526 



NATURE 



{March 28, 1889 



any part of the trunk or main branches of the oculo-motor nerve 

 nor in connection with the branches which pass from the oculo- 

 Tiiotor to join the ciliary branches of the ophthalmicus profundus 

 are there any ganglionic cells ; (5) that the so-called facial con- 

 sists of four separate nerves, the ophthalmicus superficialis, 

 buccal, palatine, and hyomandibular — the last receiving a special 

 bundle of fibres while still in the cranial cavity from the ophthal- 

 micus superficialis; (6) that there are numerous ganglionic cells at 

 the base of the palatine nerve — the nerve which is said to cor- 

 respond to the great petrosal nerve of higher Vertebrates ; 

 and (7) that the lateralis nerve supplies the aural mucous canal 

 as well as the canal of the lateral line. 



In Kaia the following points are brought out, viz., (l) that the 

 ganglion of the ophthalmicus profundus, which is some distance in 

 front of the Gasserian ganglion, lies over the deep branch of the 

 •oculo-motor nerve, from which minute branches pass under the 

 ophthalmicus profundus ganglion to join two or more of the 

 •ciliary branches of the profundus ; (2) that the ciliary branches 

 usually arise from the under surface or outer edge of the ganglion 

 of the ophthalmicus profundus, none of them except on rare 

 occasions springing as in Lsemargus from the trunk in front of 

 the ganglion ; (3) that were the root and trunk of the ophthal- 

 micus profundus greatly reduced in size an arrangement similar 

 ■to that which exists in the higher Vertebrates would be produced, 

 and the ganglion of the ophthalmicus profundus would appear 

 to especially belong, as has often been taken for granted, to the 

 oculo-motor nerve ; (4) that the nerve, generally stated to cor- 

 respond to the chorda tympani of higher Vertebrates, consists 

 chiefly of fibres which spring from the large ganglion at the base 

 of the hyomandibular nerve ; (5) that the ganglion of the lateralis 

 lies several inches (three or four) from the origin of the nerve, and 

 that in addition to supplying the canal of the lateral line the 

 lateralis supplies the dorsal pleural mucous canal, the aural canal, 

 and part of the occipital ; (6) that the five additional ganglia of 

 the vagus complex are disposed as follows, one for each of the 

 four branchial nerves, and one for the intestinal nerve. 



In this preliminary communication the segmental value of the 

 various cranial nerves is not considered, but it is pointed out that 

 further investigations may show that the ganglia in connection 

 with the superficial ophthalmic buccal palatine and hyoman- 

 ■dibular nerves are related to the geniculate, otic, spheno- 

 .palatine, and sub-maxillary ganglia of the higher Vertebrata. 



Physical Society, March 9.— Prof. Reinold, President, in 

 'the chair. —Prof. O. J. Lodge read a paper on magneto-optic 

 rotation by transient currents, with reference to the time required 

 for the production of the effect. If a piece of heavy glass, or 

 tube of carbon bisulphide, be placed between two crossed Nicols, 

 and surrounded by a solenoid, light passes through when a Ley- 

 den jar is discharged through the wire. That the discharge is 

 ■oscillatory, may be proved by turning the analyzer slightly to 

 one side or the other, this having no effect on the result ; or the 

 beam may be examined by a revolving mirror, in which case a 

 beaded band is seen when the discharge takes place. When the 

 •spark itself is analyzed in the same way, a serrated band results. 

 The frequency of the oscillations being given by the formula — 



vii£ 



it is evident that n will be decreased by increasing the capacity 

 S and self-induction L, and this fact was demonstrated by con- 

 necting two condensers, first in series and then in parallel, and 

 placing coils df wire in the circuit. The pitch of the sound 

 ■emitted by the spark was by these means brought within the 

 musical scale. Contrary to expectation, the insertion of a coil 

 with an iron core produced little or no change in the pitch, the 

 reason given being that the induced currents in the skin of the 

 iron wire due to such rapid oscillations of current prevent the 

 interior being magnetized. From the mathematical theory of 

 the brightening of the dark field, it appears that the relative 

 brightness, B, when compared with the light field obtained from 

 the uncrossed Nicols, is given by — 



B = ^ /"'■ sin2 Qdt, 



where t is the time during which an impression can be accumu- 

 lated on the retina, and the angle through which the polarized 

 beam is rotated. When fl is considered small, 



B = l67r2/^2«2 ^^' , 



where k = Verdet's constant, n — number ot convolutions on 

 the solenoid, R = resistance of circuit, and iSV,,- = the initial 

 energy of the static charge. The general solution is given as — 



B 



I 



2mr 



J -^' 



.To(.^) 



dx, 



where m 



= ^. A = Sn/enfiY^ /^, and Jo(x)BesseI 



function. 



