jMte 17, 1875] 



NATURE 



127 



dates of Herschel's^ observations are given sensibly the 

 same. 



Proper Motion of B.A.C. 793.— Prof. C. P. Smyth 

 has lately drawn attention to an apparent variation in 

 the amount of proper motion of the star B.A.C. 793, 

 shown by the Edinburgh observations between 1837 and 

 1868, involving a diminution in the motion in R.A. and 

 an increase in that in N.P.D. The star is No. 31 of the 

 list included in Argelander's Unterstichun£;en iiber die 

 Eigenbewes^ungen von 250 Sterne?t, Bonn Observations, 

 Vol. viL, Part I., where, from a rigorous discussion of 

 seventy years' observations, the proper motion in R.A. is 

 found to be +012455, and that in N.P.D. , - i'''"456. 

 The comparison of the normal place for i 855*0 with the 

 whole course of published observations to 1865, in which 

 every refinement of calculation is introduced and the 

 above proper motions employed, with Bessel's precession- 

 constants, does not afford any indication of the variability 

 of proper motion suspected by Prof. Smyth. The last 

 Edinburgh observations in 1866 and 1867 show a dif- 

 ference from Argelander's formula of only — o*o8s. in 

 R.A, and agree exactly with the N.P.D. The Wash- 

 ington position, depending upon two observations 

 towards the end of 1870, is in close agreement with 

 Argelander in R.A., and differs — 2"'o in N.P.D. If 

 a position of the star depending upon a good number 

 of observations should be obtained during the present 

 year, the point may be definitively settled, but thus far 

 variation of the proper motion appears to be at least 

 questionable. Upon this subject see Bonn Observations 

 as above, pp. 20, 54, and 109. 



Minor Planet No. 146.— The number of small 

 planets is rapidly approaching otte hundred and Ji/ly. 

 M. Borrelly, of the Observatory at Marseilles, announces 

 his discovery of No. 146 on the evening of June 8. At 

 10 P.M. its place was in R.A. I7h. 20m. i6s., and N.P.D. 

 111° 20' 15" ; it is as bright as stars of the eleventh mag- 

 nitude, and therefore for the present should be readily 

 identified by means of Chacornac's Chart No. 52. 



SCIENCE IN GERMANY 

 {From German Correspondejiis.)] 



HERR VON BEZOLD, of Munich, has published 

 some interesting researches on the periodical 

 changes in the frequency of thunderstorms during long 

 periods of time. These researches are particularly note- 

 worthy for the original manner in which the author has used 

 the statistical materials on thunderstorms which he could 

 obtain (principally within the kingdom of Bavaria). As 

 the character of our reports will not permit us to give 

 details with regard to the manner of treatment, we pass 

 at once to the results which Herr von Bezold has 

 arrived ,at. 



First'of all it was found that the frequency of thunder- 

 storms during a long period is generally either on a con- 

 tinuous increase or decrease, and that these variations are 

 periodical. 



If we ask on which other meteorological phenomena 

 these variations could possibly depend, the first thing to 

 be considered is the temperature. It is further advisable, 

 on account of the numerous relations that have lately 

 been discovered to exist between sunspots and meteoro- 

 logical phenomena, to turn attention also in this direc- 

 tion. It has been found in reality, that if we represent the 

 variations of the frequency of thunderstorms by a curve 

 and compare the same with the curve of the frequency 

 of sunspots, the minima of the thunderstorm curve 

 coincide exactly with the maxima in the sunspot curve. 

 On the other hand, the thunderstorm curve forms, to a 

 certain extent, the mean between the sunspot curve and 

 the curve of the deviation of the average yearly ten^pe- 

 rature for our latitudes. 



We must observe here that although the path of the 

 thunderstorm curve shows a general and unmistakeable 

 connection with that of the sunspot curve (so that, for 

 instance, for the period from 1775 to 1822 the maxima of 

 the thunderstorm curve coincide almost completely with 

 the minima of the sunspot curve), yet the details of the 

 thunderstorm curve coincide better with the details of the 

 curve of temperatures, so that nearly every rise or fall in 

 the latter can be distinctly traced in the former. This 

 connection between thunderstorms and the deviations 

 of the yearly temperatures from the total average, shows 

 itself still clearly, even where that between the thunder- 

 storm and sunspot curves is less apparent. 



Herr von Bezold recapitulates the results of his inves- 

 tigations as follows .-—High temperatures, as well as a 

 solar surface free from spots, cause a greater number of 

 thunderstorms during a year than the reverse. Now, as 

 the maxima in the frequency of sunspots coincide with 

 the maxima of the intensity of aurora borealis, it follows 

 that both groups of electrical phenomena, thunderstorms 

 and aurorae, complement each other, as it were, so that in 

 years with many thunderstorms aurorae will be rare, and 

 vice versd. 



From this connection between sunspots and thunder- 

 storms an immediate electric action between the earth 

 and the sun does not necessarily follow, but it may be 

 simply a consequence of the magnitude of insolation, 

 which depends on the frequency of spots. These changes 

 in the insolation are not felt simultaneously but successively 

 in the different latitudes. The phenomena of thunder- 

 storms, however, do not only depend on the conditions of 

 temperature at a given locality, but also on the state of 

 the atmosphere at far distant points, belonging to another 

 zone ; and this is most evident with thunderstorms accom- 

 panying strong currents of wind or tempests. In this 

 manner the peculiar intermediary position which the 

 thunderstorm curve occupies between the curves of tem- 

 perature and sunspots might perhaps find its explanation 

 eventually. 



In zoological investigations experiments are rare, and 

 therefore the results obtained by them are all the 

 more valuable. The latest work of this kind— " Re- 

 searches on the Theory of Descent : I. On the Season- 

 dimorphism of Butterflies," by Dr. August Weismann, 

 Professor at Freiburg — will, however, interest not only 

 the narrower circle of entomologists, but also the amateurs 

 in this branch of science, as it will furnish them with a 

 sort of guide for the pursuit of their hobbies in such a 

 manner as to do great service to science. Weismann 

 bases his researches on the fact, which has been known 

 for some time, and which has been called "season- 

 dimorphism " by Wallace, that certain butterflies, when 

 issuing from their winter chrysalis in the spring, show a 

 different coloration and design upon their wings than do 

 those which appear in the following summer ; so that until 

 this fact was discovered, the two forms were thought to 

 be two distinct species of butterflies. We will only men- 

 tion one of many examples, as it refers to one of the 

 commonest kinds of day-butterflies. Vanessa levana is 

 only the winter form of Vanessa prcrsa, which is the 

 summer form produced by the former ; the latest offspring 

 of the latter, which survive the winter, reappear as 

 Vanessa levana in the following spring. Weismann ex- 

 posed the caterpillars produced by V. levatia in May, which 

 in the normal state should have produced the imago of V. 

 frorsa, to a continuous temperature of o" — i°C., after 

 they had changed to nymphae. The result was that they 

 yielded the winter form V. levana, with few exceptions. 

 The same result was obtained with the second summer 

 generation, which under ordinary conditions would still 

 have appeared as V. prorsa. On the other hand, Weis- 

 mann succeeded only very rarely in forcing the last 

 generation in the yeariagain to take the Prorsa form, by 

 keeping the nymphae in hothouses at 15°— 30° C, instead 



