262 



NA TURE 



[July 14, 1904 



strong- dark lines in Piscian stars, the effect may be pro- 

 duced because sun-spots are more numerous in such stars. 

 From the evidence adduced above it seems a far more 

 probable explanation to suppose that these lines are in- 

 tensified in sun-spots, and strengthened in those stars which 

 have been placed on lower temperature levels than the sun, 

 because the general temperature conditions are similar. 

 That is to say, the fall of temperature experienced by the 

 metallic vapours in passing from the photosphere to the 

 spot nucleus is of the same order as that to which an 

 absorbing atmosphere is subjected in passing from the 

 temperature conditions of Capella or the sun to those of 

 .Vcturus or the lower temperature stars. 



" .An Experiment Illustrating Harmonic Undertones." 

 By H. Knapman. Communicated by Dr. G. T. Burch 

 F.R.S. 



If a vibrating tuning-fork is pressed against a light 

 object such as a piece of paper or a stretched string, this 

 object may follow the vibrations of the fork, contact being 

 continuous. This use of a tuning-fork is mentioned in 

 Lord Rayleigh's " Theory of Sound," § 133. In the present 

 experiment a lightly poised piece of paper is touched by 

 the fork ; with small pressure contact may be broken during 

 part of each vibration, and the paper gives a note re- 

 sembling that of a bowed violin-string, in which harmonic 

 overtones are strong. With still less pressure, contact may 

 be made only at every other vibration of the fork, when 

 the paper gives a note an octave below that of the fork. 

 Similarly, contact at every third vibration of the fork gives 

 the twelfth below, and so on. We thus have the series of 

 harmonic undertones, and with a c" fork ten or more may 

 be made easily audible. 



An optical method of examining the vibrations is also 

 described. A large tuning-fork was made to touch a small 

 card, the edge of which was observed with a lens against 

 a dark background, and appeared to be drawn out into a 

 continuously shaded band, in which stationary positions 

 were visible. The characteristics of various states of 

 vibration were readily perceived. 



Geological Society, June 22.— Dr. J. E. Marr, F.R.S., 

 president, in the chair. — The igneous rocks of Pontesford 

 Hill (Shropshire) : Prof. W. S. Boulton. The hill is a 

 " plagioclinal ridge," bounded on all sides by faults; it 

 is made up entirely of igneous rocks. There are two distinct 

 groups of igneous rocks : a bedded group, consisting of 

 rhyolites and acid tuffs, with andesites and andesitic tuffs, 

 and an intrusive group of olivine-dolerites. The northern 

 end of the hill consists of rhyolite. The andesitic group is 

 made up of felsitic-looking tuffs, passing up into andesitic 

 tuffs, halleflintas, and lavas. The intrusive rocks are basic 

 and often amygdaloidal ; they compare in composition with 

 such olivine-dolerites as those of Rowley, the Clee Hills, and 

 Little Wenlock. — The Tertiary fossils of Somaliland, as re- 

 presented in the British Museum (Natural History) : 

 R. B. Newrton. The new material described is that in 

 the Donaldson-Smith collection, and one presented by Major 

 R. G. Edwards Leckie. The large Lucinida; and speci- 

 mens of Campanile (previously considered as Nerina;a) are 

 typical of Eocene rocks generally, and they agree with the 

 Foraminifera in the Somaliland Limestones in supporting 

 the reference of these rocks to this period. Two limestones 

 seem to be represented in the collections, and appear to be 

 capable of correlation with those of the south-eastern corner 

 of Arabia, as well as with those of Sind and Cutch. Six 

 new species are described and named, and sixteen species 

 or varieties described. — The Caernarvon earthquake of June 

 19, 1903, and its accessory shocks : Dr. C. Davison. This 

 earthquake was the strongest disturbance indigenous to the 

 county for more than five centuries. Its disturbed area 

 contained about 25,000 square miles. The centre of the 

 innermost isoseismal (intensity 7) was situated beneath the 

 sea, about 4 miles west of Pen-y-groes, and the longer a.xis 

 of the isoseismal ran from N. 40° E. to S. 40° W. It is 

 concluded that the earthquake was caused by a slip of about 

 16 miles in length along a fault running in the above 

 direction, hading north-westward, and passing either 

 through Clynnog or a mile or two either to the north-west 

 or south-east. 



