424 



NA TURE 



[March 2, 189^ 



Sciences. Mr. Dean states that there is a marked difference in 

 the irritability of different leaves ; that the leaves usually fail in 

 capturing the larger and more active insects ; that even small 

 insects constantly escape ; and that the leaf repeatedly closes on 

 inorganic and vegetable objects. 



Mr. W. Saville-Kent's book on "The Great Barrier 

 Reef of Australia " will be ready for publication before the end 

 of the present month. It will include a series of photographic 

 views of coral reefs of various construction from several selected 

 localities, with similar and also coloured illustrations and 

 descriptions of the living corolla, coral-polyps, and other 

 marine organisms commonly associated on the reefs. Mean- 

 while, Messrs. W. H. Allen and Co., who are to publish the 

 book, have issued enlarged and very beautiful copies of some 

 of the principal illustrations. These are intended for the use 

 of museums, colleges, and natural history societies, and will 

 certainly be highly appreciated wherever they may happen to 

 be introduced. 



A TRANSLATION of Prof. Weismann's "Das Keimplasma,'' 

 recently reviewed in Nature, has been issued in " The Con- 

 temporary Science Series" (WaUer Scott). The translators 

 are Prof. W. N. Parker and Harriet Ronnfeldt, who have done 

 their work carefully. In the preface Prof. Parker explains 

 that in the case of special technical terms which have no recog- 

 nised English equivalents he has added the German words in 

 brackets the first time they are used. He has had the great 

 advantage of being able to consult Prof. Weismann personally 

 with regard to many of the more difficult passages. . 



The County Council of Northumberland has issued a valuable 

 pamphlet, by Dr. W. Somerville, giving an account of experi- 

 ments made last season throughout Northumberland with a view 

 of gaining practical information regarding some points connected 

 with the economic manuring of the turnip crop. 



Messrs. Methuen and Co. have added to their " Univer- 

 sity Extension Series" a volume on "The Mechanics of 

 Daily Life," by V, P. Sells. The author makes no attempt at 

 the mathematical treatment generally adopted, but seeks rather 

 to use the subject " as a means of scientific training, and as an 

 illustration of the method of examining nature by reasoning 

 and experiment." 



Messrs. Cassell and Co. are publishing in monthly parts 

 a new issue of Dr, Robert Brown's " Our Earth and its 

 Story," with many coloured plates, maps, and upwards of 700 

 illustrations. 



Two important papers upon the ready preparation of large 

 quantities of the more refractory metals by means of the electric 

 furnace are contributed by M. Moissan to the current number of 

 ihQ Comptes Rendus. The " electric furnace " is simply a small 

 furnace constructed of lime, so arranged that it can be intensely 

 heated by a very powerful electric arc. A quantity of magnesia, 

 which M. Moissan finds to be perfectly stable even at this high 

 temperature, is first placed in the cavity of the furnace, and 

 upon this the crucible of retort-carbon containing a mixture of 

 powdered carbon and the metallic oxide to be reduced. When 

 the metaMs volatile a current of hydrogen is passed through the 

 furnace, and the vaporised metal is condensed in a compara- 

 tively cool receiver. In this manner M. Moissan has succeeded 

 in rapidly preparing considerable quantities of the metals of the 

 alkaline earths, calcium, strontium, and barium. If the metal 

 is not sensibly volatile it is left in the crucible after the reduc- 

 tion in the form of an ingot. The rare metal uranium, and the 

 metals manganese and chromium belong to this category, and 

 their preparation forms the subject of M. Moissan's two com- 

 munications. 



NO. 12X8, VOL. 47] 



Metallic uranium was prepared with great difficulty, and 

 only in small quantities by Peligot, by reducing the oxide with 

 an alkali metal. At ordinarily procurable temperatures the 

 various oxides of uranium are practically irreducible by carbon. 

 This no longer obtains, however, at the extremely high tempera- 

 ture of a very powerful electric arc. The nitrate of uranium is 

 first calcined in a porcelain crucible, whereby a reddish-coloured 

 mixture of the sesquioxide and of the green oxide U3O4 is 

 obtained. This mixed oxide is then well ground with a very 

 slight excess of powdered carbon, and the whole tightly packed 

 in the crucible of retort-carbon, which is afterwards placed in 

 position in the lime furnace. Upon submitting the mixture in the 

 crucible to the action of the arc produced by a current of 450 

 amperes, the reduction is completely effected in a few minutes. 

 The ingot of uranium thus produced exhibits a brilliant fracture 

 and great hardness. It possesses the peculiar property of send- 

 ing forth a shower of incandescent sparks when struck against 

 a piece of porcelain, or when fragments of it are shaken about in 

 a glass flask, reminding one of the combustion of particles of 

 freshly-reduced iron when allowed to fall through the air. The 

 yield of the metal is very considerable ; thus in one experiment 

 of twelve minutes' duration an ingot weighing over two hundred 

 grams was produced. The metal is not quite free from carbon, 

 the amount of the latter depending upon the excess used. M. 

 Moissan is now engaged in perfecting a ready mode of refining it. 

 In order to prepare metallic manganese the protoxide is mixed 

 with carbon as in the case of uranium, and the mixture sub- 

 mitted to the arc produced by a current of 300 amperes. The 

 reduction is completely effected in five or six minutes, an ingot 

 of 120 grams being readily obtained. The comparatively weaker 

 arc derived from a current of only 100 amperes gives the same 

 yield in 10-15 minutes. Any large excess of carbon is to be 

 avoided as carbides of manganese are then produced. If an 

 excess of the oxide is employed the metallic manganese obtained 

 is almost pure, and may be preserved unchanged in open vessels. 

 I The carbides, however, are rapidly attacked by the moisture of 

 the atmosphere, and if thrown into water evolve a gaseous mix- 

 ture of hydrogen and various hydrocarbons. Chromium has 

 always been found hitherto to be much more difficult to reduce 

 than manganese, but complete reduction occurs in 8-10 minutes 

 in the electric furnace, employing a mixture of the sesquioxide 

 and carbon and a current of 350 amperes, the yield being an 

 ingot of 100 grams. A current of only 30 amperes, however, is 

 sufficient to produce ten grams of the metal in half an hour's 

 time. Moreover, it is possible to refine the somewhat impure 

 (from carbide) metal by a simple repetition of the process in 

 presence of a fresh quantity of the sesquioxide. The pure 

 chromium thus obtained is completely transformed into the vola- 

 tile chloride when heated in a stream of chlorine. The reduction 

 in the electric arc succeeds equally well with crude chrome iron 

 ore, an alloy of iron and chromium being obtained from which 

 the chromium may very readily be converted into chromate by 

 projecting it into fused nitrate of potash or soda and subsequent 

 extraction with water. 



Notes from the Marine Biological Station, Plymouth.— 

 During the past week ephyrae of Aurelia have become quite 

 plentiful in the Sound. The Anthomedusas have been repre- 

 sented by numbers of the charming Rathkea octopunctata of 

 Haeckel ; and the Leptomedusae (which are still scarce) by 

 isolated examples of several species, including the Thaumaniias 

 octona of Forbes. Ctenophore ova and several larval and 

 young Ctenophores have been noticed. The proportion of 

 Polychsete larvae and of Cirrhipede Nauplii remains fairly con- 

 stant \ while there has been an appreciable increase in the 

 numbers of Brachyurous Zooeae. The Hydroid Sertularia 

 ar^if«/^a and Actinian Cerais pedtmculaUis { — Sagarita hellis\ 

 are now breeding. 



