June 20, 1878] 



NATURE 



199 



High winds are also frequent along the dry prairie region 

 bordering on the Rocky Mountains. An interesting table 

 is gfiven, showing the relation between the wind's velocity 

 and the barometric gradients, which may be accepted as 

 rough approximations, but the stations in the United States 

 and in Canada from which the isobaric lines have been 

 drawn, are by far too wide apart from each other to supply 

 the data required in dealing with this important phase of 

 weather. 



Under the heading of a " Brief Sketch of the Meteo- 

 rology of the Bombay Presidency in 1876," Mr. Fred. 

 Chambers introduces some original suggestions re- 

 garding the Indian drought of that year. His method 

 of examination proceeds on the supposition that the 

 droughts of India may be connected with the vary- 

 ing states of the sun's surface as regards tempera- 

 ture, and in the light of the consequences which 

 result from this supposition the observations made in the 

 presidency, from Kurrachee, in the north, to Belgaum in 

 the south, are discussed from which it is shown that the 

 abnormal barometric movements of 1876 were mainly 

 variations in the intensity of the usual seasonal move- 

 ments; and that, as regards the rainfalf, among the 

 causes which produced the drought in 1876, were those 

 very causes which in ordinary years produce a less average 

 rainfall in the eastern than in the western districts of the 

 Presidency. The general conclusion which is drawn, 

 explicitly for the guidance of further inquiry, is that the 

 same principles which explain the usual alternation of 

 the seasons, also explain in a great measure the varying 

 rainfalls of different years. This mode of discussion 

 deserves to be widely adopted in dealing with secular 

 variations in meteorological phenomena, particularly in 

 view of the large scientific issues involved in the relations 

 between the solar and terrestrial atmospheres. 



Prof. Mohn publishes a brief account of the fall of 

 the volcanic ash which was shot up into the air during 

 the eruption in Iceland on March 29, 1875 (Nature, 

 vol. xi. p. 514), and thence carried eastward by the strong 

 westerly winds which then prevailed ; and a map is given 

 showing by curved lines the hours at which the ash began 

 to fall along the extensive track stretching 980 miles from 

 Iceland to Stockholm. The most interesting point in the 

 inquiry is the manner in which the lofty mountain range 

 of Scandinavia appears to have influenced the hour of the 

 fall of the ash. Since the time between the ash leaving Ice- 

 iand and falling on the coast to the east of Stockholm was 

 twenty-seven hours, the mean rate at which it was borne 

 onward was thirty-six miles per hour. During the first 

 twelve hours of its course it drifted eastwards at a uniform 

 rate of fifty miles an hour. It had then approached to 

 from sixty to eighty miles of the mountains of Norway, 

 but thereafter its speed suddenly fell from fifty to twenty- 

 seven miles an hour. The interesting point is that a 

 mountain system such as that of Norway, lying across the 

 wind's path, would appear to exercise a decided influence 

 in reducing the velocity of the aerial current under its 

 level to the extent of nearly one-half, at a distance of 

 sixty to eighty miles to windward. 



OUR ASTRONOMICAL COLUMN 

 The Total Solar Eclipses of May 16, 1882, and 

 August 18, 1887.— There will be two total eclipses of 

 the sun within the next ten years, which may be observed 

 without entailing a long sea-voyage from this country. 

 The first will take place on May 16 (or May 17, civil 

 reckoning), 1882. In this eclipse the central line com- 

 mences in long. 3° 11' W., lat. 10° 40' N. ; totality will 

 occur with the sun on the meridian in 63° 44' E. and 

 38° 35' N., and at sunset in 138^ 51' E. and 25° 25' N. 

