[August, 
582 Proceedings of Societies. 
that in the narrow one. The experiments are being continued, 
and Mr. Clark’s other results will be communicated to the Society 
later on. 
June 28. — Prof. W. G. Adams in the chair. 
Prof. W. G. Adams, the President, exhibited his new 
measuring polariscope. It consists of three principal parts. 
The lower sedtion consists of a mirror, a lens, a Nicol’s prism, 
and two other lenses. The upper sedtion consists of lenses and 
Nicol’s prism arranged in the reverse order. Each lens and 
Nicol’s prism is supported separately by screws, and its position 
can be altered independently of the others. These two parts 
form a complete polariscope. Besides these there is a middle 
piece, consisting of two lenses (nearly hemispheres), forming a 
box to enclose the crystal immersed in oil, their curved surfaces 
being concentric. The whole middle piece is supported on the 
tubes of the upper and lower portions, and may be turned about 
the optical axis of the instrument. The vertical graduated circle 
carrying the central lenses and crystal may be turned through an 
angle about its horizontal axis. By means of an arc fastened 
perpendicularly on the graduated circle, with its centre at the 
centre of curvature of the central lenses, the crystal may be 
turned about another horizontal axis at right angles to the former, 
so that the crystal and the central lenses can be turned about 
each by three axes which are mutually at right angles. By 
means of a system of toothed wheels in gear with the rims of the 
central lenses, the crystal and central lenses may be turned sepa- 
rately about the optical axis of the instrument, so as to bring the 
planes of the optic axes of a biaxial crystal parallel to the plane 
of the vertical graduated circle. 
Sir John Conroy, Bart., read a paper “ On the Distribution of 
Heat in the Spedtrum.” After referring to Dr. J. W. Draper’s 
supposition that all the rays in the spedtrum have the same 
heating effedt, and to his statement that owing to the unequal 
dispersion of the prism for rays of different refrangibility the 
method that has been usual for determining the calorific intensity 
of the various parts of the spedtrum is an essentially defedtive 
one, the author described a graphical method for eliminating the 
effedt of the unequal dispersion of the prisms, and showed that 
from MM. Fizeau and Foucault’s reassurements, and also from 
those of Lamansky and Prof. Tyndall, that the maximum in- 
tensity is about the middle of the visible spedtrum and not at the 
red end ; and, further, that the curves given by various observers 
as representing the intensity of the heat in different portions of 
the spedtrum are, in reality, the “ dispersion curves” for the par- 
ticular prisms employed. 
Captain Abney, R.E., called attention to his published paper 
“ On the Measurement of the so-called Thermo-Spedtrum,” 
wherein he shows that the distribution of heat in the spedtrum 
