2o6 



NA TURE 



{July I, iSSo 



apparently executed with much care, and is stated to be the most 

 accurate of its kind yet produced in Brazil. He has also 

 published the first part of a work on the railways of Brazil in 

 1879, descri]itive of the lines shown on the above-mentioned 

 map, and he has added a skeleton map showing the railways 

 only. Dr. Passos ha<:, we believe, been induced to issue these 

 publications in order to make more widely known in England 

 the ptogre-s in railway communication now going on in Brazil, 

 a subject which is of considerable interest from an economical 

 and geographical point of view. 



The last Bulletin of the Antwerp Geographical Society con- 

 tains a geographical and commercial essay on the Australian 

 colonies, which is accompanied by reproductions of some curious 

 old maps, as well as by a sketch map which professes to dis- 

 tinguish the arable, pastoral, and desert regions of the continent, 

 in regard to which, however, the writer's information hardly 

 appears to be brought down to the latest date. 



From the Japan papers we learn that H.M.'s surveying vessel 

 Sylvia left Hiogo on April 24 for Cape Chichakoff to take a 

 line of soundings there, which will complete her surveying work 

 on the Japanese coast. The Sylvia has been employed for about 

 twelve years in surveying the coasts of Japan and the Inland Sea, 

 and during this period has done excellent service to navigation. 



M. DE UjF.VLVY is to leave Paris at the end of the summer on 

 his new journey of exploration in Central Asia. 



The Timis correspondent writes from Copenhagen that on 

 June 24 died there Mr. Carl Petersen, whose name is connected 

 with some of the most renowned Arctic explorations. He was a 

 born Dane, but had lived many years in Greenland, and had 

 there acquired a perfect knowledge of the Esquimaux language, 

 being at the same time a most skilled hunter and fisherman. At 

 the age of thirty-seven he was engaged by Capt. Penny as 

 interpreter, and accompanied his expedition in the years 1850-51. 

 Some years later he followed Dr. Kane on his unfortunate 

 expedition, when the vessel had to be left in the ice and the 

 crew were nearly starved and frozen to death. He had not been 

 home more than a couple of weeks after returning from a two 

 years' stay in Greenland, before he w cut out again as interpreter 

 with the Fox, Capt. Sir Leopold M'Clintock, with Mr. (now 

 Sir) Allan Young as sailing master. Of this expedition, lasting 

 from 1 85 7 to 1859, and leading to the discovery of the fate of 

 Sir John Franklin, he has written a graphic description, supplying 

 many details wanting in the well-known book of .SirL. M'Clintock, 

 and inscribed with the words chosen by Jane Franklin for the 

 flag of the Fox, " Hold fast," happening to be quite as correct in 

 Danish as in English. In 1861 he accompanied the .Swedish 

 naturalists Nordenskjold and Torell on their first expedition to 

 Spitzbergen, and when, in last April, the Vega passed Copen- 

 hagen, the hardy old sportsman and sailor, with his cross and 

 Arctic medal, was one of the friendly faces greeting the discoverer 

 of the North-East Passage. Mr. Petersen died from heart- 

 disease at the age of si.xty-seven. 



PHYSICAL NOTES 



One of our electrical contemporaries across the Channel gives 

 a glowing description of toie grande machine electriqiieallemande, 

 which its editor says he wishes to see introduced into France, 

 "where our official professors appear to have lost all ambition 

 at making things big." The great gooseberry of the season is 

 nothing to this new machine, which is, we are told, composed of 

 twenty parallel disks of 1,300 metres in radius. This is 

 "making things big" with a vengeance, for the diameter of the 

 disks will be over 2.^ kilometres, or about a mile and a half. 

 Did our contemporary make a double blunder when it wrote 

 " ireize cents metres"') If we remember rightly, the plates in 

 Topler's induction-machine, which appears to be the one 

 referred to, are not far from 13 centimetres radius. 



Professors Brackett and Young have made a new deter- 

 mination of the efficiency of Edison's dynamo-electric generator 

 and of his carbon horse-shoe Lamp, and find that one horse-power 

 applied at the dynanometer would produce in this lamp a light 

 equal to that of 107 stand.ard caiidles. As a matter of fact the 

 lamp was only giving a light of 107 candles while consuming 

 0'077 of a horse-power, w hich is not quite the same thing. 



