On a Simple Method of Extending the Bolmer Series of Hydrogen in a Vacuum Tube. R. WHIDDINGTON. (Phil. ~ag., Oct., I923.)--in an ordinary vacuum tube it is difficult to get more than four lines of the primary spectrum of hydrogen. In contrast to this is the completeness of the series in starlight. By using a hot tungsten cathode in hydrogen at a pressure of about .ooi mm. of mercury, at least nineteen members of the series were obtained.
G. F. S. The Scattering of Light by Liquid Droplets and the Theory of Coronas, Glories and Iridescent Clouds. BmI~UBI~USAN RAY. (Proc. Indian Asso. Cult,iv. $ci., 8, Pt. I, i923.)--In certain fields of science the investigator can carry on his work far from the maddening crowd and in lake and stream under the open sky. Such experiences are rather rare in physics though by no means unknown. The magnetic survey of the earth conducted by L. A. Bauer, the phenomena discussed in Humphreys' " Physics of the Air," in Arrhenius' " Cosmic Physics," and in the brochure of Freiherr yon und zu Aufsess on " Die Physikalischen Eigenschaften der Seen," all these have taken the physicist away from his laboratory and have made of him for the time a passive observer of what he cannot control and manipulate..So it is with the subject of this paper.
" G. C. Simpson has advanced the very interesting theory that the iridescent borders and irregular patches of colour occasionally shown by thin high clouds some I5 ° or 3 °0 from the sun or more are only fragments of coronas formed by exceedingly small undercooled droplets of very approximately uniform size." To test this clouds were formed in a flask by the adiabatic expansion of air saturated with water vapor. The largest drops had a radius of about .oo8 mm. and the smallest of .ooI 5 mm. The light from a IOOO c.p. tungsten lamp was focussed upon the centre of the flask. " If observations are made in a direction nearly parallel to the direction of light, the eye being placed on the side opposite to that at which the source of light is situated, one can see vivid patches of colour in the track of the beam, red and green being the most prominent tints. If the droplets are large, these coloured patches can only be seen in directions embraced within a small solid angle, but as the size decreases, they become visible at larger and larger angles. With very thin clouds consisting of small droplets, the coloured patches could be seen even at a large angle (3 °° to 4o°). The observations thus lend an experimental support to Simpson's suggestion about the formation of the iridescent clouds."
From the results of additional experiments, the author is led to reject Humphreys' explanation of glories as akin to coronas, the scattered light being that reflected from the deeper parts of the cloud on which the phenomenon is seen. The effect is ascribed to the scattering of sunlight at the surface of the cloud.
This paper is a manifestation of the interest felt in British India in the Tyndall Effect and kindred optical phenomena.