206 



NATURE 



[January 2, 1896 



OUR ASTRONOMICAL COLUMN. 



Rotation of Jupiter. — Most of the determinations of 

 the rotation period of Jupiter have been made by observa- 

 tions of surface markings between latitudes 45° N. and 

 35° S. , and little has been known as to the conditions of 

 rotation near the poles. This is due to the fact that con- 

 spicuous and sufficiently definite spots are chiefly confined to the 

 equatorial regions of the planet, and partly to the unfavourable 

 conditions under which the poles are presented to us. Some 

 important observations, however, bearing on the rotation in 

 high latitudes, have been secured by Mr. Stanley Williams with 

 the aid of a 6i-inch Calver reflector (^jA Nack., 3325). On 

 October 10, 1892, a short dusky streak, almost oblong in 

 apjjearance, was observed quite close to the north limb of 

 Jupiter, and reaching at least as far as 85° N. Other streaks of 

 similar appearance were subsequently observed, and frequent 

 observations of the times of mid-transit were made. Confirma- 

 tion of the results has been obtained by an examination of 

 several photographs of the planet taken at the Lick Observatory 

 about the same period, the markings being sufficiently distinct 

 for measurement. Generally speaking, the visual agree very 

 closely with the photographic results, the mean rotation period 

 derived by the two processes only differing by about two 

 seconds. The mean result for the rotation period of the surface 

 material of Jupiter, between north latitudes 40° and 85°, is 

 9h. 55m. 38-93. ± I -208., this being the length of a sidereal 

 rotation expressed in mean solar time. The following statement 

 illustrates the degree of accuracy obtained : — 



h. m. s. s. 



Spot a ... 9 55 337 ± I "32 ( 77 rotations) 

 Spot b ... 9 55 43-8 ± 2-25 (41 „ ) 

 Spot c ... 9 55 397 ± o-6o (252 „ ) 



Mr. Denning's value for a spot in latitude 35° N., namely, 

 9h. 55m. 39s. , agrees very closely with the foregoing, and differs 

 by only a few seconds from the period deduced from observations 

 of the red spot. 



Supplementary details, which are given by Mr. Williams, indi- 

 cate that the positions of markings on Jupiter may be determined 

 with quite as much accuracy from photographs as by the best 

 micrometrical measurements in the telescope. 



The Parallax of o Centauri.— As part of a discussion of 

 the meridian observations of a Centauri, made at the Cape 

 Observatory during the years 1 879-1 881, Mr. A. W. Roberts has 

 deduced a new value for the parallax of this interesting system 

 {Ast Nach., 3324). Mean places for the two components have 

 been computed by applying corrections for proper motion and 

 orbital motion, and assuming a parallax of o"75. The errors 

 of a systematic nature, which cannot be certainly accounted for, 

 are believed to be due to an erroneous value of the refraction 

 depending upon the temperature. Disregarding these, and 

 adopting the aberration constant determined by Chandler, 

 2o"'50, the parallax of o Centauri, from declination measures 

 alone, was found to be o"-8i ± o"'05. From the right 

 ascension measures alone, the value o"-66 was calculated. 

 Solving for both coordinates, the resulting value for parallax 

 IS o"7i±o"-o5. This corresponds to a little over \\ light- 

 years and shows a marked agreement with the parallax o"75 

 found by Drs. Gill and Elkin in 1882 from measures made with 

 the heliometer. 



New Variable Star of the Algol TYV^.—Hat-vard 

 Observatory Circular, No. 3, announces that the star B.D. + 

 I7°'4367. magnitude 9-1, and approximate position for 1900, 

 R.A. 20° 33'-i, Deck -i- 17° 56', is a variable of the Algol type. 

 The change in brightness appears to be rapid, and the range of 

 variation to exceed two magnitudes. 



