2l8 



NATURE 



\yan. 13, 1876 



The Revw Scientifique announces the death of the naturalist 

 M. Pictet. 



The Cologne Gazette states that Herr Heuglin, the African 

 traveller, has declined the offer of the Khedive to take the com- 

 mand of the troops sent to Abyssinia, in place of the late 

 Munzinger Pasha, but is organising an Abyssinian exploration 

 for scientific purposes. 



Dr. von Richthofen, the well-known traveller and geo- 

 grapher, has been appointed Professor of Geography at the Uni- 

 versity of Bonn. He is still occupied at Berlin vnth the editing 

 of his great work on China. 



The additions to the Zoological Society's Gardens during the 

 past week include a Le Vaillant's Cynictis {Cynictis penicillata) 

 from South Africa, presented by the Viscount Maudeville ; a 

 Hooper Swan {Cygnus ferus), European, presented by Mr. Mon- 

 tague Kingsford ; a Weeper Capuchin ( Cebus capucinus) from 

 Brazil, presented by Mr. August Kettner ; a Macaque Monkey 

 (Macacus cynomolgus) from India, presented by Mr. T. J. 

 Dunn ; two Darwin's Pucras [Pucrasia Darwini) from China, 

 purchased. 



SCIENTIFIC SERIALS 



Zeitschrift der Oesterreichischen Gesellschaft fur Meteorologie, 

 Nov. 15, 1875. — Dr. Billwiller, of Zurich, contributes an article 

 on a local occurrence of the northerly " Fohn." It was formerly 

 believed that the Fohn came from the Sahara Desert, whence it 

 derived its warmth and dryness, but Hann showed a few years 

 ago that, according to known physical laws, descending air 

 becomes warmer and drier, that winds of the Fohn kind are not 

 confined to the Alps but occur in other mountainous regions, 

 and that the southern slopes of the Alps have a north wind, 

 which is the exact counterpart of that called the Fohn. A mass 

 of observations made in Switzerland have since proved the cor- 

 rectness of his theory. Herr Billwiller, from the data he has as 

 yet examined, finds that isolated Fohn winds prevail only when 

 a broad current flows over the whole Alps in the same direction, 

 ascending on one side and descending on the other. But there 

 are cases in which no perceptible upward movement can be 

 traced on one side, and yet on the other the Fohn descends into 

 the valleys from above. A difference of density, often great, is 

 the cause of this. The lower strata being obstructed the outflow 

 of air necessary to restore equilibrium comes from above. The 

 merely local Fohn blows strongly down a valley, but on reaching 

 the colder air of the plain mixes with it and quickly comes to 

 rest. Tables are given showing meteorological conditions in 

 particular cases. — The next article, written by Dr. Wild, and 

 quoted here from the Annual Report of the Imperial Observatory 

 at St. Petersburg, is a review of the work of the Meteorological 

 Congresses of 1873 and 1874. Perhaps the most important 

 result of these congresses will be the general use of more trust- 

 worthy instruments by official and private observers. The fol- 

 lowing advantages have already been gained : an international 

 system of ciphers for telegraphic despatches throughout nearly 

 the whole of Europe ; an international form of publication in 

 the following countries : Norway, Sweden, Denmark, Russia, 

 Austria, Switzerland, Italy, and part of Germany ; and lastly, 

 the establishment in many States of central institutions. We 

 shall thus obtain better, more uniform, and more accessible data 

 as a consequence of the late congresses. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, Jan. 6. — On the refraction of sound by the 

 atmosphere, by Prof. Osborne Reynolds, Owens College, Man- 

 chester. Communicated by Prof. Stokes, Sec. R.S. 



This paper may be said to consist of two divisions. The first 

 contains an account of some experiments and observations under- 

 taken with a view to ascertain how far the refraction of sound 

 caused by the upward variation of temperature may be the cause 

 of the difference in the distances to which sounds of the same 

 intensity may be heard at different times. 



