384 



NATURE 



[Fed. 19, 1880 



as it was dusk, the star-like object was seen to be accompanied 

 by a great train of light turned towards the east, and estimated 

 by Tycho to be 22° in length ; the head of the comet he judged 

 to be 7' in diameter. Generally he describes the head as round, 

 bright, and of a yellowish light ; the tail appeared to be burning 

 or formed of red rays, brighter and more deeply coloured near 

 the head ; it was also curved, the convexity on the side of the 

 zenith. Tycho's observations with instruments terminated on 

 Tanuary 12, 1578, but he saw the comet for the last time on 

 January 26, and estimated its place with respect to neighbouring 

 stars. 



The orbit of the comet of 1577 was calculated by Halley, but 

 in 1844 a new reduction of Tycho's observations with modern 

 star-positions was made by Dr. Woldstedt, who investigated the 

 most probable resulting elements, in an inaugural dissertation at 

 the University of Helsingfors. 



The definitive orbit is as follows : — 



Perihelion passage 1577, October 26*9476 G.M.T. 



Longitude of perihelion 129 42 - o ) ie »c. 



,, ascending node 25 20"4 ( " 



Inclination 75 9*7 



Perihelion distance 0*1775 



Motion — retrograde . 

 On November 1 when the comet was first seen in Peru, its right 

 ascension would be 230°, with 29° south declination, distance 

 from the earth 0*75, and from the sun 0*28, so that the intensity 

 of light, as represented by the usual formula, would be 21 'S. 

 On the first day of observation in Europe, November 10, at 6h. 

 G.M.T., its R.A. was 266° 19', Decl. - 19° 39', distance from 

 the earth C63, and from the sun 0*53, and hence the intensity of 

 light was 9-1. On November 13, when Tycho detected the 

 comet, the sun set at Uraniburg at 3h. 41m. mean time, and 

 calculating for this time from the above elements, we find the 

 R.A. was 276° 55', Decl. - 14° 19'; the comet was distant from 

 the earth o'647, and from the sun o - 6o4, and the corresponding 

 intensity of light 66, or only one-third of that when it was 

 discovered in Peru, but it was then within 15° from the sun. 

 Saturn was in about R.A. 281°, with 23'' south declination. At 

 the time of Tycho's last observation, or 7I3. 30m. P.M. at 

 Uraniburg, the comet was distant from the earth 2'65, and from 

 the sun 2*07, the intensity of light, therefore, only CV03. A 

 consideration of these figures will amply bear out what we have 

 stated, as to the conspicuous place which the comet of 1577 must 

 claim. 



The Southern Comet.— A second telegram from Dr. 

 Gould, received by Prof. C. A. F. Peters at Kiel the day after 

 the fir*t one, assigns a southerly motion to the great comet, or 

 contrary to that mentioned in the previous one. Both statements 

 may possibly be correct for the times to which they refer, as the 

 ca=e may be similar to that of the great comet of 1843, which 

 sweeping round the sun with a velocity of 350 miles in a second, 

 and almost grazing his surface, passed from ascending tD 

 descending node in two and a quarter hours. 



METEOROLOGICAL NOTES 

 In a "Brief Sketch of the Meteorology of the Bombay Presi- 

 dency in 1878," Mr. F. Chambers opens a discussion of no 

 little importance regarding certain relations subsisting among the 

 meteorological phenomena of India. In that year the rainfall 

 nearly everywhere throughout the Presidency was in excess of 

 the normal quantity, and remarkably well distributed. No long- 

 continued period of unusually dry weather was experienced in 

 any district from the beginning of July to the end of the mon- 

 soon, the year being in this respect strikingly different from 

 1S77 with its drought and terrible famine which followed in its 

 footsteps. From a comparison of the weather phenomena of 

 these two years, it is shown that the abnormal change of baro- 

 metric pressure in July, 1S78, as contrasted with July, 1S77, was a 

 fall of 0068 inch, and the rainfall was 107 "per cent, of the 

 average fall greater in the latter than in the former month ; in 

 other words, the proportionate increase of rainfall corresponding 

 to a fall in the pressure of oico inch, was nearly 16 per cent, of 

 the average fall. It is evident that if the extension of this 

 inquiry to past and future years and to the whole of India, 

 should confirm this important relation between the atmospheric 

 pressure and the rainfall over their extensive region, or establish 

 Marilar relations, the discovery will be of the utmost value in 



assisting towards the formation of forecasts of the probable 

 character of coming monsoons. 



