewise of the biological sciences. Unfortunately the
method of observation was always founded on the variations in
visibility of the spark or of a phosphorescent substance, and it soon
became manifest that these variations were not perceptible to all
eyes.

No foreign experimenter has succeeded in repeating the experiments,
while in France many physicists have failed; and hence the question
has much agitated public opinion. Are we face to face with a very
singular case of suggestion, or is special training and particular
dispositions required to make the phenomenon apparent? It is not
possible, at the present moment, to declare the problem solved; but
very recent experiments by