106 
POPULAR SCIENCE REVIEW. 
tone is gradually raised. According to the stroboscopic principle the bands 
look distinct and at rest where there pass before the eye an equal number of 
them and of slits in the disc. If a scale of numbers of vibration be attached 
to the cylinder, the number of vibrations of the syren can be at once ascer- 
tained by observing the part corresponding to the distinct and still ring of 
the cylinder. One sees, however, distinct and at rest, not only the part of 
the cylinder corresponding to the number of vibrations of the syren, but also 
all those parts which correspond to the harmonic over tones. Of all such 
parts it is, of course, that one which furnishes the smallest number of vibra- 
tions that corresponds to the vibration-number of the syren. (The author 
gives further details of the apparatus.) The determination may be varied 
in accuracy by varying the bands on the paper of the rotating cylinder. The 
apparatus may be applied to other sounding bodies. Thus, let a mono-chord 
string be stretched at right angles to the axis of the cylinder ; then simple 
teeth (Zachen) appear where the sounding string is opposite that part of the 
cylinder indicating the same number of vibrations. Another application is 
to attach small mirrors to tuning-forks, and watch in them the image of the 
rotating cylinder. An organ-pipe may be also submitted to observation 
with aid of Konig’s capsules and dancing jets. 
A New Society in London for the Study of Physics . — A preliminary meeting 
was held on Saturday, November 29th, 1873, in the Physical Laboratory of 
the Science Schools, South Kensington, to consider the formation of a 
Physical Society. The chair was taken by Dr. J. H. Gladstone, F.R.S, 
Thirty-six gentlemen were present, including most of the Physicists of 
London. It was resolved that the following gentlemen be requested to 
serve as an organising Committee : — W. G. Adams, E. Atkinson, W. Crookes, 
A. Dupr6, G. C. Foster, J. H. Gladstone, T. M. Goodeve, F. Guthrie, 0. 
Henrici. B. Loewy, Dr. Mills, A. W. Remold, and H. Sprengel. A letter 
was read from the Lords of the Committee of Council on Education, grant- 
ing the use of the Physical Laboratory and Apparatus at the Science 
Schools, South Kensington, for the purposes of the Society. 
ZOOLOGY AND COMPARATIVE ANATOMY. 
Further Researches on the Spectrum of the Plantain- Eaters. — The researches 
of Mr. Church which were carried out some years since (and who was kind 
enough to send us some of the feathers at the time) have been recently con- 
firmed by the discovery of Mr. J. Monteiro, who has found these birds, the 
Plantain Eaters, in great quantity in the neighbourhood of Sierra Leone. He 
says (“ Chemical News,” October 17) that “ these lovely birds are common on 
the West Coast of Africa, and on that part of it that I am well acquainted 
with, viz., from Loango, in 5° S. lat., to Little Fish Bay, in 15° S. lat., their 
loud and prolonged cry is to be frequently heard in the thick forest, where they 
find their fruit food most plentifully. Over the whole of the country I have 
mentioned, and for a considerable distance inland, copper is found most abun- 
dantly distributed as malachite, or green carbonate ; in fact, specks and indica- 
tions of the green mineral are to be noticed almost everywhere. Whether 