In the same report, Mr. Chambers extends this discussion over 

 a much wider area than that of India, and from a comparison of 

 the atmospheric pressure and rainfall of the Presidency with 

 those at Zika-wei, Manila, Batavia, and Mauritius, arrives at 

 results which, though necessarily provisional in their character, 

 are of the highest importance in the investigation of the great 

 movements of the atmosphere. The general conclusion is that 

 the special function performed by the central area of low 

 barometric pressure in Asia during the summer months is 

 merely that of a distributor of the monsoon vapour by the 

 production of the successive "bursts" and "breaks" of 

 the rainy season ; but that the copiousness or scantiness 

 of the vapour, and consequently of the rainfall, depends 

 chiefly on the meteorological conditions previously existing 

 in the Indian Ocean, the source whence the moisture and 

 rainfall are drawn. The supreme value to meteorologists, in 

 conducting such cosmopolitan inquiries, which attaches to the 

 weather maps of the War Department of the United States, 

 embracing the whole of the Northern Hemisphere, which we are 

 now publishing, is very obvious. Their wide and deep signifi- 

 cance will begin to be better seen on comparing the maps for May, 

 1S7S, about to appear in an early number of Nature, with those 

 for April, which have already appeared (Nature, vol. xxi. p. 

 304). The shifting positions of the areas of high and low at- 

 mospheric pressure, with the consequent or accompanying changes 

 of temperature, will throw much light on the changes of weather 

 which occurred in the different regions of the Northern Hemi- 

 sphere, and their rainfall ; and the maps of subsequent months 

 will go far in the elucidation of such large questions as the rain- 

 fall of India during the monsoon season of 1878, and the 

 exceptional weather we have had in these islands for the past 

 fifteen months. 



One of the most conspicuous services that could be made to 

 science by a simple catalogue of phenomena has just been 

 rendered by Dr. Rubenson, director of the Central Meteorolo- 

 gical Institute of Sweden. The work, which appears in the Trans- 

 actions of the Royal Academy of Sciences of Sweden, is the first 

 part of a catalogue of all the auroras observed in Sweden down 

 to 1877. This part includes those which were observed and 

 recorded from 1536 to 1799. The more special value of the 

 catalogue, in addition to the length of time over which it spread?, 

 consists in the circumstance that it is restricted to a well-defined 

 portion of the earth's surface but of sufficient extent to afford 

 results showing a generally close correspondence to the number 

 ot auroras which actually occurred over that part of the globe. 

 The observations in the earlier years are fragmentary and scanty, 

 but from 1722 the catalogue may be regarded as tolerably com- 

 plete. From 1722 to 1799 auroras are recorded as having been 

 seen on 4,245 nights. These years embrace fully seven sun-spot 

 periods. Arranging the number of days each year on which the 

 aurora was noted, according to the sun-spot periods, we obtain 

 the following highly important results for the eleven years period 

 of sun-spots : 30, 54, 63, 68, 78, 67, 62, 56, 55, 50, and 42. 

 Hence the maximum occurred on the fifth year, there being 

 thus three years from the minimum to the maximum, but six 

 years from the maximum to the minimum. The following 

 figures distribute these 4, 245 auroras, in percentages, through 

 the months of the year : — January, 97 ; February, li'2 ; March, 

 13-8 ; April, S7 ; May, r8; June, o - i ; July, 0/5; August, 

 5-5 ; September, 137; October, 14*6; November, I0"4; and 

 December, icvo. The most rapid increase takes place on 

 August 28, and the most rapid decrease on April 20. 



Mr. William Marriott examines in the Journal oj the 

 Meteorological Society, for October, two series of thermometric 

 observations made for the twelve months ending with March, 

 1S79, the one series being taken with a Stevenson's screen pro- 

 perly exposed on a grass-plot 17 feet square, and the other series 

 with a pair of wall-screens fastened to the brick wall of an out- 

 house with a northern aspect. The results show that the mean 

 of the daily maxima for the year was l°"o lower in [the wall- 

 screen than in Stevenson's screen, but the mean of the daily 

 minima was o 0- 5 higher. The mean temperature by the wall- 

 screen being thus only a quarter of a degree less than that by 

 Stevenson's screen, it is concluded that the mean temperature 

 may be roughly ascertained from thermometers shaded by a 

 wall with a northern aspect. It is to be noted, however, that 

 while Stevenson's screens placed over grass plots well exposed to 





