splinters of colourless glass acted powerfully, nevertheless, after it
was dark, I put on, by the aid of a single tallow candle, as quickly as
possible, particles of cork and glass on the glands of a dozen
tentacles, as well as some of meat on other glands, and covered them up
so that not a ray of light could enter; but by the next morning, after
an interval of 13 hrs., all the particles were carried to the centres
of the leaves.

These negative results led me to try many more experiments, by placing
particles on the surface of the drops of secretion, observing, as
carefully as I could, whether they penetrated it and touched the
surface of the glands. The secretion, from its weight, generally forms
a thicker layer on the under than on the upper sides of the glands,
whatever may be the position of the tentacles. Minute bits of dry cork,
thread, blotting paper, and coal cinders were tried, such as those
previously employed; and I now observed that they absorbed much more of
the secretion, in the course of a few minutes, than I should have
thought possible; and as they had been laid on the upper surface of the
secretion, where it is thinnest, they were often drawn down, after a
time, into contact with at least some one point of the gland. With
respect to the minute splinters of glass and particles of hair, I
observed that the secretion slowly spread itself a little over their
surfaces, by which means they were likewise drawn downwards or
sideways, and thus one end, or some minute [page 30] prominence, often
came to touch, sooner or later, the gland.

In the foregoing and following cases, it is probable that the
vibrations, to which the furniture in every room is continually liable,
aids in bringing the particles into contact with the glands. But as it
was sometimes difficult, owing to the refraction of the secretion, to