September 21, 1893] 



NATURE 



5" 



printed works, manuscripts, &c., once the property of the dis 

 Coverer of Vaccination. The catalogue is prefaced by a brief 

 memoir of Dr. Jenner. 



The September number of the Board of Trade Journal con- 

 tains an interesting account of the development of the World's 

 i Telephones, by M. Daniel Belief, translated from the Economiste 

 \ Francais, "A Summary of Agricultural Returns of Great 

 j Britain for 1893," " Coal Production in Japan," and many other 

 ' ite ms of interest. 



We have just received the Proceedings and Transactions of 

 j the Royal Society of Canada for the year 1892. The London 

 I agent for it is Mr. Bernard Quaritch. 



A LIST of observations made in 1892 by the members of the 



i 'aradoc Field Club, Shropshire, and others, has been issued 



under the title, " The Caradoc Record of Bare Facts." 



The report for 1892 of the Botanical Exchange Club of the 



j British Isles has just reached us. It is issued by Messrs. James 



1 Collins and Co., Manchester. 



The Calendar of the Durham College of Science, Newcastle- 

 on-Tyne, for the session 1893-94 has reached us. It is pub- 

 { lished by Messrs. Andrew Reid, Sons, and Co., London, and 

 Newcastle-on-Tyne. 



Messrs. F. and E. Gibbons, Liverpool, have issued pro- 

 |S pectuses of Day Classes in Arts and Science, and of the Evening 

 I Lectures, and of the Department of Engineering, in connection 

 with the University College, Liverpool, for the session 1893-94. 

 I They contain all the preliminary information which intending 

 students are likely to require. 



j The Calendar for 1893-94 of the Gla.^gow and West of 

 jScotland Technical College has just been published by Mr. Robert 

 Anderson, Glasgow. 



I Dr. W. H. Pearse has sent' us a copy of the address de- 

 livered by him as president of the Plymouth Institution 

 and Devon and Cornwall Natural History Society, at the 

 -opening meeting of the session 1892-93. It deals with the 

 .subject of our present knowledge of biological science. 



Wk have received a printed circular signed "A Free Lance," 

 condemning a recent action of ours in refusing to print a letter 

 from the author on the subject of the "Publication of Physical 

 'Papers" unless, in accordance with the rule to which attention 

 is drawn in every number of Nature, he divulged his name. 

 We fail to see any adequate reason for violating our rule in the 

 favour of " A Free Lance" more than in the case of any other 

 3f our correspondents. 



The products of the sublimation of arsenic form the subject 

 >f an important communication to the latest number of the 

 /citschrijt filr Anorganische Chemie, by Dr. Retgers. The 

 ,i(arious allotropic modifications of the element have been sub- 

 jjected to a searching investigation, and further interesting 

 nformation has been acquired concerning the little known solid 

 pydride of arsenic AsH, and the suboxide AsjO, whose 

 Bxistence has hitherto been considered doubtful. It is first 

 •ihown that there is no amorphous modification of arsenic, the 

 jleposit of so called "black amorphous arsenic," obtained dur- 

 ng the sublimation of the element in a current of hydrogen and 

 n a number of high temperature decompositions of arsenic com- 

 )Ounds, is found to be microcrystalline and to exhibit distinct 

 ;vidence that it consists of the ordinary regular variety. There 

 .re consequently only two well-defined allotropic modifications 

 |>f arsenic : (i) the stable form which crystallises in the hexagonal 

 'ystera, is silver-white in appearance, specifically heavy, and 

 jequires a comparatively high temperature for volatilisation ; 