Prof. Quincke has lately been occupied with a very remark- 

 able research on the alteration of volume which a dielectric 

 experiences under the stress of an electric charge. In most 



cases the result of surface electrification is to produce a minute 

 expansion, but one class of bodies — that of the fatly oils and 

 resins — contracts under similar circumstances. Herr Quincke 

 applies his measurements to explain the phenomena observed by 

 Kerr of the double refraction of light exhibited by dielectric 

 media when under electrostatic strain ; and he shoMS that the 

 optical effects in the two classes of media are opposite in 

 character. 



M. JIouchet is continuing in Algeria the researches on the 

 utilisation of solar heat which he began in the South of France. 

 He employs, according to his recent communication to the 

 Cotiiptes Reiidiis, a mirror 3'S metres in diameter to concentrate 

 the rays of the sun upon a boiler of copper 5 millims. thick. 

 Even on dull days the apparatus boils water under half an hour. 

 M. Mouchet has employed his apparatus for the distillation of 

 oils and essences, the boiling of linseed oil, and the sublimation 

 of benzoic acid. He has even succeeded in working a small 

 engine. 



Mr. G. R. Carey of Boston has published in tlie Scientific 

 American a suggested system for the transmission of light by 

 electricity. A camera throws an image of the object to be 

 exhibited upon a surface made up of small pieces of selenium, 

 each of which forms part of a separate voltaic circuit, the cir- 

 cuits passing to a receiving instrument, where they reproduce the 

 image by incandescence. To this Mr. Sawyer has appended the 

 following criticisms : — The action of light in altering the con- 

 ductivity of selenium is slow. To transmit satisfactorily an 

 image one inch square would require 10,000 selenium points and 

 10,000 conducting wires, unless some principle of isochronous 

 movement could be devised — which Jlr. Sawyer regards as 

 unattainable in practice. 



M. Faye has lately published in the Comptes RenJus a re- 

 markable paper on the physical forces whicli have produced the 

 present figure of the earth. After remarking on the use of the 

 pendulum in determining the figure of the eartlf from series of 

 measurements of the intensity and direction of the gravitation 

 force at different parts of tlie eartli's surface, he draws attention 

 to the curious fact that while the direction and intensity of gravity 

 are affected perceptibly by the presence of hills such as Schie- 

 hallion and Arthur's Seat, or even by masses as small as the 

 Great Pyramid of Gizeh, gigantic mountains such as the 

 Himalayas, and great elevated plateaux and table-lands do 

 not affect the pendulum-indications in any sensible manner, 

 except in certain cases where upon elevated continents 

 there appears to be a veritable defect of attraction in- 

 stead of the excess which might be expected. Indeed, 

 the observations are sufficiently striking to seem to point to 

 the supposition that not only under every great mountain, but 

 even under tlie whole of every large continent, there were 

 enormous cavities. More than this, tlie attraction at the surface 

 of all the great oceans appear too great to agree with the dis- 

 tribution presumed by Clairant's formula, w hich is exact enough 

 for most purposes. Sir G. Airy's suggestion that the base of the 

 Himalaya range reaches down into the denser liquid interior, 

 and there displaces a certain amount of that liquid, so that the 

 exterior attraction is thereby lessened, is one w-hich, inherently 

 improbable, fails to have any application in explaining why the 

 attraction above the seas should be greater than over the 

 continents. M. Faye propounds the following solution to the 

 difficulty : — Under the oceans the globe cools mors rapidly and to 

 a greater depth than /teneath the surface of the continents. At a 

 depth of 4,000 metres the ocean will still have a temperature not 

 remote from 0° C, while at a similar depth beneath the earth's 

 crust the temperature would be not far from 150° C. (allowing 

 33 metres in depth down for an increase of 1° in the internal 

 temperature). If the earth had but one uniform rate of cooling 

 all over it, it would be reasonable to assume that ,the solidified 

 crust would have the same thickness and the same average density 

 all over it. It is therefore argued that below the primitive 

 oceans the earth's crust assumed a definite solid thickness before 

 the continents, and that in contracting, these thicker portions 

 exerci-ed a pressure upon the 'fluid nucleus tending to elevate 

 still further the continents. This hypothesis, M. Faye thinks, 

 will moreover explain the unequal distribntion of land and sea 

 around the two poles ; the general rise and fall 'of continents 

 being determined by the excess of density of the crust below the 

 oceans, and by the lines or points of least resistance to internal 

 pressure being at the middle of continents or at the margin of 

 the oceans. 



