288 



NATURE 



{July II, 187S 



of low pressure and outward from anticyclones, the upper 

 currents blow away from cyclonic and inwards upon anti- 

 cyclonic areas. The most striking part of Mr. Ley's 

 paper is the diagram in which he has summarised with no 

 small amount of skill the facts of his cirrus-cloud ob- 

 servations. The point in the diagram is this : if the 

 upper currents there depicted are tobe regarded as toler- 

 ably close approximations to the movements of the cirrus- 

 clouds of a cyclone, it follows that the region of the cirrus 

 occupies a much higher level over the front portion of 

 cyclone than it does over its rear — notably than over the 

 north-west quadrant — a point of prime importance in rela- 

 tion to the theory of storms. 



The energetic way in which the Missouri (U.S.) 

 weather service is being conducted may be judged of 

 from the fact of the Report of the weather of May 

 having reached us by post on June 24. This Report 

 gives a statement of the rainfall for the month at from 

 sixty to seventy stations, a map showing the distribution 

 of the rainfall over the State for May, and a rapid sketch 

 of the chief features of the weather. The rainfall was 

 greatest in the central-southern districts, amounting to 

 8 "00 inches at Bolivar, and least in the north-east, where 

 at Canton it was only 177 inch. The increased 

 efficiency of the system is well shown by the fulness 

 with which the great storm of the i7-i8th with its accom- 

 panying thunder and lightning and locally-developed 

 whirlwinds has been accurately observed over Missouri, 

 of which Director Nipher promises a full report. A 

 separate sheet accompanies the Report, with all the 

 instances of heavy rainfalls which have occurred during 

 the past thirty years. Of these the most noteworthy as 

 regards rate of fall was a downpour of 5-05 inches in an 

 hour and-a-quarter on August 15, 1848. The heaviest 

 continuous fall was 7 "83 inches during thirty hours on 

 June 18-20, 1859. 



We learn from the Mauritius Meteorological Report 

 for 1876 that the rainfall of the whole island during that 

 year was i2'63 inches less than the average, and that 

 daily observations are now received from Seychelles, 

 Rodrigues, and others of the neighbouring groups of 

 islands. Valuable tables appear in the Report, showing 

 the monthly means of pressure, temperature, and 

 humidity from 1853 to 1874; but the noteworthy feature 

 of the year's observations are the mean hourly values of 

 the velocity and direction of the wind now published for 

 the first time. These exhibit a well-marked daily period 

 in the direction from E. 22° 15' S., the most southerly 

 point at 4 A.M., to E. 7° o' S. at i P.M., and thence back 

 to E. 22° 15' S. at 4 A.M., the daily variation thus being 

 15° 15'. Equally marked is the diurnal variation in the 

 velocity, the minimum 97 miles per hour occurring from 

 2 to 3 A.M., and the maximum i8'5 miles per hour from 

 I to 2 P.M. Hence, as regards this part of the south-east 

 trades, the influence of the sun during the day is to 

 double the velocity of the wind and to impress upon it a 

 more truly easterly direction. 



In an eighth contribution to meteorology Prof. Loomis 

 deals with the origin and development of storms, in which 

 he shows that the great American storms are not confined 

 in their origin to any particular locality, half of them ori- 

 ginating on or close to the Rocky Mountains, and more 

 than two-thirds north of 36° N. lat. The first stage in 

 their development is the formation of an area several 

 hundred miles in diameter, over Avhich the barometer 

 differs little from 30*000 inches, with areas of high baro- 

 meter on the east and west sides, often another to the 

 north, and occasionally a fourth to southward. The 

 mean height of these different high areas examined was 

 30"3io inches on the west and 30 '420 on the east side, that 

 on the east side being thus the greater ; and the distance 

 of each from the central area of nearly uniform pressure 

 which they surround is generally about 1,000 miles. A 



system of winds towards an intermediate or central point 

 then sets in, resulting in a diminished pressure over the 

 central area. The author supposes that the inflowing air 

 escapes by an ascending current, carrying with it a large 

 amount of vapour which as it is cooled is condensed into 

 cloud and rain, and that the heat thus liberated further 

 expands the air, thereby increasing the force of the 

 inward movement of the wind. Rain is thus one of the 

 conditions which increase the force of a storm. Prof. 

 Loomis finds that an area of low barometer of consider- 

 able size may be formed and continue for several days 

 with little or no rain, but in such cases the pressure did 

 not fall so low as 29*250 inches. No storm of great vio- 

 lence has yet been found unaccompanied by a consider- 

 able fall of rain or snow. The general inward movement 

 of the air towards a central area begins before any con- 

 siderable precipitation of rain or snow has taken place. 

 The easterly course of storms is considered to be occa- 

 sioned by the general circulation of the atmosphere in 

 that direction, and by the upward motion of the air 

 taking place principally on the east side of the low centre 

 as indicated by the position of the rain-areas. By this 

 upward motion the air which presses in upon the east side 

 of the low centre is prevented from restoring the equili- 

 brium of pressure upon that side, and thus the low centre 

 is steadily transferred toward the east, or the storm 

 travels eastward. On the other hand, when the fall of 

 rain or snow on the west side of the low centre is copious, 

 widespread, and continued, the easterly progress of the 

 storm is retarded, or arrested, or in some cases even retro- 

 grades to westward, of which the storms of March 9-14, 

 1874, ^nd January 1-18, 1875, were examples. 



Dr. Wojeikof sends to the Paris Exhibition new 

 isobaric charts of the globe for January and July, which 

 are rectifications of Buchan's isobaric charts, published 

 in 1869, made by charting the large amount of fresh and 

 fuller meteorological information collected since that 

 time. Lake Baikal has recently been levelled, and its 

 true height now ascertained to be 1,539 feet above the 

 sea, instead of 1,342 feet, as given by Kropotkine. Cor- 

 recting the barometrical observations for this height the 

 mean pressure of this region in January is 30'63o inches, 

 which is the maximum mean pressure for the globe at 

 this season, and consequently 0*200 inch greater than 

 was given in Buchan's chart. This extraordinarily high 

 pressure in Eastern Siberia, which is i "300 inch higher 

 than that of Iceland at this season, is attributed by Dr. 

 Wojeikof to the clear dry atmosphere of Siberia, and in- 

 tense cold of the valleys and the high mountain barrier, 

 which shuts off all communication, as regards the lower 

 atmosphere, with the Pacific, where pressure in winter is 

 low. A point of some interest brought out in the chart 

 for July is the existence of two centres of low pressure 

 controlling the wind systems of the Asiatic continent, 

 the one being the Punjab and adjacent parts of Belooch- 

 istan, and the other the region around Lob-Nor. Dr. 

 Wojeikof introduces an important feature into his charts 

 in not tracing the isobaric Hnes over those portions of the 

 globe which are at least 1,800 metres (5,906 feet) above 

 the sea, some mountain-groups only being excepted. In 

 this way the great plateau of Tibet, with its ramifications, 

 is omitted, it being evident, for instance, that the winds 

 of the Gangetic plains cannot be influenced by any 

 differences that may obtain between the sea-level pressure 

 there and that of the plains of Siberia, owing to the high, 

 broad plateau of Tibet interposed between. 



GEOGRAPHICAL NOTES 



In the course of the address which he recently 



delivered before the Geographical Society upon the 



subject of his travels on the western frontier of Chma, 



Capt. W. J. Gill, R.E., gave an interesting account of 



