Jtme 17, 1880] 



NA TURE 



157 



it is Herr Exner, or all the authorities on thermo-electricity from 

 Seebeck to Tait, on whom we are to rely for the facts. 



In a new capillary electrometer described by M. Debrun in 

 the Journal dc Physique (May), the microscope is dispensed 

 w ith, and the requisite sensibility obtained by inclining the tube, 

 which is slightly conical. The capillary tube is bent into a 

 somewhat zig-zag shape, the two turned-up ends opening into 

 larger tubes, and with tlie mercury in these wires are connected. 

 Tlie support can be turned in a vertical plane, so as to give the 

 middle part of the capillary tube any desired inclination. 



M. Crova commends, for photometric purposes (Journal de 

 Physique, May), M. Prazmowski's polariser, \\hich is a Nicol, 

 with faces normal to the axis of the prism, the two halves of 

 which are joined with linseed oil. It requires large pieces of 

 spar, and the joining is long and difficult, but there are several 

 advantages. Thus the layer of oil (unlike Canada balsam), 

 causes hardly any loss of light ; its index, i ■4S5, being nearly 

 equal to the extraordinary index of spar, the polarised field is 

 limited on one side, as in Nicjls, where the total reflection of the 

 ordinary ray commences, by a red band ; but these cond limit, 

 corresponding to total reflection of the extraordinary ray, is 

 tlirown out of the field of vision ; the angular value of the 

 polarised field is thus increased. The increase of field, the 

 angular separation of the only coloured band, and the direction 

 of its bases, normal to the axis, are qualities to be appreciated in 

 certain cases. 



According to some recent experiments of M. Goulier, the 

 coefficient of expansion by heat of a metal is independent of any 

 pressure put upon the metal, and is the same under a stress of 

 traction as under one of compression. 



Mr. W. p. Johnson gives an account in the Philosophical 

 Magazine of a new use of the telephone. It is sometimes neces- 

 sary to grapple aud lift a faulty cable, and if it lies in the water 

 along with other cables of similar exterior make it has hitherto 

 been impossible to decide, .without cutting it apart, on the 

 identity of the grappled portion. To avoid the obvious evil of 

 having to cut and splice the cable unnecessarily, it is now sug- 

 ge-ted to employ the telephone on an auxiliary parallel wire in 

 which the induction may be sufficiently strong to enable the elec- 

 tricians in charge to read the signals which may be sent into the 

 cable, and so identify it. 



The following pretty experiment, devised by Mr. R. H. 

 Ridout, illustrates the surface tension of mercury. A shallow 

 tray, six inches by three, is supported on three levelling screws, 

 and inclined just so th.at the mercur)' does not flow over the 

 lipped edge. If now a small quantity of the liquid be set flowing 

 over the edge it Mill draw the rest of the liquid over with a 

 siphon-like action. It is difficult, however, to get the surface so 

 clean that no adherent trail shovild be left, marring the comple- 

 tion of the experiment. 



The expansion of glass by heat may be demonstrated as 

 follows : — A glass tube of narrow bore and about eighteen inches 

 long is bent round in the shape of a horse-shoe, so that the free 

 cuds are within a millimetre of one another. Between these ends a 

 coin may be held, being nipped between the ends of the rod and 

 held there by the grasp due to the elasticity of the glass. If 

 now the outer portion of the curved part be warmed, the ends 

 open slightly and the coin drops out. This experiment is also 

 due to the ingenuity of Mr. Ridout. 



The phenomenon lately discovered by Hall of the action of a 

 magnet in altering the path of a current of electricity in the 

 conductor which carries it, has formed the starting-point for two 

 investigations, which have appeared separately in the IViemr 

 A7!zeiger, by Bjllzmann and von Ettingshausen respectively, in 

 which they point out that this discovery may be applied to 

 determine the absolute velocity of electricity in a conductor. 



M. LOUGHININ has published in the last fascicule of the 

 Journal of the Russian Physical aud Chemical Society (vol. xii., 

 f.xsc. 4) a note on his important work on the heat which results 

 from tl-.e burning of several alcohols. The substances experi- 

 mented on are burnt in a jet of oxygen in a glass vessel which 

 is placed in the water of a calorimeter. The figures are : For 

 normal propylic alcohol, 481 '6 calories for one molecule; iso- 

 propylic alcohol, 479 calories ; isobutylic alcohol, 638"6 calories. 



