violet glass. When, however, Dr. Von Bezold, as
above, asserts that the violet rays have such and such an effect, he
means the violet of the spectrum, which has its specific duty to
perform in the compound light of which it is a necessary portion. But
the violet light of the spectrum and filtered violet sunlight are
altogether different things. The first, as our valued contributor Dr.
Van der Weyde has very clearly pointed out, is "a homogeneous color
containing, besides the luminous, the invisible chemical rays without
any caloric rays; while the light colored by passing through violet
glass is a mixture of blue rays with the red rays at the other end of
the spectrum; and it contains a quantity of the chemical rays
belonging to the blue and the caloric rays belonging to the red. In
fact, violet glass passes a light identical with sunlight, only much
reduced in power, containing but a portion of its caloric, chemical,
and luminous agency: being simply deprived of its strongest rays." And
this the spectroscope has clearly demonstrated. Reduced to its
simplest terms, then, the necessary conclusion is that the violet
glass acts purely as a shade for decreasing the intensity of the solar
light. And in the simple fact that it does so serve as a shade lies
the sole virtue (if any there be) of the glass. In 1856, Dr. Daubeny
made experiments on the germination of seeds, and in his report is
this suggestive sentence: "In a south aspect, indeed, light which had
passed through the ammonia sulphate of copper (blue solution), and
even darkness itself, seemed more favorable than the whole of the
spectrum; but this law did not seem to extend to the case of seeds
placed in a northern aspect where the total amount of light was less
considerable."

In our next issue, we shall review the effects of light and darkness
upon the animal organization, and endeavor to account for the curing
of diseases and the production of other phenomena which have been
erroneously ascribed to the influence of the blue filtered sunlight.

* * * * *

THE WETLI MOUNTAIN RAILROAD AND ITS DISASTROUS TRIAL TRIP.

Among the various means proposed of late years for building lines of
railroad on the steep slopes of mountains, that of M. Wetli, of
Zurich, Switzerland, has attracted considerable attention from
European engineers. We have already laid before our readers the system
of central toothed rails used on the Righi and