164 



NA TURE 



[June 16. 1887 



the Yuen Fu are very fine, presenting a succession of bold out- 

 lines and rocky peaks. A dark-gray quartz-felsite was obtained 

 from a high peak in a range of hills bounding the water-shed of 

 the Min on the south. From the base of the hills a stretch of 

 low flat reclaimed land extends to the coast. The soil of the 

 hills is of a bright red colour, contrasting with the dark tints of 

 the felsitic rocks. 



The fourth group of stations includes a number of localities 

 around Hai-tan Strait. Here the hills present vivid colouring, 

 which contrasts very markedly with the white sands of the shore, 

 especially on Hai-tan Island itself. This consists of three ranges 

 of hills, with intermediate barren plains. Near the north point 

 is a group of reddish sand-cliffs, from 20 to 30 feet high, hori- 

 zontally stratified, and presenting flat summits, which form a 

 miniature plateau deeply trenched by numerous gullies. At 

 the mouth of the strait is a small barren island — Tessara Inland 

 — composed of gneissose rocks, which carry iron pyrites. 

 Slut Island, about 400 feet high, yielded a dark porphyritic 

 felsite, and a weathered surface of the rock displayed evidence 

 of fluxion structure. Syang Point, at Hai-tan, shows granitic 

 rocks running up into high hills. Kiang-shan, on Hai-tan Island, 

 is a hill 1800 feet high, composed of dark-gray quartz-felsite. 

 Mount Bernie, on the mainland, at the south end of the strait, 

 about 1400 feet in height, is composed of a similar rock, weather- 

 ing to a reddish earth ; and in Hungwah Sound the hills are of 

 similar character. In Ockseu, a small rocky island, about 

 twenty miles south of Hai-tan, is a dark-coloured rock, apparently 

 dioritic, and certain masses of this rock when struck, emit a 

 ringing sound, like that of a phonolite. There are here numerous 

 veins of quartz, some showing rather bold crystals, and a good 

 deal of schorl, or black tourmaline. It is notable that the island 

 of Ockseu is especially subject to seismic disturbances. 



THE METEOROLOG V OF INDIA 1 



T T is perhaps inseparable from the mode of issue of the " Indian 

 Meteorological Memoirs" that their titles (e.^^. Vol. III., 

 Part I., I. — Rainfall, Part I.) are rather complex. It is stated 

 that this memoir is to be in three parts, whereof the present 

 part treats only of the normal rainfall of India ; Part II. is to 

 treat of its variations in past years ; Part III. is to contain the 

 tabular data : the whole to form Vol. III. of the series. 



As India depends chiefly on agriculture, the investigation of the 

 conditions affecting its rainfall is of the highest practical import- 

 ance to it. The registers of rainfall available are, except a few 

 private ones, all official work done under Government orders. 

 Some few extend from 1844, but the most of those accepted as 

 trustworthy, after a critical examination, date from about 1S62 ; 

 the discussion includes the data only down to 1883, i.e. covers 

 pretty nearly a complete record for twenty-two years. Alto- 

 gether, the registers of 424 stations are reviewed : for purposes 

 of discussion these are grouped into twenty-five "rainfall 

 districts," i.e. districts with similar rainfall. 



From all these it appears that the average rainfall of the whole 

 of India, excluding Burmah and the Himalya, is about 42 inches. 

 The range of rainfall over this wide area is one of the most 

 wonderful in the world, viz. from about 500 or 600 inches in 

 Cherra Piinji to from I to 5 inches in Sindh, The average annual 

 range over the whole of India (as above) is about 13 in the 

 whole 42 inches. The rainfall is discussed under four heads : — 



(i) Summer Monsoons. (2) Autumn Rains in South-East. 

 (3) Winter Rains. (4) Spring Storms. 



The local distribution of i, 3, and 4 is well shown by tints of 

 various shades on three maps. For the connection with the 

 state of air-pressure, twelve maps are given, showing the isobars 

 for the mean pressure of each month ; the discussion of this 

 connection is c )mplicated, and difficult to summarise. 



(l) Sumtner [South- West) Monsoon. — By some, the south-west 

 mpnsoon is considered to be an extension of the south-east trade- 

 winds, but the author considers their connection to be very 



' "Indian Meteorologxal Memoirs," Vol. III., Part I. I.— The Rain- 

 fall of India, Part. I. Pp. 116, and 9 Plates. A Monograph by H. F. 

 Blanford, F. R. S. (Calcutta: Government Printing Press, 1886.) 



" Indian Meteorological Memoirs," Vol. IV., Part I. Pp. 57, and 4 

 Plates. Edited by H. F. Blanford, F.R.S. (Calcutta: Government 

 Printing Press, 1886.) 



