Feb. 19, 1880] 



NATURE 



385 



(lie sun give results comparable with each other, wall-screens give 

 results which are not comparable, inter sc, it being perhaps im- 

 possible to find two wall-screens in positions tolerably comparable. 

 But it is in investigating the daily range and sudden changes of 

 temperature, the humidity of the air, and others of the prime 

 factors of climate that wall-screens as instruments of observation 

 totally break down. 



A I'Ai'ER of researches on the rainfall of Austria-Hungary has 

 been recently presented to the Vienna Academy by Dr. Hann. 

 His object is, while showing the main features of distribution 

 of rain in the country, to establish a rational method of deduction 

 of results from measurements of rainfall during short intervals of 

 time. In the greater part of Austria-Hungary, he shows that June 

 is the most rainy month ; it is so in the whole of Bohemia and 

 Hungary, with Siebenbiirgen, in the eastern part of Galicia, and 

 in Bukowina. In Moravia and Silesia nearly the same rain falls 

 in June and August, with an intermediate decrease in July. 

 West Galicia and the Tatra-region show a preponderance of July 

 rain. Southwards from the Upper Dranthal a maximum in 

 October becomes predominant. From about 45° lat. southwards 

 more rain falls in the three winter than in the three summer 

 months. The further south the more pronounced is the distinc- 

 tion of a dry from a wet period. The dryest months in the whole 

 of Austria-Hungary drjwn to 45° (where July is the driest month) 

 are January and February ; and especially notable is the little 

 rainfall of February at the southern base of the central chain of 

 the Alps. 



PHYSICAL NOTES 



Measurements of the heat conductivity of iron hitherto 

 have given rather discordant results. This must be due, accord- 

 ing to Herr G. Kirchhoff and Heir Hansemann, to the fact that 

 in most of them the quantities of heat given out or received from 

 without by the body examined have not been sufficiently taken 

 into account. These physicists have recently described to the 

 Berlin Academy experiments by a method in which a cubical 

 iron mass, after being left to itself a long time, had a strong 

 water-spray directed against one of its side surfaces, the water 

 being some degrees hotter (or colder) than the place of observa- 

 tion. At several points back from the heated surface vertical 

 passages were made, each to receive one junction of a thermo- 

 pile of thin German silver and copper wire, the other junction 

 being at constant temperature. An observer, with the aid of a 

 chronograph, marked the point of time at which certain divisions 

 of the scale of the (mirror) galvanometer passed the vertical wire 

 of the telescope, at the same time dictating their number to an 

 assistant. Referring to the memoir for further details, we note 

 the conclusion arrived at, viz., that the heat-conductivity of iron 

 divided by the product of its specific heat and its density, at the 

 temperature 9 = 16-94 - °'°34 (0 - IS), when the temperature 

 is measured in centigrade degrees, and the units of time and 

 length are seconds and millimetres. With this result, that of 

 H. Weber agrees best ; he obtained the number i6'97for 39° C. 

 The results of F. Neumann, Angstrom, and Forbes, on the other 

 hand, are more divergent. (The substance used in the experi- 

 ments here described was Dortmund puddled steel, containing 

 0129 per cent, carbon and o - oSo silicium.) 



Herr E. Wiedemann has recently made further experiments 

 on the phosphorescent or fluorescent light produced by electric 

 discharges [IVu-J. Ann., No. 1). Nearly all platino-cyanide 

 double salts show fluorescence under the discharge ; but, so long 

 as they were undecomposed, no double fluorescence was observed, 

 When platino-barium cyanide had been traversed by a single dis- 

 charge, the strong green fluorescent light showed no dichroism, 

 but, after a series of discharges, dichroism appeared. It also 

 occurred when the crystals of that or other platino-cyanide 

 double salts were left a long time in vacuo (without electric dis- 

 cbarge), whereby they lost water ; and the more rapid appear- 

 ance of dichroism under the electric discharges is attributed to 

 heating of the crystals. Herr Wiedemann opposes Mr. Crookes's 

 view, offering the following proof of its incorrectness : — If the 

 positive current of a Holtz machine be sent through a very thick- 

 walled discharge-tube, and the discharges be made to follow one 

 another in such a rhythm that they are deflected from their course 

 in the tube by the finger, only a weak phosphorescent light appears 

 on the inner side of the tube, but a very bright green light 

 appears on the outer side. The non-observation of this before 

 is probably due to the thinness of the tubes commonly used. In 



narrow, and especially capillary tubes, too, only the inner wall 

 becomes luminous. 



