i6 



NA rURh 



[November 4, 1897 



OUR ASTRONOMICAL COLUMN. 



The Photography of Faint Moving Celestial Objects. 

 — An ingenious but simple method of photographing unseen or 

 very faint moving but known celestial objects has recently been 

 suggested by Prof. Barnard {Astr. Nachr. No. 3453). Every 

 one knows that in order to photograph a faint celestial object, 

 it is only necessary to prolong the exposure until a suffi- 

 ciently burnt-out image is recorded on the photographic plate. 

 If, however, the object has a rapid motion, then the image will 

 not remain on one part of the plate a sufficiently long time to 

 record its impression, since the clockwork of the instrument is 

 regulated to counterbalance the apparent motion of the stars. 

 Prof. Barnard's idea is to use, in the eyepiece of the guiding 

 telescope for following the object in question, two guiding cross" 

 wires attached to a light frame which can be moved by a delicate 

 clockwork (the works of an ordinary watch are sufficient), the 

 speed of which can be regulated to the motion of the object. 

 Arrangements can also be made that its direction of motion can 

 be regulated to any position-angle. When adjusted to the eye 

 end of the guiding telescope, the instrument is set so that the 

 amount and direction of motion of the cross wires shall coincide 

 with that of the comet or minor planet. 



A star in the field of view is then bisected by the cross wires, 

 and the mechanism set in operation, the star being kept bisected 

 by the ordinary slow motions for star guiding. It will thus be 

 seen that although the operation is exactly the same as if the 

 star itself were being photographed, it is the image of the comet 

 which will remain stationary as regards the photographic plate, 

 while the stars will produce trails. Prof. Barnard mentions 

 that the device will be very serviceable for photographing 

 visible comets with ill-defined nuclei, as these have no definite 

 points to guide by, and it is for this work that he is going to 

 have an instrument of this kind made. 



Sunspots and the Weather. — Although nearly every one 

 is agreed that sunspots do influence our weather, the relation 

 between them is evidently not a very simple one. Statistics of 

 the weather from places situated in moderate latitudes do not, 

 at any rate, bring out very clearly direct indications of such a 

 connection ; but when they are gathered from a large region 

 near the equator, such as India, then the effect of the sunspot 

 cycle on the weather is more decisive. The first effects of solar 

 disturbances would be felt at the equator, and as the mean 

 temperature does not vary very much from the extremes, a 

 general small increase or decrease would make itself apparent. 

 In more northern latitudes local disturbances seem to tend to a 

 great extent to mask the effects of a variation in the amount of 

 solar radiation. 



Mr. Alexander MacDowall has, however, examined a number 

 of weather statistics from several European stations — viz. Bremen, 

 Paris, Geneva, Greenwich — and he finds that they are suggestive 

 of a relation to the sunspot cycle (Quarterly Journal of the 

 I^oyal Meteorological Society, vol. xxiii. No. 103). 



In making out his curves he says he has used smoothing 

 methods freely, sometimes smoothing with averages of five and 

 sometimes with additions of five. In this investigation the 

 author has compared corresponding portions of successive years, 

 such as the winter half, summer half, the four seasons, &c. To 

 sum up the inquiry in his own words, he says : " In the climate 

 of Western Europe there is apparently a tendency to greater 

 heat in the summer half and to greater cold in the winter half 

 near the phases of minimum sunspots than near the phases of 

 maximum ; the contrast between the cold and heat of the year 

 thus tending to be intensified about the time of minimum sun- 

 spots. ... If we accept the view to which direct observation of 

 the sun seems to lead, that solar radiation of heat is greater 

 about the time of maximum sunspots, we appear to have a direct 

 explanation why, on the one hand, our winter cold should thus 

 be moderated ; and as to the contrary effect in the summer half, 

 it is not difficult to conceive that solar activity may, by increased 

 evaporation, bring about the presence of more cloud, and so 

 give us cool, rather than hot, summers." 