"Report on the Meteorology of India in 18S4," by H. F. Blanford, 

 F.R.S. Pp. 30S and 3 Plates. (Calcutta: Government Printing Press, 

 18 86.) 



doubtful, and gives a rough calculation, showing that the evapor- 

 ation from the Northern Indian Ocean, land of India; and Bay 

 of Bengal is enough to account for the whole of this season's 

 rain. This rainfall is far the heaviest of the four seasons, and 

 the most important for agriculture for most part of India, being, 

 in fact, popularly styled "the rains." On its sufficiency depend 

 the lives of millions. The distribution is at once seen by the 

 tinted map. The west coasts of India and Arakhan catch the 

 first and heaviest fall of over 100 inches : this does not top the 

 coast range of mountains. The next heaviest is from the head 

 of the Bay of Bengal to the Himalya, thence all along the 

 lower Himalya, of from 50 to 70 inches. The amount decreases 

 thence steadily with distance from the head of the Bay of Bengal, 

 and from the Himalya, dwindling to almost nothing on the 

 south-east cor.st and north-west border. 



The effect of a mountain-range in intercepting rain is clearly 

 brought out, e.g. in the Western Ghats this rainfall, coming from 

 the south-west, decreases from 250 inches on the coast to 40 

 inches at 30 miles inland, and to 20 inches at 60 miles from the 

 coast. Again, very little rain crosses the outer snowy range of 

 the Himalya. In fact, it seems to be an established law that 

 the precipitation of rain from damp air is greatest in an ascend- 

 ing current from the chill produced in the ascent, and only 

 moderate in a horizontal current. 



(2) Autumn Rains in South-East. — The author shows that 

 these are not (as often stated) a part of the north-east monsoon, 

 but are, in fact, a late part of the south-west monsoon, corre- 

 sponding to the late and heaviest part of the same on the 

 Arakhan coast. 



(3) Winter Rains. — These are popularly styled the north-east 

 monsoon, and are popularly said to be due to a reversal of the 

 conditions of the south-west monsoon. Their distribution is, 

 roughly speaking, the opposite of that of the south-west mon- 

 soon, and is well shown on the map given. The south-east 

 coasts, which scarcely feel the south-west monsoon, catch the 

 maximum of over 10 inches of this season, the North- West 

 Himalya catch from 5 to lo inches, the head of the Bay of 

 Bengal from 3 to 5 inches, and the rest of the country less and 

 less with increased distance from these places. 



Small as these quantities are (compared to those of the south- 

 west monsoan), they are of the greatest importance to some of 

 the localities named, especially to North-West India, as on them 

 depends the growth of the valuable crops of temperate climates, 

 e.g. wheat, the staple of North-West India ; indeed, in the 

 extreme north-west the winter is the dampest season. 



(4) Spring Storms. — This rainfall is distinguished by increas- 

 ing with the advance of the season, i.e. with the rising tempera- 

 ture, and mainly restricted to the south and east provinces. It 

 is often accompanied by hail and thunderstorms, and is common 

 in the evenings. This rain is usually veiy local, of short duration, 

 heavy, and frequently repeated. 



Altogether, this is a most elaborate and valuable monograph 

 on its subject — the normal rainfall of India. 



Part I. of Vol. IV. of " Indian Meteorological Memoirs " con- 

 tains three memoirs, each a short monograph on its own subject, 

 by different authors : these will be dealt with separately. 



I. — "Account of the South- West Monsoon Storm of May 

 12-17 i" the Bay of Bengal and at Akyab," by J. Eliot (pp. 38, 

 and 2 plates). The history of this storm has been worked out 

 from the meteorological reports of fourteen coast stations, and 

 the logs of fourteen ves-els passing through the Bay of Bengal. 

 The states of the barometer and wind are shown for four days 

 on four charts, and the track of the storm-centre on another. 

 The meteorological conditions seem to have been remarl<ably 

 uniform over the Bay of Bengal for a fortnight preceding the 

 storm ; indeed, this seems to be the normal state of things before 

 a cyclone. The south-east trade-winds seem to have extended 

 north of the equator on May 10 and 11, and gradually advanced 

 into the Bay of Bengal, as strong south and south-west squalls, 

 with rain, increasing in violence within the Bay. In front of 

 these, a barometric depression was foi-med about the 12th, round 

 which, as a vortex, the wind became cyclonic. This cyclone 

 advanced in a curved path north and east (whereas most cyclones 

 advance north and west up the Bay), increasing from 6 miles 

 per hour on the 15th to 15 miles per hour on the 17th, and broke 

 up on the Arakhan Hills close over Akyab on the 17th, doing 

 great damage to property. 



II. — " On the Diurnal Variation of the Rainfall at Calcutta," 

 by H. F. Blanford, F.R.S. (pp. 8, and i plate). This is a 



