2XO 



NATURE 



[January 4, 1894 



magnetic east and west. The deflection of the mirror was 

 measured by means of a microscope with a micrometer eyepiece, 

 such that one division of the scale corresponded to a deflection 

 of the mirror of o"'295 of arc, or to an elongation of 0805 ;< 

 10" cm. Experiments were made on wires of iron and nickel 

 of different lengths, and he finds in every case that the elongation 

 in iron and the contraction in nickel by magnetisation is accom- 

 panied by marked hysteresis. The curve of hysteresis is 

 syir-metrical with respect to the line of zero magnetising force, 

 so that the elongation or contraction during cyclic changes is an 

 even function of the magnetising force. When a wire has been 

 magnetised it cannot be brought to its original length by simply 

 reversing the magnetic field. 



In a note communicated to the same number of the Philo- 

 sophical Magazine, Prof. Knott calls attention to the similarity 

 between the effects observed by Mr. Nagaoka, and those which 

 he has himself observed in the case of magnetic-twist cycles for 

 iron and nickel. A steady current was passed along the wire 

 under observation, and the longitudinal field acting on the wire 

 was gradually altered between the limits itl, and at suitable 

 intervals observations of the twist made. It was found that 

 with a small range of field the hysteresis curve obtained by plot- 

 ting twist against field was very similar to the 1 well-known 

 hysteresis curve of magnetisation. With limiting fields, how- 

 ever, stronger than the field which produces the maximum 

 twist, the hysteresis curve crossed itself twice and formed three 

 loops. In the magneto-elongation cycle the change of sign 

 of the magnetising force does not produce a change of sign in 

 the elongation. On the other hand, in the magnetic-twist cycle, 

 as the magnetic force passes through zero from positive to nega- 

 tive, the twist tends to do the same, though with a lag. The 

 author considers that the twist, under a given combination of 

 circular and longitudinal magnetising forces, depends not only 

 upon the elongations but also upon some function of these forces 

 which changes sign wuh each, and to which the existence of the 

 maximum twist is largely if not entirely due. 



An entertaining chapter on minerals, and the popular super- 

 stitions connected with them in Germany, is contributed to Die 

 I^atur by Friedrich Klinkhardt. The fact that variety among 

 minerals is less easily perceived than that among plants and 

 animals, is emphasised by the great influence that "a stone" 

 pure and simple, without further specification, is capable of 

 exerting in the popular estimation. Children un Jer the age of one 

 may not play with stones, otherwise bread will be scarce. An 

 ill omen may be made innocuous by throwing a stone into the 

 road before taking the next breath. Chalk is credited with 

 many virtues, and is used both for its own efficacy and for 

 making signs with. Cows marked all down the spine with 

 chalk consecrated at Epiphany, remain healthy, and always 

 find their way home. Alabaster in water is used for curing sick 

 children in Bohemia. A flmt pebble from the brook, if thrown 

 over the roof into the poultry yard, encourages the hens to lay 

 eggs. The beliefs connected with " thunderbolts," which are 

 sometimes flint instruments, or quartz crystals, or lightning 

 tubes, are exceedingly numerous. In the Palatinate it is 

 believed that thunderbolts, after penetrating seven yards into 

 the ground, rise a yard every year ; this reminds one of Miolnir, 

 Thor's hammer, which returned to his hand. 



We read an interesting paper "On the Kulm District of 

 Lenzkirch in the Black Forest," by Dr. Rafael Herimann. A 

 geological map of the district is given, scale i : 5o>oo3 {Berichte 

 der Naturforschenden Gesellschajl zii Freiburg i. B., June, 1893). 

