20 



NATURE 



[November i, i8 o 



The current number of Himmel khi/ ifn/^ contains a sum- 

 mary of a lecture by the Director of the Statistical Office of 

 Berlin, on the increase of damage by lightning, and on the effect 

 of lightning on the human body. The increase, which is unmis- 

 takable, is attributed to various causes, viz. the employn-.ent of 

 electricity in various industries, the continual change of the 

 form of the earth's surface by deforestation, drainajie, ^"iic, and 

 the impurities introduced into the atmosphere by the growing 

 consumption of coal. Prof, von Bezald has shown, some time 

 since, that for Bavaria the average yearly number of fires 

 caused by lightning amounted to 32 from 1S33-43. to 52 from 

 1S44-65, to 103 from 1866-79, »nd 'o '32 between 1 880 and 

 18S2. While in the year 1855, 134 persons were struck by 

 lightning, and 73 were killed, the numbers thirty years later 

 reached 1S9 and 161 respectively. It is noteworthy that persons 

 struck by lightning generally perceive neither lightning nor 

 thunder, but have the idea of being suddenly enveloped by fire. 



To the facts of fishes out of water and of cr.ibs on dry land 

 we are accustomed, but the recent announcement of the dis- 

 covery of a flying Copepod is a novelty of which the naturalist 

 has probably never dreamed, though Giesbrecht's beautiful 

 figures of the Naples form; might well have induced the thought 

 of such a possibility. In the current number of the Zoolo^ischer 

 Anzeigcr (No. 459), Dr. Ostroumoff, of the Sebastopol 

 Biological Station, state; that he and his son were coasting 

 along the Khersonese peninsula on a calm clear morning last 

 July, when they noticed numbers of the tiny green Crustacean, 

 PonlcUina mcditerranca (Claus), flying just above the level of 

 the water. " Many of these Copepods were resting on the sur- 

 face-film, took springs into the air, where they described a long 

 curve, and fell down again upon the water surface." Dr. 

 Ostroumoff traces the origin of this very exceptional habit to a 

 peculiarity in the manner of exuviation that Poiitellina 

 probably shares with certain other pelagic Entomostraca, e.g. 

 Evadne, PUopts, which cast their skins at the surface of the 

 water " by the help of the air which becomes entangled in 

 {atihtilt) their rejected coverings." We should like to hear some- 

 thing more upon this interesting phenomenon, which involves 

 a complete change in the life conditions of the species. It is 

 difficult, at any rate, to imagine that so light and hairy a form 

 as Pontillina can return at will to the water again after once 

 breaking through the surface film. 



The Bunsen flame spectra of the metals of the alkalies and 

 the alkaline earths have been studied by Herren J. M. Eder 

 and £. Valenta, by means of an apparatus which enabled 

 them to make exposures of extraordinary length. The 

 apparatus, described in a paper communicated to the Vienna 

 Academy, consisted essentially of a circular strip of platinum 

 gauze mounted in a slanting position on a nickel wheel. The 

 lower edge dipped into a solution of the salt to be examined, 

 and the upper edge passed through the Bunsen flame. The 

 wheel was kept slowly rotating by clockwork, and the steady 

 and uniform spectrum obtained was photographed. In the 

 case of sodium and potassium no lines were discovered that 

 were not already known from the spark and arc spectra, 

 although the ultra-violet sodium lines of wave-lengths 3303 

 and 3853 were well rendered. But with an exposure of some 

 thirty hours a large number of new bands appeared in the 

 violet and ultra-violet spectra of the metals of the alkaline 

 earths. They belonged chiefly to the oxides, and consisted 

 partly of double band.s arranged pretty regularly on a 

 continuous background. The spectrum of boracic acid, 

 obtained by burning a mixture of coal gas and 15(0,11,), in a 

 Linnemann burner, showed six new violet and ultra-violet 

 bands, which by their general character and their regular distribu- 

 tion correspond to those previously observed in the visible 

 spectrum. 