Taking the approximate solution, the question as to what is the 

 best size of wire wherewith to wind the solenoid is considered, 

 and as the insulation is very important, it is concluded that the 

 secondary of a Ruhmkorff coil is very suitable. The main in- 

 terest of the experiment is said to lie in the evidence afforded of 

 the practical instantaneity of the development of the rotary 

 property in the substance under examination, for Villari (from 

 experiments made on a glass drum revolving in a magnetic field) 

 inferred that a distinct time, between 1/800 and 1/400 of a second, 

 was necessary, whereas Profs. Bichat and Blondlot, of Nancy, 

 have concluded that the time required is less than 1/30000 of a 

 second. The author finds that carbon bisulphide is able to show 

 the effect when the rate of alternation is 70,000 per second, and 

 has no reason to believe that glass is in any way inferior. As a 

 possible explanation of Villari's results, he suggests that the 

 strain due to centrifugal force would modify the components of 

 the polarized beam, and produce elliptic polarization. Mr. 

 Ward mentioned that experiments similar to Villari's were now 

 being carried out at the Cavendish Laboratory, a disk of glass 

 being rotated about two hundred times per second by means of a 

 turbine. The results so far obtained do not confirm Villari's, 

 but, owing to difficuUies in keeping the speed constant, it is 

 difficult to make exact measurements. It has, however, been 

 found that the strain due to centrifugal force rotates the plane 

 of polarization, and elliptically polarizes the beam ; and that 

 passing an alternate current round a stationary glass bar produces 

 a distinct rotation of polarized light passing through it. Refer- 

 ring to the oscillatory discharge of a jar, Prof. Riicker directed 

 attention to Dr. E. Cook's experiments, described before the 

 Society in June 1888, when photographs showing the dust- 

 figures produced by sparks were exhibited, and pointed out that 

 the frequency required to produce air-waves of the length there 

 indicated was of the same order as the rate of oscillatory dis- 

 charge — viz, about one million per second. Prof. Riicker also 

 wished to know whether glass behaved precisely like CSj- Dr. 

 Lodge said his experiments were not exact enough to decide the 

 latter question, and mentioned that Mr. Chattock had, some 

 time ago, produced dust-figures in tubes by jar-discharges, and 

 shown that the wave-length depended on the capacity and self- 

 induction. Prof. Ayrton suggested the use of a phonograph as 

 a means of recording and reproducing the oscillations, in the 

 same way as himself and Prof. Perry have analyzed the current- 

 curves of alternating dynamos. The discharge could be passed 

 through a small coil fixed to a diaphragm, and placed near a 

 coil through which a steady current was passing, the attractions 

 and repulsions serrating the surface of the rapidly revolving 

 cylinder. By means of a mirror attached to a delicate mag- 

 nifying spring, the section of the surface may be deter- 

 mined. He also inquired whether the experiments shown 

 do prove that the effect is instantaneous. Dr. Thompson 

 remarked that it was satisfactory to learn that Villari's results 

 admit of an interpretation other than by time effect, and 

 thought it advisable to vary the experiment by rotating a bar of 

 glass ; but Mr. Ward said he attempted that experiment four 

 years ago, and abandoned it on account of the enormous speed 

 required. — Dr. Lodge showed some experiments allied to those 

 of Hertz, and pointed out that all the effects were due to reson- 

 ance. The plates of an air-condenser were connected by a wire 

 loop, and placed near a Holtz machine in action. On adjusting 

 the distance between the plates to a particular value, sparks 

 were observed to pass between them ; but, on increasing or de- 

 creasing that distance, the sparks ceased. It was also shown 

 that the sparking was interrupted if the connecting loop was 

 replaced by a coil, though the coil was effective when connected 

 to a condenser of smaller size, thus demonstrating that the time- 

 constant of the condenser circuit was all-important. Another 

 important condition to be observed in such experiments is, that 

 the receiving circuit must be closed, except at the sparking place, 

 so as to permit the surgings of the electricity to take place freely. 

 Other experiments were shown, in which two spheres provided 

 with rods terminating in knobs were used as a Hertz's oscillator, 

 and sparks could be obtained from straight pieces of wire of 