 In the Black Forest, just as in the Hartz and in Thiiringia, two 

 main series of carboniferous rocks are recognisable, an older 

 group of dark shales, and a younger formation of conglomeratic 

 rock. During the intermediate epoch, the upraising and folding 

 NO. 1262, VOL. 49] 



of the rocks took place, associated with intrusions of crystalline 

 rock. The eruptive rocks of the district are granite, coarse and 

 fine grained, granitite, granitic dykes, quartz porpyhry, porphy- 

 ritic dykes, and porphyritic breccias. Herrmann does not agree 

 witk Vogelgesang that the granite and granitite are petrogra- 

 phical varieties of one and the same rock united by a complete 

 transitional series, but regards them as two independent masses 

 of rock, differing in composition and structure. All the granitic 

 rocks have been intensely affected by pressure, whereas the 

 younger porphyry shows no appearance of it. Herrmann de- 

 duces, therefore, that the intrusion of porphyry marks what was 

 probably the last phase of folding and overthrusting of rocks Id 

 the Black Forest during the Carboniferous period. 



The region watered by the upper part of the Yenisei (which 

 is known to the Mongols under the name of Ulu-Khem, and 

 is made up by the confluence of the Bei-khem and the 

 Kha-khem) belonged until lately to the least known parts of 

 north-west Mongolia. The opinion expressed in the " General 

 Sketch of the Orography ot East Siberia " {Zapiski of the 

 Russian Geographical Society, vol. v. 1874), to the effect that 

 it must be a high plateau, and that the so-called circular chain 

 Erghik-targak-taiga is ^nothing but a border ridge, or often but 

 the steep slope of the ph-xteau, had been contested. Now it 

 finds its full confirmation in the recent exploration of the 

 region by Mr. Kryloff, published, with a map, in the Izveslia 

 of the Russian Geographical Society (vol. xxix. 4, 1893). 

 The whole region really has the above-menioned character. 

 After having left the valley of the main river, which has, even 

 at the junction of the two Khems, an altitude of 1873 feet, 

 Mr. Kryloff had to travel all the time on the level of the high 

 plateau, never finding altitudes less than 3000 feet, till he 

 returned to the Russian dominions in the basin of the Tuba. 

 Mr. Kryloff's journey having been performed for the St. 

 Petersburg Botanical Garden, special attention has been paid 

 by the explorer to the flora of the region; and he found that 

 the vegetation on the plateau assumes in many places the 

 character of a Steppe vegetation, namely, in the flat but high 

 valleys of the rivers, which are dotted by numerous small lakes. 

 At the sources of the Bei-khem, the flat surface of the water 

 parting, as well as large portions of the plateau itself, raise 

 above the level of the tree-vegetation, usually marked by the 

 cedar, and are covered with Alpine meadows. As to the 

 ridges which rise above the surface of the plateau, they attain 

 heights of over 7000 feet, and over 8000 feet in the Tannu-ola 

 ridge in the north of Lake Ubsa-nor. 



The same number of the Izvestia contains a paper by M. M. 

 Pomortseff, on hisextremely valuable observations on the direc- j 

 tions and angular speed of motion of clouds. The method I 

 resorted to for these observations is described at length, and the 

 instrument which was used for this purpose is figured on a 

 plate. The chief results are given on 94 separate small maps. 

 The author himself sums up his results as follows : — (i) The 

 middle of the cumulus clouds moves almost in the direction of 

 the isobar which passes through the place of the observer. 

 (2) The cirrus, cirro-cumulus, and cirro-stratus clouds move on 

 a pretty long distance as a broad and nearly straight-line 

 current — the direction of the stream being almost parallel to 

 the part of the 760 mm. isobar which stands on the line con- 

 nectingtogetherthe centres of two nearestand contiguous regions 

 of high and low pressure. (3) There is doubtless a connection 

 between the distribution of atmospheric pressure and the march 

 of the barometer on the earth, and the vertical circulation of 

 the atmosphere ; but this connection does not extend farther 

 than the height of the upper, i.e. cirrus clouds. 



In a letter addressed to the Russian Geographical Society 

 from Lan-chou, in March last {Izvestia, vol. xxix. 4), Mr. 



