Feb. 28, 1884] 



-NATURE 



417 



been lost. Notwithstanding the absence of this conclusive proof, 

 northern scholars are inclined to accept the later transcript as a 

 bona fale \eti\on of the original before the loss of its missing 

 parts, and if this assumption can be maintained, we have evi- 

 dence that the Northmen advanced four days' journey north of 

 76°. The object of the expedition, we are informed, was to 

 discover what lands and people were to be found north of the 

 Christian Station at Garde, and whether the much dreaded 

 Skrollinger or native Esquimaux occupied those unknown 

 regions in any formidable numbers. The seamen, we are told, saw 

 many islands on which there were traces of the presence of these 

 people, but they were unable to land, owing to the number of 

 bears which, together with numerous seals and whales, frequented 

 the coasts. In reference to the high latitude said to have been 

 reached by these early explorers, and which is inferred from the 

 description of the height of the sun on St. James's Day (July 25), 

 it may be observed that a runic stone was found in 1S24 in 

 72° 55' N. lat., about twenty miles northwest of Upernivik, 

 the northernmost existing Danish station. The inscription, 

 which records that three men, whose names are given, erected 

 the stone as a landmark, concludes with six runic characters, 

 which have been variously interpreted to indicate the years 1135 

 and 1235. 



Krom his scientific expedition to Anatolia, Syria, Egypt, 

 India, Indo-China, China, and Japan during the years 18S0-83, 

 Dr. Emil Riebeck has lately returned to Europe laden with 

 ethnological and archceological treasures of all sorts. This 

 splendid collection, on which the enterprising explorer has ex- 

 pended no less than 30,003/., has during the past few mouths 

 formed a chief attraction to naturalists in Berlin, where it has 

 been on exhibition at the Kunstgewerbe Mu-eum. Here the 

 available space was not sufficient to allow of a thoroughly syste- 

 matic arrangement of the objects, which however have been 

 roughly disposed in three main geographical groups : — ( i ) Western 

 Asia and Africa ; (2) India and Further India ; (3) East A-ia 

 (China and Japan). Some idea of the immense variety of articles 

 here brought together may be had from the detailed catalogue of 

 Dr. Riebeck's "Asiatic Collection," recently issued by Messrs. 

 Weidmann of Berlin. From Palestine and Syria v\e have objects 

 of every description ; while the articles from Somaliland, which 

 are very numerous, illustrate almost every phase of the social life 

 of the little known inhabitants of that region. Several speci- 

 mens are shown of the masks used in Ceylon at the "devil 

 dances " performed during illness. The masks represent divini- 

 ties of the Hindu mythology, rakshasas or demons, nagakanyas 

 or snake masks, lions, tigers, crocodiles, negroes, Mussulmans, 

 Malays, &c. India is largely represented. Prom Burmah, where 

 the Irrawadi was ascended as far as Bhamo, were brought many 

 costly articles, such as royal coronets and dresses, alabaster and 

 gilt wooden statuettes of Buddha, masks of strolling minstrels 

 and players, amber rosaries, richly carved consols, lacquer ware, 

 ornamental drinking vessels, writing materials, ic. A vi:>it to 

 Bangkok yielded models of Siamese floating houses, fishing gear, 

 agricultural and industrial implements, &c. Amongst the most 

 characteristic objects from China are brightly painted clay 

 models of popular types, bronze v.ases, chased, inlaid in silver, 

 and studded with gems; shallow dishes of "imperial bronze" 

 (yellow picked out in red), silver teapots, artistic articles in jade, 

 rock crystal, and marble, &c. The rich and varied Japanese col- 

 lection comprises specimens of all the most characteristic produc- 

 tions of the country, especially Satsuma porcelain and other 

 ceramic ware, illustrating the development of Japanese porcelain 

 from the sixteenth to the nineteenth century. During the first 

 part of his journey Dr. Riebeck was accompanied by Dr. Moock, 

 who, after escaping from many perils amongst the Bedouin tribes 

 in the Moabite country, was diowned in crossing the Jordan, 

 and now lies buried in Jericho. During the visit to Egypt he 

 was attended as far as the Nubian frontier by Dr. Schwemfurth, 

 who again accompanied him in March l88l to the south coast of 

 Arabia and the I^land of Socotra. During the rest of his wan- 

 derings throughout the Far East Dr. Riebeck had for his asso- 

 ciates M. C. B. Rosset, who joined him in Germany, and Dr. 

 Mantei, whom he engaged in Egypt after the untimely death of 

 Dr. Moock. 



