mpossible to
attempt any quantitative measurement of their optical properties on
account of large waves curling round corners. The lecturer had succeeded
in producing the shortest waves, with frequency of 50,000 millions of
vibrations per second, the particular invisible radiation being only
thirteen octaves below visible light. His generator produced the small
sharp beam which alone could be employed for quantitative measurements.
By means of this apparatus experiments on electric radiation could be
carried on with as much certainty as could experiments with ordinary
light. Prof. Bose then performed experiments illustrative of the
properties possessed in common by light waves and electric waves. He
exhibited the power of selective absorption to electric rays displayed
by many substances pointing out that while water stopped them, pitch,
coal tar, and others were quite transparent to them. He showed how the
rays were reflected by mirrors, obeying the same laws as light. The hand
of the experimenter was found to be a good reflector, the rays
rebounding after impact. Electric rays also undergo refraction and he
described an ingenious method he had devised by which the index of
refraction of numerous opaque substances could be obtained with the
highest exactitude. In conclusion he gave an account of his discovery of
the polarisation of electric rays by crystals. He showed that these
polarised the electric rays just as they did ordinary light. He further
proved that substances under pressure and strain could produce double
refraction in them, as did glass under the same conditions in light.
Tourmaline was useless for electric rays; but a lock of human hair was
extraordinarily efficient. According to this theoretical prediction, an
ordinary book was shown to exhibit selective absorption in a striking
manner. Thus while the Calcutta University Calendar was, usually, very
opaque, it became quite transparent when held in a particular direction
as regards the impinging ray.

Mr. Gourlay observed that the lecture opened out to himself, as well as
to other vistas, which they had never dreamt of before.

--_Amrita Bazar Patrika_, 31-1-1913.

PROFESSOR J. C. BOSE AT LAHORE

LECTURE ON ELECTRIC RADIATION

A crowded assembly met at the University Hall, on the 22nd February,
1913, to hear the first of Prof. Bose's discourses before the University
of Lahore.

Dr. Bose opened his address by alluding to the historic journey