The conclusions drawn by Mr. MacDowall are exactly what 

 would be expected, and they corroborate those that were formed 

 many years ago. Thus, for instance, in a pamphlet published 

 in 1879, and submitted to the Indian Famine Commission, we 

 read : " For it is an acknowledged and readily accountable fact 

 that presence of cloud in the summer is associated with coolness, 

 and in the winter with warmth ; and in like manner that a clear 

 sky, which in the summer, by promoting solar radiation, favours 



NO. 1462, VOL. ^J^ 



the development of great heat, in the winter, by giving free 

 scope to terrestrial radiation (in the then comparative absence 

 of solar radiation), tends to produce excessive cold. The fact, 

 therefore, that clouds are more prevalent in the summers of 

 maximum sunspot years, and in the winters of minimum sun- 

 spot years, is only another way of saying that both summer and 

 winter are cooler at the former epoch and warmer aX. the latter." 



Comet Perrine, October 16.— The following is a con- 

 tinuation of the ephemeris of this comet, computed by Herr. J. 

 Moller (Astr. Nachr., No. 3454) from the observations of 

 October 16, Mount Hamilton ; October 18, Strassburg, and 

 October 20, Hamburg (two observations). 



1897. 



R.A. 



\2h. Berlin M.T. 



Decl. log r. 



log A. 



Nov. 7 ... 19 25 54 ... -f75 21-9 



8 ... 15 59 ... 74 19-4 



9 ••• 7 31 ••• 73 170 



10 ... 19 o 19 ... 72 15-0 



11 .. 18 54 10 ... 71 14-0 

 . 12 ... 48 51 ... 70 14-1 



13 ... 44 13 ... 69 15-4 



14 ... 40 10 ... 68 i8-o 



15 ... 36 36 ... 67 22-Q 



16 ... 18 33 30 ... -f 66 27-5 ... 0-1456 



The following comments relate to the appearance of this 

 comet : — 



Karl Mysz : 6-inch refractor in Pola. October 18, comet 10 

 mag. ; axis of tail, 200° ; nucleus appears sometimes double or 

 oblong. October 19, same appearance and brightness as yester- 

 day ; nebulosity has diameter of 5'. 



J. Moller : 8-inch refractor in Kiel. October 20, nucleus 

 iO"3 mag., oblong and hazy; fan-shaped tail of about 2' in 

 length, having a position angle of 200°. 



Schorr and Ludendorff" : Hamburg refractor. October 20, 

 comet has faint nucleus, io"5 mag. ; tail, o''5 towards south. 

 October 24, fainter than October 20 ; no distinct nucleus. 



Picart : at Bordeaux, October 20. The comet has a very 

 feeble tail ; its general form is that of an elliptical nebula. 



The Director of the Lick Observatory. — We regret 

 to read in the Astronomische Nachrichten (No. 3454) that, after 

 a continuous connection with the Lick Observatory for twenty- 

 three years, and a service at Mount Hamilton since the year 

 1888, Prof. Holden has resigned his post, and will terminate 

 his official relations with the Observatory December 31, 1897. 

 His address after October i will be Smithsonian Institution, 

 Washington. 



RELATION BETWEEN INDIVIDUAL AND 

 RACIAL VARIABILITY} 



ly/TR. BREWSTER'S memoir refers to "allied races" with- 

 ^^ out defining that phrase, but apparently basing it on the 

 idea of divergent races sprung from a common source. The 

 mean (or typical) characters of these races differing from one 

 another, as individuals of the same race diff^er among them- 

 selves, two systems of variables exist in respect to each and 

 every character : (i) a single system, referring to the means of the 

 different races ; (2) several separate systems, referring alike to the 

 individual values of the same character ; in each and every race. 

 He supposes the ordinary law of frequency to be approximately 

 applicable to both systems, so that the peculiarities of every 

 series admit of being roughly expressed by its own mean and 

 quartile ( = probable error). In order to reduce the variability 

 of each series to a common scale, he works, not with the ob- 

 served quartiles, but with what may be called reduced quartiles, 

 namely the indices formed by dividing each quartile by its cor- 

 responding mean. These being comparable on equal terms, are 

 his "measures of variability." 



The first and more important part of the memoir deals with 

 eighteen different characters in eight human races, the data 

 being derived from '^€\?\yasi^s Kdrpermesstmgen. The number 

 of individuals in each of the selected races is unfortunately very 

 small, ranging from eight to twenty-six, though he is able to 



1 " A Measure of Variability and the relation of Individual Variations to 

 Specific Differences." By Edwin Tenney Brewster. {Proc. Amer. Acad. 

 Arts and Sciences, May 1897.) 



