278 



NATURE 



'\Jan. 20, 1 88 1 



The brain-weight of man exceeds that of all animals except the 

 elephant (4500 gr.) and the larger Cetacea; (2500 gr.). The 

 brain-weight of tlie largest apes is hardly a third of man's. Prof. 

 Bischoft^ has worked with a considerable amount of material ; 

 his data comprise the weights of brain of 559 men and 347 

 women. 



PHYSICAL NOTES 



Experiments have been made by Herr G\3x\. {IVied. Ann. 

 No. II) as to the action of gases and vapours on the optical 

 properties of reflecting surfaces. No such influence (expressed 

 in alteration of phases in reflection) is found to exist if the erases 

 and vapours do not act chemically on the surfaces, or are not 

 precipitated in visible quantity (as when the temperature is below 

 the dew point). 



Dr. Fuchs describes a new interference photometer (]Vicii. 

 Ann. No. n) in which no polarisation of the rays at right antrles 

 to each other is required. It consists simply of two similar 

 isosceles glass prisms joined by their basal surfaces, which enclose 

 an air layer varialile in thickness by pressure. A diaphragm 

 reaches out in prolongation of the surface of junction. The 

 observer looks obliquely towards this surface and sees one 

 illuminated surface directly through the double prism, the other 

 by reflection at the air layer. One light-source is fixed, and the 

 other is displaced till the interference bands disappear. 



The polar differences in luminous phenomena of the discharge 

 of electricity through gases «ere considered by Wiedemann and 

 Riihlmann as possibly due, in part at least, to a gas layer (more 

 or less condensed) on one electrode. Supposing that other kinds 

 of envelopes with like action would essentially affect the pheno- 

 mena, Herr Holtz has been able (IVied. Ann. No. II), 

 by covering one electrode, e.g. with silk, or placing a stretched 

 silk disk before ir, to verify this, and almost quite obUterate, in 

 some cases, the polar dilTerences. 



Ik a recent publication describing electrical researches, by 

 Herr Goldstein, in Berlin, that author investigates the phenomena 

 which occur when, in a space so far evacuated that the green 

 phosphorescent light occurs w ith the discharge from the cathode, 

 there are, not one, but several cathodes. He has met with a new 

 form of electrical repulsion, not to be classified either with the 

 mechanical repulsion in collision of ponderable masses, or with 

 electrostatic or electrodynamic repulsion. (An abstract of the 

 memoir appears in Wiedemann's Beihldtler, No. 11.) 



Applying his theory of the potential energy of liquid surfaces 

 to great cycle-operations in nature, M. van der Mensbrugghe 

 {BidUtln of Belg. Acad., 9 and 10) has lately calculated that if 

 evaporation subdivides the liquid of seas into spherules of e.g. 

 l-io,oooth mm. diameter, each kilogramme of water presents 

 a collection of spherules whose total potential enei-gy is equivalent 

 to 450 kilogrammetres, i.e. more than a million times that of a 

 sphere of compact water also weighing i kilogramme. This 

 shows what prodigious quantities of work-units are carried 

 virtually into the atmos| here by h ater vapour, and there is to be 

 added the potential energy acquired by this vapour in virtue of 

 its weight. The author applies his theory to the effects of con- 

 densation, to glazed frost, to phenomena of rivers and waterfalls, 

 &c. He anticipates important verifications of it from the 

 examination of the Gulf Stream in the Gulf of Mexico projected 

 by the United States, and recent soundings have tended to 

 confirm it. 



■ M. MoNTlGNY (Bull. Belg. Acad. 9 and lo) has lately studied the 

 effects of making bells vibrate w ith liquids in them (water, ether, 

 alcohol, sulphide of carbon), or when wholly immersed in liquids. 

 He found that (i) the sound produced was always more grave 

 than the natural sound : (2) that the lowering of tone was more 

 marked in both cases the more dense the liquid (thus it is less 

 with ether than with sulphide of carbon) ; (3) that with all the 

 liquids tried the alteration in sound of a given bell was much 

 more marked when the bell was wholly immersed than when 

 merely filled « ith the liquid ; and (4) that in both cases the 

 lowering of tone was more marked for grave than for acute 

 notes. The general inference is that the rapidity of vibrations 

 of a sounding body is considerably diminished by a liquid with 

 which its walls are in contact, and that this diminution is more 

 sensible when the contact is establL-hed on both sides of the 

 vibrating body than when only on one side. The mode of 

 action is related not only to the density, but to the com- 

 pressibility of the liquid. The lowering of sound is more 



sensible with water than with alcohol and ether; the latter 

 being less dense and more compressible liquids. The form of 

 the bell and the nature of its substance (that is its special elasti- 

 city and Its density) are shown also to affect considerably the 

 pitch of the sound produced in contact with liquids. M. 