GEOGRAPHICAL NOTES 



Mr. Carl Bock has lately returned to London after his 



journeys in Borneo, bringing with him a magnificent series of 



portraits of tlie native tribes of that island, — both Dyaks and 

 forest people — taken in water colours. These, we under.-tand, 

 are to be reproduced, at the expense of the Dutch Government, 

 by chromolithography, and will illustrate his report on the 

 journey, which is to be read in the first instance before the 

 Royal Geographical and Anthropological Society of Holland. 

 Pending the publication of this report, Mr. Bock refrains, at the 

 desire of the Dutch Government, from anticipating it in England 

 even by a preliminary sketch. The varieties of type, the 

 methods of adornment, the manner, and to some extent the 

 religion of these distinct races, are all brought out in Mr. Bock's 

 faithful drawings taken from the life on the spot, which form, 

 over and above the objects for which the journey was taken, a 

 splendid contribution to ethnography, the publication of which 

 will be looked forward to with interest ; the greater perhaps if 

 Mr. Bock were permitted to give some further slight outline than 

 has already appeared in the pages of Nature. Mr. Bock has 

 also made an extensive collection of the swords, lances, blowing 

 tubes, and shields (some of the latter covered with human hair), 

 which are used by the natives. He seems to have had the happy 

 knack of making friends of the savages ^^ horn others have found 

 murderers, and has brought himself back alive to receive the 

 honour that is his due. 



The current number of the Geographical Society's Proceedings 

 opens with the Rev. C. Maples' very interesting paper on Masasi 

 and the Rovuina district between Lake Nyassa and the east 

 coast of Africa. The Rev. C. T. Wilson's and Mr. Felkin's 

 brief notes on L'ganda and the journey through the Nile region 

 are also published, and are followed by an account of that rare 

 occurrence in Dominica, a volcanic eruption at the Grand 

 Souffriere, which took place on Januaiy 4. The geogi-aphical 

 notes include a list of latitudes in Central South Africa, Mr. 

 F. C. Selous' explorations on the Zambesi, &c. (of which full 

 accounts are to be published in a later number), and a journey in 

 Damara-land and beyond the River Okavango. An allusion is 

 also made to Mr. Whymper's ascent of Cotopaxi, and to a 

 proposed exploration of some of the unknown affluents of the 

 Puvus. Among the remaining notes is a long account of the 

 country of the Mijjertain Somalis, and of recent exploration in 

 Central Australia. Col. H. Yule furnishes an obituary notice of 

 General Macleod, whose pioneer journey into the interior of the 

 Indo-Chinese Peninsula in 1S36-7 is, we fear, now almost 

 forgotten. The map this month is that of the central portion of 

 South Africa, illustrating Dr. Emil Holub's journeys, and con- 

 structed in part from his original drawings. 



Dr. Emil Eessels, who was with Hall in the Polaris, hopes 

 to undertake a new Arctic expedition in iSSi on funds sub- 

 scribed in America. He will establish a station at the entrance of 

 Jones Sound, where a scientific staff will be located, consisting 

 of an astronomer, a physicist, a geologist, botanist, and zoologist. 

 Intercourse will be kept up with the settlement of North Green- 

 land by means of a yacht, as well as with the whalers. 



SiGXOR Cristoforo Negri, President of -the Italian Geo- 

 graphical Society, and member of the Geographical Society of 

 Loudon, has just published an interesting pamphlet at Genoa, in 

 which he warmly advocates the proposed Italian Antarctic 

 expedition. He demonstrates the importance not only to science, 

 but probably also to trade, of such an expedition. A special 

 circumstance increases the desirability of this Italian Antarctic 

 expedition. In 1882 the transit of Venus will again occur, but 

 after that not again for a hundred years. The Italian expedi- 

 tion, therefore, finding itself in 1 882 at some point of the 

 Antarctic circle, would be able to observe this phenomenon 

 under favourable conditions. Signor Negri believes that the 

 expedition might be made with a single vessel at no very 

 extravagant cost, perhaps 600,000 to 700,000 Italian lire. It 

 would spend two winters, returning to La Plata, if necessary, 

 during that period, to re-provision and re-coal the ship. 



At the last meeting of the Russian Geographical Society the 

 Secretary intimated that M. Potanin continues his exploration of 

 North- Western Jlongolia. The Society has just received from 

 him a part of his collections, and expects soon to receive his 

 detailed report. M. Tiaghin, who stays on Novaya Zemlya for 

 the exploration of that island, has brought together a very good 

 collection of plants, and has made interesting communications 

 as to the geography of the island. As to new expeditions, 

 the Society proposes to send M. Mereshkovsky to the Crimea for 

 ethnographical and archceological explorations, and M. MalakhofT 

 to the Middle Ural Mountains for zoo-geographical investiga- 