In the March part of Good Words Mr. Edward Whymper 

 gives some iiarticulars of his journeys in Greenland which have 

 not been heretofore published ; and states that he found the 

 height of the interior in the latitude of U menak (about 70° 30' N. ) 

 considerably exceeded 10,000 feet. Mr. Whymper says that 



from the various mountains he has ascended on the eastern side 

 of Davis Straits he has had continuous views of the glacier- 

 covered interior of Greenland between about 68° 30' and 7'° '5 

 N. lat., and that there is no break or depression within those 

 limits, and that the country is everywhere so absolutely covered 

 by snow and glacier that not a single rock or crag can be seen. 



ON THE PHENOMENA EXHIBITED BY 

 DUSTY AIR IN THE NEIGHBOURHOOD OF 

 STRONGLY ILLUMINATED BODIES^ 



TN 1870 Dr. Tyndall described the dark or dust-free plane 

 ■'• which rises from a hot body in illuminated dusty air, and 

 gave two explanations of the dust-freeness of this dark space. 

 Another explanation was suggested by Dr. Frankland. In 

 18S1 Lord Kayleigh re-examined the phenomenon, and dis- 

 covered that a cold body gave a similar down-streaming plane. 

 He also suggested a totally different explanation. The writers 

 discuss all these suggested explanations, and see reasons for 

 rejecting them all. They have, moreover, observed that the 

 dark plane rising from a hot body is only a prolongation of a 

 well-defined dust-free cocit of nearly uniform thickness under 

 ordinary circumstances surrounding the body, and they point out 

 that this dark coat is the thing really requiring explanation, the 

 dark plane being merely due to the up-carrying of portions of 

 this coat by convection currents. 



The preliminary experiments were described in a letter to 

 Nature last July (vol. xxviii. p. 297). 



The dark coat is found to increase in thickness with the tempera- 

 ture of the body, becoming very thick at high temperatures, say 

 1000° C, but being narrow for temperatures only a few degrees 

 above the air. When the temperature of the body is the same as 

 that of the air surrounding it, the dust-free coat is either non- 

 existent or exceedingly thin. The thickening of the coat by a rise 

 of temperature is interfered with by convection-currents, which 

 bv/eep the outer portions off more rapidly than they can be renewed, 

 and so make the coat thinner than it otherwise would be. By 

 means of a blast of air the coat can be almost wholly or entirely 

 blown away ; but convection-currents are never able to sweep it 

 off, for the same cause which increases the convection-currents 

 also broadens and assists the formation of the coat. The coat 

 can be seen on round rods of all materials, on flat plates, both 

 horizontal and vertical, on hollow and irregularly shaped pieces, 

 and in general on every substance whatever. Nevertheless the 

 behaviour of certain bodies is peculiar, and is detailed in the 

 paper ; such bodies, for instance, as a stick of phosphorus, which 

 itself gives off smoke, a volatile solid like camphor, moistened 

 solids like soaked carbjn, liquids like sulphuric acid water and 

 ether, and thin films of glass or mica. Other substances examined 

 are : copper, iron, zinc, electric-light carbon, charcoal, glass, 

 mica, selenite, selenium, Iceland spar, tourmaline, potash, rock- 

 salt, bismuth, silver, chalk, and all kinds of paper. In every 

 case the method of examination was as follows : — A glass box 

 was mounted in front of the nozzle of an electric lantern, and 

 the body to be examined was supported in any convenient 

 manner, so as to be about the middle of the box, and to be 

 well illuminated. Smoke was introduced, the lamp turned on, 

 and the effect examined by looking along the length of the body 

 at right angles to the light. Sometimes a microscope was used, 

 but it was not necessary except for measurements. A hand lens 

 is useful. For smoke, tobacco was the most common, but am- 

 monic chloride was used when a distinctly volatile smoke was 

 desired, and magnesic oxide whenever a non-volatile and incom- 

 bustible smoke was wanted. Any kind of smoke serves equally 

 well. Hydrogen and carbonic acid and other gases have been 

 used as well as air : in hydrogen the coat is much thicker, in 

 carbonic acid a little thinner, than in air. The effect of pressure 

 on the dark coat was examined, and it is found that the coat 

 broadens as the pressme diminishes. An increase in pressure 

 of 4^ atmospheres renders the coat very thin and sharp, and at 

 the same time causes the convection-currents to be sluggish. 



The writers considered that it would be very instructive to 

 examine whether a dark coat and plane could be observed when a 

 warm body was immersed in a dusty liquid ; and they accordingly 

 devoted a good deal of attention to this point. After failures with 

 mastic and other substances, they succeeded in observing a very 

 thin, dark coat on the surface of an iron wire immersed in water 



' Abstract of a paper by Oliver J. Lodge ani J. W. Clark, read at the 

 Physical Society, February 9. 



