reduced to four times the diameter of the base, without the light being
thereby rendered any the less bright. As for the height to be given the
convergent cone, B, that is determined by the opening of the angle
according to which it has been constructed. Finally, as a general thing,
the diameter of the small base should be equal to half the large base of
the convergent cone, B.

The new chimney should be placed upon the holder in such a way that the
upper part of the wick tube, D, is a few millimeters beneath the base of
the convergent cone. The height to be given the wick varies according to
the lamp used. It is regulated so as to obtain a steady and regular
combustion. In oil lamps it must project about 1½ centimeters. If two
lamps of the same size be observed, one of which is fitted with the new
chimney and the other with the old style, we shall be struck with the
difference that exists in the color of the flame as well as in its
intensity. While in the case of the cylindrical glass the flame is red and
dull, in that of the circuit it is white and very bright. This, however,
is not surprising when we reflect upon the theoretical conditions upon
which the construction of the new chimney is based--the strong influx of
air having the result of causing a more active combustion of the liquid,
and consequently of raising to white heat the particles of carbon
disseminated through the flame. As it was of interest to ascertain what
the increase of illuminating power was in a given lamp provided with the
new chimney, Mr. Felix le Blanc undertook some photometric experiments.
The trials were made with a Gagneau lamp provided with a chimney of the
ordinary shape, and then with one of Mr. Bayle's. The measurements were
made after each had been burned half an hour. The light of the standard
Carcel lamp being 1, there was obtained with the Gagneau lamp with the
ordinary chimney 1.113 carcels, and with the Bayle chimney 1.404 carcels.
Thus 1.113:1.404 represents the ratio of the same lamp with the ordinary