January 27, 1898] 



NATURE 



?oi 



with the Museum, were devoted at first to the hymenopterous 

 fauna of Middle Europe, on which his chief work was " Die 

 Hymenopteren Deutschlands " (1866). These writings were 

 largely compendiums of existing information, and his chief 

 claim to recollection rests on the production of several valuable 

 handbooks on the injurious insects of Germany, such as his 

 '* Entomologie fiir Gartner und Gartenfreunde " (1871) ; 

 " Forstwirthschaftliche Insektenkunde " (1874); " Praktische 

 Insektenkunde " (1879-80); and "Die Insekten nach ihrem 

 Schaden und Nutzen" (1882). His " Praktischen Insekten- 

 kunde," in particular, published in five parts, is an excellent 

 account of the characters, bionomics and economy of all the 

 more important injurious insects of Middle Europe, arranged 

 according to systematic position, and not, as is generally the 

 case, in relation to the nature of the damage they occasion. In 

 the absence of any satisfactory general text-book on the subject 

 published in this country, this work is indispensable to any 

 serious study of injurious insects in Great Britain, as well as in 

 Germany. Save for a single paper on Hymenoptera, which 

 appeared in 1891, Dr. Taschenberg published nothing on 

 entomology during the past fifteen years. 



For some time past the weather has been unusually mild for 

 the time of year, and the returns received by the Meteorological 

 Office show that higher temperatures have occurred in parts of 

 the British Islands during the past week than in any January 

 during the last twenty-five years at least. At Wick a tempera- 

 ture of 60" was recorded on the 19th, which is 3° higher than 

 any previous record in this month, and in other parts of Scot- 

 land almost equally high readings were observed. The Weekly 

 Weather Report of the 22nd inst. showed that the temperature 

 was 7" or 8° above the mean in all districts except the north of 

 Scotland, where it was 5° above the average. 



The current-intensity of a lightning flash is difficult to deter- 

 mine, smce we cannot well send it through a galvanometer and 

 determine the magnetic field produced by it. But there are 

 other lines along which we can approach the problem, as has 

 recently been indicated by F. Pockels in the jubilee number of 

 Wiedernann^s Annalen. It has been noticed that some rocks 

 found on the surface of the earth exhibit a magnetisation which 

 is quite out of keeping with the earth's ordinary magnetism. 

 The probability is at once suggested that their magnetisation 

 may be due to lightning discharges in the neighbourhood. Herr 

 Pockels cut some rods out of the basalt of the Winterberg in 

 Saxony which showed such irregular magnetism, and found on 

 testing them that the permanent magnetism they possessed 

 could only be imparted to them by a current of at least 2900 

 amperes passing along the surface of the rock. If the discharge 

 did not pass there, it must have been a good deal stronger, so 

 that this is only a minimum value. Later on, he cut some basalt 

 in the neighbourhood of a tree which had been damaged by 

 lightning, a circumstance which gave him some clue to the dis- 

 tance at which the current passed. The value then obtained 

 for the current strength of the lightning was 6500 amperes. 



M. Armand Vire contributes to the Revue g^n^rale des 

 Sciences for December 30, a highly interesting paper on subter- 

 ranean fauna, which he has made the subject of extended study, 

 both in the catacombs of Paris and in the large caves of the 

 Jura, the Pyrenees, and the central plateau of France. A 

 number of illustrations are given of the caecal forms of arthro- 

 pods and Crustacea discovered by M. Vire, several of which 

 have been described as new species, though the author has 

 endeavoured to refer them to existing forms which have be- 

 come modified by environment. Most of these cave inhabitants 

 are characterised by the extraordinary development of their 

 tactile and auditory organs, their antennae, legs, and even their 

 bodies being covered with fine hairs highly sensitive to the 



NO. 1474. VOL. 57] 



slightest disturbance. In searching for transitional types, M. 

 Vire has met with a fair measure of success. In the case of 

 Aselius aquaticus, both normal and subterranean forms exist, 

 the latter presenting marked differences in their antennules. 

 The author considers that the subterranean genus of beetles, 

 Anophthalmus, is probably referable to Trechus, and that the 

 new species, Niphargus viret, is possibly a modified form of 

 Gammarus. Finally, M. Vire suggests the desirability of an 

 extended series of experiments on these transitional forms, with 

 a view of ascertaining how far they tend to revert to the normal 

 types on being restored to light. 



The transformation of Rontgen rays by metals forms the sub- 

 ject of a note contributed to the Societe Fran9aise de Physique, 

 by M. G. Sagnac {^Bulletin, No. 106). When such rays are in- 

 cident on a metal surface they are not perceptibly reflected, but 

 the superficial layer transforms them into secondary rays capable 

 of producing photographic impressions, of exciting fluorescent 

 screens, or of discharging electrification. These secondary rays 

 differ from ordinary Rontgen rays in that they are freely ab- 

 sorbed by aluminium, the absorption giving rise to a further 

 kind of tertiary rays, still more readily absorbed by aluminium. 

 M. Sagnac suggests that the secondary and tertiary rays may be 

 intermediate between true Rontgen and Lenard rays. 



An important memoir on the magnetic properties of tempered 

 steel has been communicated to the Societe d' Encouragement 

 pour rindustrie Nationale, for publication in their Bulletin. 

 The authoress, Madame Sklodowska Curie, discusses which are 

 the best kinds of steel for the construction of permanent 

 magnets. In the first series of experiments, bars and occasion- 

 ally rings of steel were heated in an electric furnace the spiral 

 current of which at the same time furnished the magnetic field. 

 It was found that steel does not take the temper unless heated 

 to a temperature superior to that at which its magnetic properties 

 change. Among various steels, those containing i '2 per cent, of 

 carbon were found best suited for the construction of permanent 

 magnets. Madame Sklodowska Curie has also considered the 

 presence of different metals in steel. While these do not usually 

 modify the residual magnetisation, they often considerably 

 ncrease the coercitive field, i.e. the field required to cause de- 

 magnetisation ; the addition of tungsten or molybdenum furnish- 

 ing the best steel for magnets. The paper concludes with an 

 examination of the stability of magnetisation in bars, the effect 

 of blows and of variations of temperature being specially con- 

 sidered. The greater the coercitive field the less is the effect of 

 blows ; heating to 200° considerably affects good magnetic 

 steel, even a temperature of 100° is detrimental, while the best 

 permanent magnets are made by heating the steel to only 60" 

 and partially demagnetising it after having magnetised it to 

 the point of saturation. 



The Journal de Physique for January contains, in addition 

 to abstracts, papers by M. A. Leduc, on the densities, molecular 

 volumes, compres.sibility, and dilatation of gases at different 

 temperatures and at mean pressures ; by M. H. Pellat, on the 

 variation of energy in isothermal transformations considered with 

 special reference to electric energy ; by MM. Pellat and 

 Sacerdote, on contact phenomena; and by M. G. Sagnac, on 

 diffraction of plane waves by slits and gratings. 



An atlas of the currents of the Pacific Ocean has just been 

 published by the Hydrographer of the Admiralty from inform- 

 ation collated and prepared in the Meteorological Office. This 

 is the third volume of current charts for the great oceans that 

 has recently been issued in the same way, with the view of 

 providing the navigator with the best available information. 

 The sources from which the observations were obtained 

 being (i) logs received in the Meteorological Office, mainly 

 from the Mercantile Marine, from 1854-96 ; (2) logs and 



