March 23, 1893] 



NATURE 



497 



peratures. In one MM. Moissan and Violle describe two forms 

 of electric furnace which they have used in their experiments. 

 The substance to be heated is contained in a small crucible 

 made of carbon having two holes pierced through its side to 

 allow the carbon rods, between which the arc is formed, to 

 pass. This crucible is surrounded by blocks of lime to le- 

 duce the loss of heat on account of radiation. In one form 

 of furnace there is an arrangement by which a piece of graphite, 

 after being heated in the arc, is allowed to fall into a calori- 

 meter, and by this means they have found that a temperature of 

 3000° can be reached. In the other paper MM. Lagrange and 

 Hoho have investigated the fact, observed by Plantc and others, 

 that when you pass a sufficiently strong current through an 

 electrolyte, using as negative electrode a fine wire, and as posi- 

 tive electrode a conductor of considerable surface, a kind of 

 luminous sheath is formed round the negative electrode. The 

 authors find that the heat developed in this sheath is very great, 

 and that by its means a very intense heat can be applied at any 

 point of a body while, on account of the rapidity with which the 

 heat is disengaged, the rest of the body remains cold. As an 

 application of this method they have heated to a bright red the 

 outside of a bar of steel, while the inside remained compara- 

 tively cool, then by merely stopping the current the cold liquid 

 has come in contact with the hot steel. In this way they have 

 hardened the outside of bars of steel, while the inside has 

 remained soft and therefore tough. 



Prof. L. Weber, of Kiel, has recently constructed a 

 mercury barometer which can be filled without boiling, and 

 whose vacuum can be freed from residual air at any time in a 

 few seconds. It consists, according to the Zeitschrijt fiir 

 Instriimeiitenkunde, of a vertical lube with two bulbs, one on 

 each side. One of these bulbs ends in a tube to which an 

 indiarubber tube can be attached. The other is connected by 

 a shoit tube with a capillary constriction. A narrow tube con- 

 nects the lower end of the bulb with the top of the main tube, 

 thus forming a kind of double barometer. To fill it mercury is 

 poured into the first bulb and allowed to enter the main tube. 

 In doing so it forces the air down through the narrow tube and 

 out by the second bulb. Some mercury also enters the latter 

 by the capillary constriction. On placing the instrument in a 

 vertical position a vacuum is formed at the top of the two com- 

 municating tubes, which is slightly longer in the narrow one 

 owing to capillary depression. Barometric readings are then 

 taken in the usual way by means of a scale fixed to the main 

 tube. The vacuum can be tested and easily restored in the 

 following wa^ : The indiarubber tube attached to the first bulb 

 ends in an elastic ball with a small hole in it. This hole is 

 closed l)y the thumb and the ball is compressed. Mercury is 

 thus forced up the main tube and over into the capillary tube. 

 If there is any residual air it will form a bubble between the two 

 columns, which will on further compression be driven out 

 through the second bulb. On releasing the pressure the vacuum 

 is re-established, and the slight difference of level, in the two 

 bulbs is gradually obliterated by the passage of mercury through 

 the capillary contraction. The latter can be replaced by a glass 

 rod with a conically ground end, by means of which the com- 

 munication between the two bulbs can be temporarily inter- 

 rupted. 



An interesting communication concerning metallic osmium is 

 contributed to the current number of the Comptes Kendus by 

 MM. Joly and Vezes. Metallic osmium, as usually prepared by 

 the method of Berzelius, which consists in calcining the sulphide 

 in a carbon crucible, takes the form of a powder or a spongy 

 mass of a blue colour. As thus obtained it is rapidly attacked 

 by the oxygen of the air with production of the volatile and 

 dangerously poisonous tetroxide OSO4 ; hence the metal con- 

 stantly exhales a strong odour due to the vapour of the tetroxide. 