NO. 1305, VOL. 51] 



-V REMARKABLE instance of the anomalous behaviour of 

 bodies at very low temperatures is given by M. Raoul Pictet in 

 the Revue Scientifique. For the preparation of pure chloroform 

 by crystallisation at - 69° C. he used two copper refrigerators, 

 of capacities of 2i and 32 litres respectively. The former being 

 more convenient, it was used for the first series of experiments. 

 About 2 kgr. of commercial chloroform were put into a glass 

 test-tube, placed in the refrigerator, and surrounded by a tern - 

 perature of about - 120°, as indicated by a sulphuric ether 

 thermometer. The chloroform appeared turbid at —40" or 

 -50°, and was filtered and further cooled. At — 68°'5 the 

 cooling ceased, and very transparent crystals of chloroform 

 appeared on the walls of the test-tube. The chemically pure 

 chloroform thus obtained was used with great success in the 

 Berlin hospit.ils, and larger quantities had to be obtained. M. 

 Pictet noticed with great surprise that chloroform, refrigerated 

 in the larger vessel, was cooled to -81^ without a trace of 

 crystallisation. To test for experimental errors the small 

 refrigerator was exposed to the same cooling process, and the 

 chloroform crystals plunged into tVie larger one. But the 

 crystals dissolved at once, though the same thermometer, 

 successively plunged in the two refrigerators, fell from - 6S°'5 

 to -81°, where no crystallisation was going on. Finally, the 

 whole test-tube, with crystals at the walls, liquid chloroform 

 in the centre, and thermometer standing at -6S''S, was im- 

 mersed bodily in the liquid chloroform at -81°. The thermo- 

 meter gradually fell from -6S''5 to -St", while the crystals 

 dissolved before the observer's eyes. M. Pictet works out an 

 explanation of this striking phenomena on the basis of the theory 

 of radiation and his own theory of the molecular constitution 

 of solids and liquids, which leads him to the conclusion that 

 heat oscillations corresponding to low temperatures traverse 

 bad heat conductors with greater facility than they do compact 

 and heavy substances such as metals. 



The fifth report upon the activity of the German Imperial 

 Physico- Technical Institute appears in the Ziitichiifl fiir 

 Instrtimentenkiinde. Besides the electrical work, which chiefly 

 dealt with resistances, the principal subjects of investigation 

 were connected with thermometers, manometers, barometers, 

 pyrometers, standard Hefner lamps and photometry, and the 

 physical properties of various kinds of glass. The branch 

 establishment at Ilmenau, in the Grand Duchy of Saxony, 

 has been extended by the addition of a technical school 

 for workers in glass instruments. Among the barometers 

 tested were the aneroids employed by Dr. von Drygalski 

 on his Greenland expedition. It appeared that low temperatures 

 are capableof creating a temporary disturbance in the indications 

 of these instruments. The chief optical work was connected 

 with |)hotometry. .\s regards the introduction of the Hefner 

 lamp as a standard of illumination, the report points out that 

 Germany is ahead of other countries in possessing a well- 

 authenticated standard of light which answers all itechnical 

 requirements. Recently the Institute has endeavoured to con- 

 struct simple and portable photometers for technical purposes. 

 Two such instruments have been constructed and found to 

 work well. The photometry of the arc lamps illuminating 

 " Unter den Linden " at Berlin, was also taken in hand by the 

 Institute. The examination of different glasses related mainly 

 to their solubility in water, which was found to give an indica- 

 tion of various other properties. The electrolytic precipitation 

 of zinc and other metals from dilute solutions was investigated 

 with a view to their preparation in a pure state. The examina- 

 tion of specimens of steel, of chronometer oils, and of coloured 

 thermometer liquids, was among the many tasks allotted to this 

 most useful and many-sided National Physical Laboratory. 



Is the Pitt Press Mathematical Series there is no more useful 

 volume than "Arithmetic for Schools," by Mr. Charles Smith. 



