326 



NA TURE 



[JANUARY 31, 1895 



aboot r in 250 feel, in the first 4000 feet, which is noteworthy, 

 iS the se» surface causes less diminution with height. Above 

 4000 fee!, clouds were encountered, and these changed the rate 

 of diminution, while at the highest 'point, the result was V in 

 400 feet. The most interesting feature is the gre.it dryness of 

 the air above 7500 feet ; at 6000 feet the relative humidity was 

 100 per cent., and at iSoo feet higher it was only 4 per cent. 

 Prof. Hazen states that this is the ra^st extraordinary fall in 

 humidity ever observed, and it shows how little we really know 

 of atmospheric conditions, even at very low heights. The value 

 of the results to be obtained by balloon ascent; in determining 

 the laws of storms is beyond doubt, and Prof. Hazen strongly 

 advocates that such researches should be undertaken. 



The origin of the .\lpine Serpentines has always been a 

 subject for wide differences of opinion. The Italian school of 

 geologists until lately upheld the view that they were metamor- 

 phosed sedimentary rock-!, while English and German geolo'^ists 

 maintain their intrusive nature. O.ie of the latest contributions 

 to this subject comes from Dr. Ernst Weinschenk who, in the 

 Abhandtun^en of the Bavarian Academy of Sciences (Munich, 

 1891) describes the occurrence and petrography of the serpen- 

 tines of the Great Veneiiger, a mountain in the Eas'ern Alps of 

 North Tyrol. He tinds that -they are undoubtedly intrusive 

 rocks, formed by the consolidation of a peridotite magma that 

 wa» squeezed in between the foliation-planes of the neighbour- 

 in;; mica-schists during the great Alpine earth-movements. 

 They thus occur as a series of laccolites (/jw.v/;), which, we 

 mav observe, resemble in their origin those i)f Shropshire rather 

 than the typical laccolites of the Henry Mountains, which were 

 intruded into horizontal strata. After their first consolidaiion, 

 the peridotites were crushed by the continuation of the earth- 

 movements, and by the continued action of superheated vapours 

 and solutions were gradually converted into their present con- 

 dition. The evidence of these changes is seen in the minute 

 structure of the rocks, which, as well a; the nature of the 

 melamorphism they have produced in the surrounding schists, 

 is eichausiively described in the paper, and illustrated by a 

 number of micro-photographs. 



deals with the gneiss 

 These have also been 



A SECOXt) paper, by the same author, 

 and granite of the same part of the Alps, 

 studied by Prof. L<i«l, whose results are published in the 

 Verlaf;der k.h. ^eol. Mcichsaii^lall {\"\enn&, 1894). Thisauthor 

 treats the subject from a sirucluril point of view, and his 

 memoir is illustrated by a map and several sections ; while Dr. 

 Weinschenk describes the petrography in detail. Both authors 

 assert the undoubtedly intrusive origin of these rocks, and 

 incline to class them with the pre-carboniferous " Prologine " 

 of the Western Alps. Dr. Weinschenk regards certain 

 peculiarities in the granite as due to lateral pressure during the 

 period of consolidi'ion, and proposes the term I'iezocryilal- 

 litalian for the development of structures under such conditions. 



TilP. elasticity of solid gelatine solutions is the subject of 

 an investigation by Erwin Fraas, in Wiedemann' s Annalen. 

 Sticks of aqueous gelatine were obtained in the following 

 manner. Brass tubes, about a foot long and half an inch thick, 

 were cut in two at the centre and joined by wire rings. They 

 were closed at one end with a cork, and were placed vertically. 

 The gelatine solutions were then poured in, care being taken 

 to prevent adhesion by rubbing with olive oil. The suspension 

 of the slicks was a matter of some difficulty, but it was accom- 

 plished by brass clamps of the shape of a cylinder, cut along 

 ill length on Imth sides and roughened inside, which were 

 gently pressed on the gclaline by a spring. It was found that 

 io no case did the volume change by stretching, the diminution 

 girth lieing compensated by the increase of length. The 

 NO. I318, VOL. 51] 



addition of common salt impaired the elasticity and strength ot 

 the sticks very considerably, making them unlit to support a 

 pound -weight, while part of the water could be replaced by 

 glycerine, cane sugar, or gum arabic, without making any 

 difference. 