 Mo tigny is investigating whether air is a medium of too little 

 density and too great comiwessibility to modify sensibly the 

 duration of vibrations of sonorous bodies. 



At a recent meeting of the Franklin Institute (Journal for 

 December), Mr. Griscom described his new electric motor, which, 

 weighing about 2i pounds, compares favourably w ith those of 

 the old forms of fifteen times its weight. Its most essential 

 advantage is in the field magnets ; the shape of which is such 

 that all the magnetic lines of force, including those nearest the 

 neutral line, are brought into the best possible position for 

 effecting the revolution of the armature. If a bar of soft iron is 

 pivoted at one end to move in a horizontal plane, and a semi- 

 circular magnet is placed concentrically with the circle the bar 

 can describe, then a given force is exerted on the bar at a much 

 greater distance from the poles when the latter is within the 

 semicircle than when it is without. Herein (it is stated), is the 

 secret of the power of Mr. Griscom's motor. The battery is 

 inclosed in a strong waterproof box, gives no odour, and very 

 little trouble in renewing. It is calculated that it will suffice 

 for the sewing of a small family for one year ; a professional 

 seamstress would exhaust it more rapidly, but always in pro- 

 portion to the exact amount of work done. 



A NEW microphone, made by M. Boudet in Paris (La Nature, 

 No. 394), has the general shape of a telephone on a support. It 

 comprises a mouthpiece, in which is an eljonite plate 1 mm. thick, 

 with a short bar of copper penetrating from its middle a short way • 

 into a glass tube in which are six little balls of retort carbon in 

 a row ; a second mass of cipper following the last, and resting 

 on a small spiral spring in a case. The pressure can be varied 

 by means of a screw. The instrument is worked with six Gaiffe 

 elements (peroxide of manganese and chloride of zinc) mounted 

 in tension, and a Bell telephone. It is said to transmit the 

 voice very distinctly without altering its timbre and without 

 aisturbing sounds being produced. 



In a note to the Vienna Academy (,•/«:. December 16) 

 Prof. Stefan describes experiments on the influence of terrestrial 

 induction in development of an electric current, and the excite- 

 ment of the telephone by currents from a rotating coil. The 

 coil used was 56 mm. in external diameter, and 1 1 mm. in 

 width. The earth's influence is best shown by so connecting the 

 apparatus v\ ith a galvanometer that the circuit is closed during one 

 half of the coil's rotation, and broken during the other half ; if the 

 completion of the circuit correspond to the positive maximum of 

 the electromotive force of the earth's magnetism, and the inter- 

 ruption to the negative, the galvanometer is positively deflected. 

 The deflection may be reduced to zero by displacing the contact, 

 and from the displacement and the number of rotations the 

 potential may be inferred in absolute measure. Next the tele- 

 phone was so connected with the coil that the full alternately 

 opposite currents went uninterruptedly through the circuit. This 

 gave a simple tone. With 100 rotations per second the hori- 

 zontal component of the earth's m.agnetism did not suffice to 

 excite an ordinary telephone, but it excited one having a 

 horse-shoe magnet. (When the intensity of the field was doubled 

 the ordinary telephone was also excited.) The tone corresponds 

 to the number of rotations. When the coil was rotated 220 

 times in a second the ordinary telephone sounded. The tele- 

 phone was shown to be less sensitive to currents whose intensity 

 periodically changes than to interrupted currents (an ordinary 

 telephone sounded with 100 rotations or fewer, when the circuit 

 was closed only during a short time of each rotation). 



GEOGRAPHICAL NOTES 

 At the meeting of the Geographical Society on Monday 

 evening a paper was read on the discoveries made by Mr. Leigh 

 Smith last year on the coast of Franz Josef Land, including 

 also a general sketch of the re-t of his voyage in the Eira. Mr. 

 Smith appears to have reached the southern shores of Franz 

 Josef Land with comparative ease about the middle of August, 

 and to have examined it and several islands along a coast-line of 

 over ICO miles of previously unexplored ground. The new con- 

 tinent, as some would fain believe it to be, does not present an 

 attractive appearance, for the coast-line is described as consisting 