NO. 181 I, VOL. 70] 



Challenger Society, June 29.— Sir Jchn Murray in the 

 chair. — The Chairman exhibited the skeleton of ai 

 problematical organism, possibly allied to Heliopora, from 

 the sea bottom off Cuba, and read a letter on its structure 

 from the late Prof. Alleyne Nicholson. — Mr. E. W. L. 

 Holt e.xhibited some new and rare Crustacea from the 

 .■Atlantic. Mr. Holt also read a paper on the Schizopoda 

 of the North Atlantic and its eastern slope, from the 

 collections by Mr. George Murray in the Oceana, by Dr. 

 G. H. Fowler in H.M.S. Research in the Fjeroe Channel 

 and the Bay of Biscay, and by himself in the Helga oft 

 west Ireland. These collections included a number of 

 interesting novelties, notably among those forms which 

 appeared to live actually on the bottom in deep water, and 

 were caught by a tow-net attached to the trawl-rope. — 

 Mr. Stanley Gardiner opened a discussion on the distribu- 

 tion of marine larvK, in which, mainly from his own 

 observations, he dealt with their length of life in reference 

 to their populating banks and shores in the Indo-Pacific anct 

 Atlantic Oceans. He concluded that the larvae of Crustacea 

 and Echinoderms other than Crinoids may be expected to 

 reach almost any bank, but that results in geographical 

 distribution may be expected from Coelenterata and 

 Turbellaria, and to some degree also from Chaetopoda, 

 Gephyrea, and Mollusca. 



Edinburgh. 

 Royal Society, June 6. — The Hon. Lord M'Laren in the 

 chair. — An obituary notice of Dr. Charles Gatty, prepared 

 by Prof. W. C. M'Intosh, was read. — Dr. E. G. Coker, 

 McGill University, Montreal, communicated a paper on the 

 measurement of stress by thermal methods. The paper was 

 experimental, investigating on the one hand the effect of 

 tension upon the coefficient of thermal expansion, and on 

 the other the change of temperature accompanying the 

 application of various kinds of stress. The changes of 

 temperature were measured thermoelectrically, corrections 

 being applied for the loss of heat by conduction, radiation, 

 &c., as the stress was being applied. A number of 

 results were established, the most interesting being, 

 perhaps, the fact that the rate of heat production during 

 the development of the strain continues constant even after 

 the limit of elasticity has been exceeded, .^s regards the 

 effect of stress on the coefficient of expansion, it was found 

 that there was no appreciable change. — A paper was read 

 on the spectrum of Nova Persei and the structure of the 

 bands, as photographed at Glasgow, by Prof. Becker. In 

 the earlier photographs before August, 1901, the spectrum 

 suggested a number of bright bands fading towards the 

 ends and overlapping one another. In the later photographs 

 the bands become detached and suggest a line spectrum ir> 

 which the lines have broadened into bands. The broaden- 

 ing was found to be proportional to the wave-length, and 

 independent of the nature of the element. The sequence of 

 alternate maxima and minima which characterised the 

 bands, and the distances separating these, were found to 

 bs also proportional to the wave-length. This is in accord- 

 ance with Doppler's principle if we assume the effects to 

 be due to motion in the line of sight. An important part 

 of the paper was devoted to a mathematical demonstration, 

 of the correctness of the assumption that the resultant 

 intensity at any point of the plate where several bands are 

 superposed is the sum of the intensities which the radi- 

 ations would singly produce. The general conclusion was 

 that the spectrum was due to hydrogen and helium. — In a 

 note on astronomical seeing. Dr. Halm directed attention 

 to Langley's ingenious method for improving definition in 

 a telescope by agitating the air in the tube. This result, 

 at first sight so contradictory to all preconceived ideas, 

 suggests consideration as to the condition of the atmo- 

 sphere as a whole when the best definition is obtained. 

 The cause of the blurring is no doubt due to the changes 

 of refraction which accompany the movements of the air. 

 It every portion of the moving air came to its new position 

 with exactly the temperature and density which belong to 

 the new position, there would be no change of refraction 

 and consequently no blurring. Now this state is realised 

 when the air is in a condition of convective or adiabatic 

 equilibrium, and hence definition will be clearer the more 