THE NATURE OF THE PHYSIOLOGICAL 



ELEMENT IN EMOTION. 



pROF. A. C. WRIGHT contributes an interesting paper " on 



the nature of the physiological element in emotion " to 



Brain (parts 70 and 7 1 ), the object of which is to apply the results 



obtained by Gaskell's observations on somatic and splanchnic 



NO. 1366, VOL. 53] 



nerves to the study of the emotions. Prof. Wright begins his 

 paper by taking as an example the phenomena observed in a 

 kitten confronted with a strange dog, and shows that such an 

 emotional stimulus would call forth in the kitten a regular series 

 of reflex responses : first of all, through the involuntary visceral 

 efferent nerves ; then the semi-involuntary muscles, such as those 

 of the face, would be called into action ; and, lastly, there would 

 be reflex response of certain parts of the voluntary muscular 

 system. The essential features to be recognised in this example 

 and in every emotional reaction are — the origination of the 

 emotion in a violent sensory stimulus, a condition of extreme 

 neural tension in the reflex centre, and an overflow of neural 

 energy into different paths. This overflow takes place first 

 into channels associated with involuntary muscle, then into 

 those associated with semi-voluntary muscle, and lastly 

 into those associated with voluntary muscle. The physiological 

 essence of the emotion is to be found not in the visceral reflex 

 actions, but in the high neural tension of the reflex centre which 

 gives rise to these actions. In childhood sensory stimuU call 

 forth in each case responses both of involuntary and voluntary 

 muscle, while with increasing age the outflow of neural energy 

 from the reflex centre becomes more and more restricted to 

 paths associated with voluntary muscle. As a result of such 

 transformation we get purposive voluntary action. The author 

 notices the ^J /r?^r? necessity for some system of control of the 

 reflexes, since "if each minimal stimulus were to evoke a 

 separate reflex movement in an organism which was endowed 

 \yith a sensitiveness at all approaching that ofthehuman organism, 

 life would be a mere chaos of muscular movement." Voluntary 

 muscles react to the slightest stimuli, but involuntary muscular 

 actions are only called out by intense stimuli, or by a summation 

 of slighter ones. High neural tension in the reflex centre is 

 therefore necessary for these reactions of involuntary muscles, 

 and all such high neural tension is attended with a sense of 

 distress. The replacing of the " generaUsed somatico- visceral 

 reflexes of inexperience and childhood by the specialised 

 purposive reflexes of experience and adult life" . . . " is not so 

 much a question of substituting one variety of reflex for another, 

 as it is a question of substituting a condition of low neural 

 tension for a condition of high neural tension." 



PHOTOGRAPHY AND CHRONOGRAPHIC 

 ME A S UREMENTS. ^ 



T N chronographic measurements in physiological experiments, 

 photography has been in constant use for several years, 

 and the methods are well known. I have extended re- 

 cently the method of what may be called photographic 

 chronography to measuring the velocity of projectiles. On 

 former occasions I have shown that to obtain the best 

 chronographic results, magnetic and solenoidal arrangements 

 should be avoided, since by their use a time lag is intro- 

 duced. The following chronographic method depends entirely 

 on light. Two sources of light at a suitable distance apart 

 throw two beams of light on to a sensitive plate, carried on 

 the carriage of a tram chronograph. By means of lenses, the 

 beams of light are caused to form two sharp images on the plate 

 in a vertical line, one above the other ; a tuning-fork trace is 

 also made on the plate ; if the plate traverses, when the beams 

 of light are not interrupted, on development, two black parallel 

 lines appear on the plate ; but if, during the passage of the plate, 

 the beams of light are cut by any solid object which shuts off" the 

 light, then on development two gaps are seen to exist. The 

 distance between these markings when interpreted in terms of 

 the fork trace, give the velocity of the object which cuts through 

 the beam of light. The method was illustrated by allowing a 

 projectile to pass through the focus where the convergent beams 

 of light from two sources of light cross. 



Another method was also shown in which the projectile cut 

 through two thin screens placed in the paths of the beams of 

 light, and so opened a passage for the light. In this case two 

 parallel lines are found on the plate, one longer than the other ; 

 the difference of their lengths, when duly interpreted, gives the 

 velocity of the projectile ; when the distance between the screens 

 is considerable, the beams of light have to be reflected on to 

 the chronograph by mirrors. Frederick J, Smith. 



1 A Note on a Lecture given at Oxford, October Term, 1895. 