 ;ind (2) the specifically lighter and more volatile modification 

 |(vhich crystallises in regular octahedrons, and exhibits a black 

 'urface. When arsenic is heated to the point of sublimation in 

 NO. 1247, VOL. 48] 



a current of indifierent gas, the first variety condenses nearest 

 the heated element, while the second variety, owing to its lowe 

 temperature of volatilisation, is deposited more remote from the 

 portion of the tube which is heated by the flame. These two 

 forms of arsenic correspond completelv with the two modifica- 

 tions of phosphorus, the regular black variety with the regular 

 yellow modification of phosphorus, and the silver-white 

 hexagonal form with the hexagonal red ph..s(ihorus. Dr. Retgers 

 adduces some evidence also in support of the view that there is 

 a third crystalline modification of arsenic, of which the 

 crystals belong to the raonoclinic system. The fact is 

 also recorded that elementary arsenic, of whatever modi- 

 fication, is invariably opaque even when in the finest state of 

 division ; former observations of yellow and brown transparent 

 arsenic are shown to have been due to compounds having been 

 mistaken for the element. The brown spots which are deposited 

 along with arsenic when the flame from a Marsh's apparatus is 

 allowed to impinge upon cold porcelain, or which form in the 

 Marsh sublimation tube, do not consist of the element in thin 

 layers, but of the brown solid hydride AsH, which is produced 

 by the partial dissociation of the gaseous trihydride AsHj. 

 When the last-named substance is heated during its passage along 

 the sublimation tube, the arsenic mirror consists of both modi- 

 fications of the element, the silver-white hexagonal form nearest 

 the flame, and the black regular variety further removed. The 

 brown deposit of solid hydride AsH is always found furthest 

 removed of all, and thus forms, as it were, the tail of the mirror 

 Dr. Retgers finds that boiling xylene readily dissolves this solid 

 hydride, thus affording an excellent mode of distinguishing it 

 from elementary arsenic, which is totally insoluble in xylene. 



The solid hydride of arsenic was isolated some years ago by 

 Janowsky, who obtained it as a brown velvet-like substance by 

 decomposing potassium or sodium arsenide with water. Ogier 

 has subsequently shown that it may likewise be obtained by the 

 action of the silent electrical discharge upon the gaseous trihy- 

 dride. The existence of the suboxide of arsenic has hitherto 

 been so doubtful that the compilers of the new edition of 

 " Watt's Dictionary of Chemistry " feel justified in stating that 

 " no definite proof of the existence of an oxide with less oxygen 

 than As^G,; has been given." Dr. Retgers, however, adduces 

 weighty evidence in favour of the supposition. As explained 

 above, when arsenic is sublimed in a current of inert gas (carbon 

 dioxide, for instance), a deposit consisting of the two modifica- 

 tions of the element, white and black, is obtained. The moment, 

 however, that a little oxygen or air is allowed to mix with the 

 carbon dioxide a broivn annulus commences to form between 

 the white and the black elementary deposits. This brown sub- 

 limate is not crystalline, and is transparent, the thin films proving 

 to be quite isotropic in polarised light. In order to produce a 

 broad deposit of this brown substance it is advisable to employ 

 a wide tube, and to stop the experiment as soon as the annulus 

 is formed, as further heating soon decomposes it again. From 

 this and further evidence adduced by Dr. Retgers, there can be 

 no longer any reasonable doubt that a lower oxide of arsenic, 

 probably As„0, is capable of existence. 



The additions to the Zoological Society's Gardens during 

 the past week include a Campbell's Monkey (Cercofithecus 

 campbelli, 9 ) from West Africa, presented by Miss Jane 

 Richards ; a Pig-tailed Monkey {Macactts nemestrintis, i ) from 

 Java, presented by Miss Llewellyn ; an Azara's Capuchin 

 {Cebus azam,^) from Paraguay, presented by Miss Hairby ; 

 two Common Marmosets {lla-paU jacchus) from South-East 

 Brazil, presented by Mr. E. Lake ; two Lions [Felis leo, i 9 ) 

 from East Africa, presented by H.H. the Sultan of Zanzibar : 

 two Egyptian Jerboas (Dipus agypliiis) from Egypt, presented 

 by Miss B. Dell ; two Egyptian Jerboas {Dipits legyptius) from 