We take the following from the New York Nation : — "It is 

 impossible for the unaided ear to determine with certainty the 

 direction of a distant sound, especially when the atmosphere is 

 foggy ; hence the great utility to navigators of the instrument 

 which its inventor, Prof. Alfred M. Mayer, of the Stevens Insti- 

 tute, has felicitously named the ' topophone,' or sound-placer. 

 It consists of ' a vertical rod passing through the roof of the deck- 

 cabin,' and bearing on the upper end 'a horizontal bar carrying 

 two adjustable resonators,' below which a pointer is set at right 

 angles with the bar. Rubber tubes from the resonators pass 

 through the roof of the cabin and unite in a single pipe connected 

 with a pair of ear-tubes. The vertical rod is turned by means 

 of a handle in any direction. The first step is to tune the 

 resonators accurately to the pitch of the sound under observation, 

 and fix them ' at a distance from each other somewhat less than 

 the length of the wave of that sound ; ' the next, by turning the 

 handle, to bring them simultaneously on the wave-surface, when, 

 as 'they both receive, at the same instant, the same phase of 

 vibration on the planes of their mouths,' it will result that if the 

 connecting tubes be of the same length, the sound-pulses, acting 

 together, will be reinforced to the ear, but if the tubes differ in 

 length by one-half the wave-length of the sound, the pulses will 

 oppose and neutralise each other, and thus tend to produce 

 silence. At this moment the horizontal bar is a chord in the 

 spherical wave-surface of which say the fog-horn is the centre ; 

 and the pointer represents a radius, 'or, in other words, coin- 

 cides in alignment with a line drawn from the place where the 

 sound is produced through the place of observation.' By sailing 

 the ship a measured distance 'at an observed angle from the 

 radius line thus found, a second radius line may in like manner be 

 found, 'and ' the distance between the two points of observation is 

 the base-line of a triangle, of which the two convergent radii are 

 the sides.' From these data the distance of the fog-horn is 

 readily computed." 



GEOGRAPHICAL NOTES 



The Vega reached Naples at 1.30 p.m. on Saturday, the 

 14th. Prof. Nordenskjold and his staff received a warm re- 

 ception from representatives of the Italian and Swedish Govern- 

 ments. Prof. Nordenskjold has been made Grand Officer, 

 and Lieut. Palander Commander of the Order of the Crown 

 of Italy. On Monday the explorers were entertained at a 

 grand banquet. The French Institute will hold its annual 

 meeting on March I, under the presidency of M. Daubrce, ulu 

 will deliver an inauguial address, the subject being Prof. 

 Nordenskjbld's expedition. It is expected that the professor 

 will land in France on that day. He will stop at Marseilles 

 and Lyons, where he will be received by the local geographical 

 societies and authorities. The Paris Geographical Society w ill 

 send a delegation to Marseilles. Prof. Nordenskjold will 

 receive the gold medal of the Society at Paris, in the large hall 

 of the Sorbonne. The several learned societies of Paris will 

 send delegations to witness this ceremony, which will be followed 

 by a grand banquet on the succeeding day. It is expected that 

 Prof. Nordenskjold will reach London in about a month's time, 

 but his present intention is not to give a public addre-s. He 

 does not feel himself sufficiently master of English for this 

 purpose, and, moreover, as might he surmised, he has an aversion 

 to 'starring." The botanists and zoologists of the expedition 

 will go overland, visiting all the museums with Arctic collections, 

 and will rejoin the Vega at Copenhagen. 



At the last promotion of the Legion of Honour M. Levasseur, 

 vice-president of the Paris Geographical Society, was appointed 

 to the grade of officer for his geographical and statistical works. 

 M. Levasseur is the editor of the statistical department of the 

 Annuaire of the Bureau des Longitudes, which lias been so much 

 enlarged recently. 



The French Chambers, at the instigation of M. ile Freycinet, 

 have voted a sum of 600,000 fr. for the cost of sending exploring 

 missions into the remoter parts of Algiers and Senegal, and 

 penetrating into the Sahara of the Western Soudan. Their im- 

 mediate object is to trace the lines of future railways, but the 

 indirect influence on the extension of our geographical know- 

 ledge is most important. Three scientific expeditions are being 

 organised in Algiers ; one is to operate in the Algerian Sahara, 

 and will not pass El Golea ; a second, comprising a corps of 



