iod of the rotation, that it is impossible to
predict at the present time the ultimate changes or modifications
in the climatic conditions which may follow. This commission has
considered most carefully the possible causes that may have been
responsible for this catastrophe--(_Weltunfall_)--and by
eliminating every hypothesis that was incapable of explaining all
of the various disturbances, is now in a position to present two
theories, either one of which appears to be capable of explaining
the recent disturbances.

The phenomena in question may be briefly summarized as follows;

1. THE YELLOW AURORA. In Northern Europe this appeared suddenly on
the night of July 22d as a broad, faint sheaf--(_Lichtbuendel_)--of
clear yellow light in the western sky. Reports from America show
that at Washington it appeared in the north as a narrow shaft of
light, inclined at an angle of about thirty degrees with the
horizon, and shooting off to the east. Near the horizon it was
extremely brilliant, and the spectroscope showed that the light was
due to glowing helium gas.

The Potsdam Observatory reported that the presence of sodium has
been detected in the aurora; but this appears to have been a mistake
due to the faintness of the light and the circumstance that no
comparison spectrum was impressed on the plate. On the photograph
made at the Washington Observatory the helium line is certain, as a
second exposure was made with a sodium flame; and the two lines are
shown distinctly separated.

2. THE NEGATIVE ACCELERATION. This phenomenon was observed
to a greater or less extent all over the globe. It was especially
marked near the equator; but in Northern Europe it was noted by only
a few observers, though many clocks were stopped and other
instruments deranged. There appears to be no doubt that a force of
terrific magnitude was applied in a tangential direction to the
surface of the earth, in such a direction as to oppose its axial
rotation, with the effect that the surface velocity was diminished
by about one part in three hundred, resulting in a lengthening of
the day by five minutes, thirteen and a half seconds.

The application of this brake--(_Bremsekraft_), as we may term
it--caused acceleration phenomena to manifest themselves precisely
as on