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238 FRAGMENTS OF SCIENCE.

ter are arranged together. In 1853 I also published a
paper “On Molecular Influences,” in which common heat
was made the explorer of organic structure. In the “ Ba-
kerian Lecture,” given before the Royal Society in 1855,
the same idea and phraseology crop out. The Bakerian
Lecture for 1864 bears the title “ Contributions to Molec-
ular Physics.” And all through the investigations which
have occupied me during the last ten years, my wish and
aim have been to make radiant heat an instrument by
which to lay hold of the ultimate particles of matter.

The labors now to be considered lie in the same direc-
tion. In the researches just referred to, tubes of glass and
brass were employed, called, for the sake of distinction,
“ experimental tubes,” in which radiant heat was acted
upon by the gases and vapors subjected to examination.
Two or three months ago, with a View of seeing what oc-
curred within these tubes on the entrance of the gases or
vapors, it was found necessary to intensely illuminate their
interiors. The source of illumination chosen was the elec-
tric light, the beam of which, converged by a suitable lens,
was sent along the axis of the tube. The dirt and filth in
which we~ habitually live were strikingly revealed by this
method of illumination. For, wash the tube as we might
with water, alcohol, acid, or alkali, until its appearance in
ordinary daylight was that of absolute purity, the delusive
character of this appearance was in most cases revealed by
the electric beam. In fact, in air so charged with sus-'
pended matter as that which supplies our lungs in London,
it is not possible-to be more than approximately clean.

Vapors of various kinds were sent into a glass experi-
mental tube, a yard in length, and about three inches in
diameter. As a general rule, the vapors were perfectly
transparent; the tube, when they were present, appearing
as empty as when they were absent. In two or three cases,
however, a faint cloudiness showed itself within the tube.

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