Thi; Comples-rendiis of the Paiis Academy, of January 14, 

 givean account of some modifications of anelectrical anemometer 

 for metly used by the Rev. Marc Dechevrens, at Zi-ka wei, for 

 recording the horizontal and vertical movements of the atmo- 

 sphere. The instrument, which is being constructed by M. 

 Richard, is to be erected at the observatory of the Jesuit College 

 in Jersey, and possesses some novel contrivances intended to 

 ensure its satisfactory performance. The fan of the anemometer, 

 which gives the horizontal component, is formed by portions of 

 a cylinder ; this arrangement was devised hy M. Dechevrens, 

 and is said to give excellent results. There is also an arrange- 

 ment which assures sufficient duration to the electric contacts, 

 to excite the electromagnets, while preventing prolonged 

 contacts, which exhaust the batteries without doing any good. 

 Two wires out of seven which exist in similar instruments are 

 dispensed with ; this is also an important simplification if the 

 registrations are to be recorded at a distance. 



The current number of Wiedemann's Annalen contains a 

 paper by Max Weber, on electromagnet pull. The author has 

 measured the pull exerted on a long iron wire, one end of which 

 projects within a helix, when a known current flows through 

 this helix, producing a magnetic field of known intensity. The 

 wire under examination is suspended horizontally by four silk 

 fibres in the same way as in a ballistic pendulum. The dis- 

 placement of the wire under the action of the coil is meavured 

 by means of a microscope, and from a knowledge of the weight 

 of the wire and the length of the suspending fibres the pull can 

 be calculated. Ihe author has investigated the connection 

 between the pull per unit cross-section of the wire {/„), the 

 strength of the field within the helix (H), and the intensity of 

 magnetisation (J), and finds that/,, = JH, when the length of 

 the wire is parallel to the lines of force of the helix, and the 

 diameter of the wire is very small compared with its length. 

 The author has also examined the pull perpendicular to the 

 lines of fore?, by uslnj two coaxial magnetising coils separated 

 by a small interval, the wire being placed with its length per- 

 pendicular to the axes of these coils, and its end passing through 

 the space left between them. If the pull per unit area of cross- 

 section of the wire under these conditions is called/j., then 

 /± is always, in the case of iron, less than/,,. For fields having 

 an intensity ol a')out too, the ratio ///J- is about 100, but 

 decreases rapidly with increasing field strengths, and appears 

 to approach unity as a limit. Thus for H = 1 2,000 /„/± =I'II. 



It is known that the direction of the pendulum line shows a 

 consideiabic anomaly around .Moscow. The line is deviated at 

 Moscow by lo"'6 to the north ; at Tsaritsino, in the south-east, 

 the deviation is only o '5 in the same direction ; and at Podolsk, 

 which is twenty-one miles from the capital, the deviation takes 

 the opposite direction, to the south, and auains - 2" "J. It has 

 been supposed that beneath the neutral zone, at Tsaritsino, 

 there must be great cavities in the rocks, or that the rocks, 

 as a whole, have a density below the average. We now learn 

 from a note by (General Stcbnitskiy, in the last issue of the 

 /zveslia of the Russian (Geographical Society (1K94, No. 4), that 

 the pendulum observations which have been made around Mos- 

 cow by M. Iveronoff, give full support to the above supposition. 

 The differences between the lengths of the second-beating pen- 

 dulum, observed and calculated, being positive at .Moscow and at 

 Podolsk ( -f 00108 and + 00064 millimetre-^ respectively), the 

 same difference is negative above the neutral z>ne uf Tsaritsino 

 ( - o°o228 millimetres), thus showing a deficiency in the acceieia- 