 NO. 122 I, VOL. 47] 



Sainte-Claire Deville and Debray some time ago succeeded in 

 obtaining metallic osmium in the form of beautiful little greyish 

 blue crystals, by passing the vapour of the tetroxide through a 

 strongly heated carbon tube. The density of these crystals, 

 22"48, was the highest which has been observed for the metal. 

 All the efforts, however, of .Sainte-Claire Deville and Debray 

 to fuse osmium in the flame of the oxyhydrogen blowpipe were 

 unavailing. If enclostd in a crucible of carbon surrounded by 

 another of lime, the metal simply remained unchanged, but if 

 heated directly in the flame itself it rapidly disappeared, owing 

 to its conversion into the volatile tetroxide, but no trace of fusion 

 was ever observed. It is now shown that osmium does melt at 

 the temperature of a very powerful electric arc, in a manner 

 analogous to ruthenium. It is, of course, essential that special 

 precautions should be taken in order to prevent loss of the 

 extremely expensive metal by oxidation, and consequently 

 volatility, particularly as the volatile product of the oxidation, 

 the tetroxide, is so injurious to the experimenter. The opera- 

 tion was therefore performed in the electric furnace devised by 

 Ducretet and Lejeune, which enabled the metal to be healed in 

 a carbon crucible placed in a closed chamber traversed by a 

 stream of carbon dioxide. Under these conditions when osmium 

 is rapidly raised to the highest temperature of the electric arc it 

 melts without sensible loss by volatilisation. After fusion 

 osmium presents a very brilliant metallic surface of a beautiful 

 blue colour slightly tinged with grey. It breaks with a crystal- 

 line fracture, and is distinguished by its remarkable hardness, 

 being harder than both ruthenium and iridium, readily cutting 

 glass and scratching quartz. Moreover, after fusion osmium 

 appears to be no longer attacked by the atmospheric oxygen, its 

 surface remaining bright greyish-blue. 



The whole of the refractory metals of the platinum family 

 have now been obtained in the liquid form. Of them all osmium 

 has been found the most refractory, its melting point being con- 

 siderably higher than that of ruthenium. It resembles the latter 

 metal very much in many of its properties, particularly as regards 

 the ready formation of a volatile tetroxide. It diff"ers entirely, 

 however, from ruthenium in aspect, exhibiting as above 

 described a remarkable blue metallic lustre, while ruthenium is 

 more white than platinum, resembling in fact burnished silver. 

 The six metals of the platinum group would appear to more 

 particularly resemble each other in pairs, ruthenium and osmium 

 having many physical and chemical attributes in common, 

 rhodium and iridium being similarly very nearly allied, and 

 palladium and platinum forming the third pair. In many 

 respects, however, osmium exhibits a peculiar and somewhat 

 isolated character, more akin to that of the metalloidal ele- 

 ments ; indeed, .so marked is this that Deville and Debray 

 termed it the metalloid of the platinum group, Berzelius com- 

 pared it to arsenic, and Dumas to tellurium. 



Notes from the Marine Biological Station, Plymouth : — 

 Little change has been observed in the floating fauna since last 

 week. Sarsia prolijera zxiAxatAyiiTR oi Clytia yohnstoiiiha.\t 

 again been taken ; and Obelia medusre have been plentiful, 

 although for the most part very small and immature. A few 

 Polydora larvae have been taken. Evadne Nordiiiaiiiti, which 

 at times is abundant in the surface waters, has made its first 

 appearance for the year ; the few individuals noticed were 

 carrying embryos in the brood pouch. The Nemertine Cephalo- 

 thrix lineare and the crabs Portuntis dcpiirator and holsalus 

 have begun to breed. 



The additions to the Zoological Society's Gardens during the 

 past week include eleven Orbicular Horned Lizards {Pliryitosoma 

 orbicidaie) from California, presented by Mr. William Chamber- 

 lain ; a Stanley Parrakeet {Platycenits icterotis) from Australia, 

 deposited ; a wandering Albatross {Diomedea cxtilans) captured 