Some rockets, capable of rising 1,000 feet, and then exploding 

 a cartridge containing 12 oz. of powder, having been procured. 



an effort was made to compare the distance at which the rockets 

 could be heard with that at which a gun, firing k lb. of powder 

 and making a louder report than the rockets, could be heard 

 under the same conditions of the atmosphere. In the first in- 

 stance the rockets and the gun were fired from a spot in Suffolk, 

 around which the country is tolerably flat, observers being sta- 

 tioned at different distances. Owing, however, to the effect of 

 the wind and the time required for the observers to proceed to 

 the distant stations, these experiments were not successful in 

 establishing the comparative merits of the gun and the rockets. 

 They were, however, important as showing that on hot calm 

 days in July the reports of the rockets never failed to be dis- 

 tinctly audible at distances of four and five miles, although the 

 sun at the time was shining with full force on the ground, and 

 rendering the air near the surface so heterogeneous that distant 

 objects seen through it appeared to wave about and twinkle. 



The next attempt was made during a cruise on the east coast. 

 After three weeks cold and windy weather, the 19th of August 

 was a fine day, and some experiments were made in Lynn Deeps, 

 which revealed a very extraordinary state of the atmosphere as 

 regards the transmission of sound. A party rowed away from 

 the yacht in one of her boats, it having been arranged before- 

 hand that either a rocket or a large pistol was to be fired from 

 the yacht when signalled for ; also that when those on the yacht 

 heard those in the boat call they should answer. The boat pro- 

 ceeded to a distance of five miles, until those on the yacht had 

 completely lost sight of it ; but all the time the calls from the 

 boat were distinctly heard by those on the yacht, although after 

 they had lost sight of the boat they ceased to answer the calls. 

 On the boat also not only were the reports of the pistol and 

 rockets distinctly heard, but every answer from the yacht was 

 heard plainly. The last came after an interval of thirty-five 

 seconds, which gave the distance 34 miles. Nor was this all ; 

 but guns, and on one occasion the barking of a dog, on the 

 shore eight miles distant, were distinctly heard, as were also the 

 paddles of a steamer fifteen miles distant. 



The day was perfectly calm, there was no wind, the sky was 

 quite clear, and the sun shining with great power — conditions 

 which have been described as most favourable to the stoppage of 

 the sound by the heterogeneity of the atmosphere, and which 

 may also be described as most favourable for great upward re- 

 fraction. On this day, however, it was observed that all the 

 time distant objects loomed considerably, ue., appeared lifted. 

 This showed that the air was colder near the surface of the sea 

 than it was above. It is to this circumstance that the extraordi- 

 nary distances to which sounds were heard on this day is sup- 

 posed to be due. The diminution in the temperature of the air 

 being downwards, the sound, instead of being lifted as it usually 

 is, was brought down, and thus intensified at the surface of the 

 water, which, being perfectly smooth, was thus converted into a 

 sort of whispering-gallery. 



The report of the pistol and the sounds of the voice were at- 

 tended with echoes, but not so the reports of the rockets ; and 

 it is suggested that these so-called echoes may be found only to 

 attend sounds having a greater intensity in one direction than in 

 another. 



The second part of the paper refers to a phenomenon noticed 

 by Arago in his report of the celebrated experiments on the 

 velocity of sound made on the nights of the 21st and 22nd of 

 June, 1822. 



It was then found that, although the guns fired at Montlhery 

 could be distinctly heard at Villejuif (eleven miles distant), those 

 fired at Villejuif could not be heard at Montlhery without great 

 attention, and at times (particularly on the second night) they 

 were not heard at all ; although on both nights the wind was 

 blowing from Villejuif to Montlhery, the speed of the wind, 

 which was very light, being about i foot per second. No expla- 

 nation of this phenomenon was offered by the observers, although 

 it was much commented on. And on the second night the gun 

 at Villejuif, which on the previous night had been pointed 

 upward, was brought down in the hope that this might improve 

 its audibility (this step was, however, found to render matters 

 worse than before). 



From this lowering of the gun at Villejuif it seemed as though 

 there was probably some difference in the conditions under which 

 the guns at the two stations were placed, as if that at Villejuif 

 was fired from a level, while that at Montlhery might be fired 

 over a parapet. An inspection of the district confirmed this 

 view ; for Villejuif is on a low, flat hill, while Montlhery is on 

 the top of a steep cone ; and not only is it 80 feet above Ville- 

 juif, but it is surmounted by the mound of an old castle, which 



