232 



NATURE 



\yan. 9, 1850 



material in all directions over the plains till vegetation comes 

 and retains it. The uniform character of the pampas loess arises, 

 according to Roth, not from the material and mode of deposi- 

 tion, but chiefly from its transformation under the influence of 

 vegetation. .The roots taking up the matters they need, decom- 

 pose the soil, and the humus arising from the decay of the plants 

 acts on the new material Spread over the surface by wind and 

 rain, along with fresh plants, by way of decomposition. A 

 further metamorphosis occurs by water carrying down matter 

 through the porous layers, with the result of new combinations, 

 and a harder, more compact loess in the lower parts. From 

 observations of marine Tertiary beds of (probably) Miocene age 

 in Entre Rios, over typical pampas loess, Roth infers that the 

 formation of loess began some time in the Eocene period ; in 

 diluvial times it grew in intensity, and has gone on till now 

 without interruption. 



An interesting study has been lately made by Herr Tarchenoff" 

 {Pfliiger's Archiv) of electric currents in the skin from mental 

 excitation. Unpolarizable clay-electrodes, connected with a 

 delicate galvanometer, were applied to various parts — hands, 

 fingers, feet, toes, nose, ear, and back ; and, after compensation 

 of any currents which occurred during rest, the effects of mental 

 stimulation were noted. Light tickling with a brush causes, 

 after a few seconds' period of latency, a gradually increasing 

 strong deflection. Hot water has a like effect ; cold, or the 

 pain from a needle-prick, a less. Sound, light, taste, and smell 

 stimuli act similarly. If the eyes have been closed some time, 

 mere opening of them causes a considerable deflection from the 

 skin of the hand. Different colours here acted unequally. It 

 is remarkable that these skin-currents also arise when the sen- 

 sations are merely imagined. One vividly imagines, e.g., he is 

 suffering intense heat, and a strong current occurs, which goes 

 down when the idea of cold is substituted. Mental effort pro- 

 duces currents varying with its amount. Thus, multiplication 

 of small figures gives hardly any current ; that of large, a strong 

 one. If a person is in tense expectation, the galvanometer 

 mirror makes irregular oscillations. When the electrodes are 

 on hand or arm, a voluntary movement, such as contraction of 

 a toe or convergence of the eyes, gives a strong current. In all 

 the experiments it appeared that, with equal nerve excitation, 

 the strength of the skin-currents depended on the degree to 

 which the part of the skin bearing the electrodes was furnished 

 with sweat-glands. Thus some parts of the back, and upper 

 leg and arm, having few of these, gave hardly any current. 

 Herr Tarchenoff" considers that the course of nearly every kind 

 of nerve-activity is accompanied by increased action of the skin- 

 glands. Every nerve-function, it is known, causes a rise of 

 temperature, and accumulation of the products of exchange of 

 material in the body. Increase of sweat-excretion favours 

 cooling, and the getting rid of those products. 



A METEORITE of special interest to chemists has been exa- 

 mined by M, Stanislas Meunier. It fell at Mighei, in Russia, 

 on June 9, 1889, and it was evident, from a cursory inspection, 

 that it was of a carbonaceous nature. In external appearance it 

 exhibited a deep greenish-black colour, relieved by numerous 

 small brilliant white crystals ; the surface was considerably 

 wrinkled, and blown out into swellings. The material was very 

 friable, and readily soiled the fingers. A section under the 

 microscope was observed to consist largely of opaque matter 

 interspersed with crystals of a magnesian pyroxene and peridote. 

 Fine particles of metallic iron and nickeliferous iron were readily 

 collected by a magnet from the powdered rock, having all the 

 characteristics of meteoric iron. The density of the meteorite 

 was not very high, 2-495. About 85 per cent, of the rock was 

 found to be attacked by acids, the portion so attacked being 

 shown by analysis to consist mainly of a silicate of magnesium and 

 iron having the composition of peridote. On the remaining 15 per 



cent, being heated in a current of dry oxygen gas, it readily took fire 

 and burnt brilliantly. The products of combustion, which were 

 allowed to pass through the usual absorption tubes containing 

 pumice and sulphuric acid and potash, showed that the meteorite 

 contained nearly 5 per cent of organic matter. In order to 

 obtain some idea as to the nature of the carbonaceous substance 

 present, a quantity of the rock was powdered and then digested 

 with alcohol ; on evaporation the alcoholic extract yielded a 

 bright yellow resin, which was readily precipitated from the 

 alcoholic solution by water, and much resembled the kabaite of 

 Wohler. The most curious chemical properties of the meteorite, 

 however, are exhibited with a cold aqueous extract of the 

 powdered rock. The filtered liquid is quite colourless, but 

 exhales a faint odour due to an organic salt which carbonizes 

 on evaporation to dryness, and may be burnt upon platinum 

 foil. The aqueous extract further contains nearly 2 per cent, 

 of mineral matter possessing properties of a novel character. 

 Barium chloride solution gives a heavy white precipitate, which, 

 however, is not barium sulphate. Silver nitrate gives a voluminous 

 curdy reddish-violet precipitate, reminding one of silver chrom- 

 ate, but of quite a distinct and peculiar tint, and which blackens 

 in a very few minutes in daylight. The substance which exhibits 

 these reactions is unchanged by evaporation to drynes s and igni- 

 tion to redness, readily dissolving in water again on cooling and 

 giving the above reactions. The silver nitrate precipitate, when 

 allowed to stand for some time undisturbed in the liquid, be- 

 comes converted into colourless but brilliantly refractive crystals, 

 which polarize brightly between crossed Nicols under the micro- 

 scope, and which are insoluble in boiling water. The properties 

 of this new substance contained in the water extract appear to 

 approximate most closely to those of certain metallic tellurates, 

 but the new compound appears also to differ in certain respects 

 from those terrestrial salts. 



The additions to the Zoological Society's Gardens during the 

 past week include a Brown Capuchin {Cebus fatuellus S ) from 

 Guiana, presented by J. H. Bostock ; a Common Gull (Larits 

 canus), a Black-headed Gull {Lams 7-idibundus), British, pre- 

 sented by Mr. E. Keilich ; two Schlegel's Doves {Chalcopelia 

 piiella) from West Africa, presented by Major C. M. MacDonald ; 

 a Common Barn Owl {Strix flammea), British, presented 

 by Mr. H. Craig; two Swainson's Lorikeets {Trichoglossits 

 novce-hollandiis) from Australia, deposited. 



OUR ASTRONOMICAL COLUMN. 

 Objects for the Spectroscope. 

 Sidereal Time at Greenwich at 10 p.m., January 9 = 5h. 

 17m. 32s. 



Remarks. 



(i) The bright lines so far recorded in the visible part of the 

 spectrum of the Great Nebula in Orion are as follows : — 



Wave-lengths. Observers. 



5872(03) ... Dr. Copeland. 



559 ... Mr. Taylor. 

 520 



500 .., Dr, Hnggins. 



495 



486 (F) 



470 ... Mr. Taylor. 



447 ... Dr. Copeland. 



434 (G) ... Dr. Huggins. 