 The duration of total eclipse on this occasion is compara- 

 tively short. Probably if observers proceed from England 

 to the central line, they would station themselves in Upper 



Egypt, not far from one ."of the points whence the late 

 transit of Venus was successfully observed. In 32° E. 

 and 2(P 44' N. close to this line, totahty commences at 

 2oh. 32m. 45s, and continues im. los. At a point upon 

 the same, not far from Sherm, at the extremity of the 

 peninsula of Sinai, on the Gulf of Akaba, in 34° 28' E., 

 and 28° 2' N., the duration of totality is im. 17s. The 

 eclipse will be total at Teheran for im. 4s. with the 

 sun at an altitude of 67°, commencing May 16, at 

 22h. 36m. los. local mean time; the central line passes 

 about fifteen miles south of this place. A total eclipse 

 may also be witnessed, though for a few seconds only, 

 near Shanghai. 



The second of the eclipses to whiph reference has been 

 made is the one long mentioned in our popular treatises 

 as the next eclipse that will be total in England, but the 

 central line commences in Germany. The following are 

 the elements — 



1, August 18, at 



S. 



G.M.T. of conjunction in R.A., \i 

 I7h. 14m. 33s. 



R.A. ... 



Moon's hourly motion in R.A 



Sun's „ ,, 



Moon's declination ... 



Sun's ,, ... 



Moon's hourly motion in declination 

 Sun's „ „ 



Moon's horizontal parallax " «..* ~. .." 

 Sun's ,, ,, r i..H<iii ' V; 



Moon's true semi-diameter . 1.. TIT" '.. 

 buns ,, ,, i»»— _»•.'-•• 



The central eclipse begins at i6h. io'2m. in 11° 39' E. 

 and 51° 38' N., and ends in 173° 47' E. and 24° 32' N., 

 and the eclipse is central with the sun on the meridian in 

 102° 15' E. and 53" 46' N. 

 The following are also points upon the central line : — 



[48 7 45'2 

 36 38-2 



2 19*5 

 13 33 lo'i N 

 1254 5*2 N 



9 i3'o S 

 48-8 



60 I2'4 



8-75 

 16 24*4 



IS 48-9 



21 36 E. 

 24 9 

 29 19 



53 50 N. 



54 21 



55 17 



34 15 E. 

 38 23 

 42 I 



56 5 N. 



56 40 



57 7 



It will be seen that the track of the eclipse is chiefly 

 over Russian territory. In the longitude of Moscow 

 and in latitude 56° 33', totality will continue 2m. 30s. ; in 

 Moscow itself the eclipse will also be total, though for 

 about fifty seconds only, commencing at i8h. 44m. 40s. 

 mean time, with the sun at an altitude of 17°. By a 

 direct calculation for Berlin a total eclipse for im. 40s. 

 results, but the sun is barely at an altitude of 3° when it 

 ends. It is likely that a person wishing to view the 

 phenomena of a total eclipse with the sun at fair ele- 

 vation, will find Moscow, or its vicinity, the most acces- 

 sible position ; we will therefore append formulae by 

 v.hich the times of beginning and ending of totality in 

 this neighbourhood, as also the track of the central 

 eclipse, and the north and south limits of totality may be 

 determined, and will also take the opportunity of illus- 

 trating the process by a further example, seeing that 

 many experience difficulty in the application of such 

 formulae. Following the methods described by Mr. W. 

 S. B. Woolhouse in his excellent paper on the calculation 

 of eclipses, transits, and occultations, in the Appendix to 

 the Nmitical Almanac for 1836, with slight change of 

 notation, \ve have from the above elements for com- 

 putation of beginning and ending of total phase at any 

 place not far from Moscow : — 



Cos. w = + 587257 - [i -92757] sin. / + [1*43336] COS. I. cos. (L - 75' 5i'-8). 

 t =i7h. 32.'n. 29-65. =F [1-87565] sin. w — [3-11123] sin. /. 

 — [3 81636J COS. I. COS. (L - 23° 34'-5). 



And for determination of latitude of central line, and of 

 north and south limits of totality in any assumed longi- 

 tude not far from that of Moscow, putting 



« , sin. N = + [1-927571 



n . cos. N = + [1-43336] CCS. (L - 75' Si'-8). 



