106 



METEOROLOGY 



METEORS 



ably dus to this circumstance that ths amount 

 of tha barometric oscillation is liars reduced to 

 the mininiiiiii for :!ia latitude over all anticyclonic 



It has been further shown from tho Challenger 

 observations that the force of the winds on the 

 open sea is subject to no di-tim-t and uniform diur- 

 nal variation, out that on Hearing Ian I the force 

 of the wind gives a curve as pronouncedly marked 

 as the ordinary curve of temperature; the minimum 

 occurring from '2 t > 4 A.M. and the maximum from 

 nnon to 4 P.M. Each of the live great oceans gives 

 th same result the difference- between the hours 

 of least and greatest force being Southern Ocean, 

 GJ miles ; South Pacific, 4] miles ; South Atlantic, 

 i ili-s ; and North Atlantic and North Pacific, 3 

 mil 's. This diurnal peculiarity tif the wind's force 

 i.; even still more pronounced over all tolerably 

 open and extended surfaces of the land. But at 

 tru high-level observatories, situated on peaks, 

 cucll OS Ben Nevis, the reverse everywhere holds, so 

 that the daily minimum velocity occurs during the 

 warmest hours of the day, and tha maximum at 

 night during the coldest hours. 



Tkumderttonni have well -marked periods of 

 diurnal variation over land and over the open sea 

 respectively. In climates where rain falls equally 

 at all seasons they are of most frequent occur 

 rence during the- hottest portions of the day and of 

 tlia year, so far OH coii'-enis the hind surfaces of the 

 globe. Taking Kkatcrinhurg in the Urals as repre- 

 senting in land climates, olwervations show that there, 

 during the twelve hours from !) A.M. to !> P.M. when 

 temperature is almve the daily mean, 717 occurred, 



but only 13D during the other twelve hours wl 



temperature is under the mean. Thus the great 

 majority occur during the time of the day when 

 the ascensional movement of the air from the heated 

 ground takes place, and attain the absolute maxi- 

 mum when the temperature and this upward move- 

 ment are also at the maximum. On the other 

 band, the Cfta/lm^er observation! on the open sea 

 show that the maximum occurrence is from 10 P.M. 

 to G A.M., 22 having IM-CII ol.-ervcd during these ten 

 hours nad only 10 during the other fourteen hours 

 of til-- day. This remarkable result suggests that 

 ovar tbc ocean terrestrial radiation is mora power- 

 ful tlian solar radiation in causing th;>sa vertical 

 disturbances in the equilibrium of tha atmosphere 

 whi 'li give- the thunderstorm. 



AUiiotipheric va|>our ami ascending currents, and 

 tli3 descending currents which necessarily accom- 

 . them, play an Important part in the develop- 

 in 'lit, course, and termination of thunderstorms. 

 WUero the climate is dry and rainless, like that of 

 Jerti-alem in summer, thunder is altogether un- 

 known ; ami where an anticyclone with its descend- 

 ing currents resU OMT a region, as hap|>eiis over 

 tli' centre of the Kuropeo Asiatic continent in 

 win'. , thunder is equally unknown during that 

 season. The diurnal |'riods of hitil, trhirlirinit.i. 

 tPO-tertpoii 'niu, and tnrnmlia have their 



i;\ in Substantially the same atmospheric con 

 ditiiuis as the thunderstorm, and i>ccur approxi- 

 mately at the same hours of the day. 



8e KaemU'n Mrtnir-ititijf ( trmna. 1K45) ; Drew'* Mctt- 

 nr,J.,,,, CM -I. 1*10): ll,rcl>el' JUtl,..r,J..,,, (IHf-M; 

 Kucha,,'. Handy Boole of Mettontmy 

 Trtntttto* Mcttontayw ( 1H68) ; R. H. Moott'. Klnuntary 

 ilttt,*<*i,,1 (1HX3); Mohn'a Klemfntt of Mctrorolo,! y ; 

 H>ni,'n t'linuiti^itiifxl Ail:ii. anil CUmaMm; Bucban'i 

 iiallenger' BcpMliti.,,, i ; 

 >v of Iwlm, lie. The lending poinU 

 ill IK found under uch ' 



MUli.lr 



of thi. wide .ul.jcct wi' 



U :. 

 Anron. 

 IHnmnUr. 



| 



Itaw. 



Omit. 



fenh. 



npontlofl. 

 Krmt 



Hail. 



IUI.KI. 



i*tr. 



. 

 Muni'" 



Rain. 



Snow 

 Slonn, 



. 



ThrniMiiixtcr. 

 W.ii.1. 



Meteors are small bodies travelling in vast 

 niiniliers, and in various directions, through i 

 Our earth continually encounters them in its 

 orhital path, and they ate then revealed to cur 

 observation as aerolites, firclxills, and slumthiif or 

 falling stars. Kvery night, if the sky be clear, 

 some may be observed, on the average (i\e to 

 s.-\i-ii i-M-ry hour, while on certain occasions they 

 are so numerous as to present the s|cctacle of a 

 perfect rain of fire. Besides those visible to the 

 eye. there art' nuinliers unseen, some of which are 

 occasionally noted in the course of telescopic 

 observation. The total num)>cr encountered by 

 the earth in one day has U-en estimated by Pro- 

 fessor Newton, of Vale College. 1'nited Stu't. 

 7,500,000. Their totnl mass, however, he estimates 

 at only UK) tons, so that individually they must in 

 general lie exceedingly minute. They dissipate, 

 however, a quantity of dust in the upper regions 

 of the air, which in its slow de-cent and fall upon 

 the earth is easily detected by pro|>er means. Our 

 air in this case acts as a shield, so that, instead of 

 frequent showers of stones descending with deadly 

 force, we have this quiet falling of impalpable dust. 

 Our conclusions regarding meteors are reached 

 by a proper interpretation of various phenomena, 

 long considered as having no mutual connection, 

 but now grouped coherently under one simplo 

 explanation. In order to appreciate the reasoning 

 which has led to this result, it will be eomenicnt 

 to consider first the observed facts regarding (1) 

 aerolites, (2) fireballs, and (3) shooting-stars. 



The first group, ni'i-ijiti-.t, includes all stony cr 



Hie masses actually falling to the earth from 

 th" sky. They have bean classed as (1) ae'ro- 

 siderites, or sidciitc-. chiefly consisting of meteoria 

 iron ; (2) ac'rosidcrolites, or siderolites, conglomer- 



of stone anil iron; (3) aerolites, almost en- 

 tirely consisting of stone. The common titla 

 aerolites embraces, however, all kinds. Tha 

 descent of such Inxlies, though rare, has occurred 

 with greater frequency than would be imagined. 

 The British Museum alone has specimens of more 

 than three hundred, of which nearly two hundred 

 were seen to fall. Some sacred stones, as tha 

 black stone worshipped at Kuiesa in Syria, the 

 holy Kaaba of Mecca, and the great stone of tho 

 pyramid of Choluhi in Mexico, owed their sanctity 

 to a report, probably true, that they had fallen 

 from heaven. It has l>een suggested that tha 

 earliest image of Diana of the kphc-ians. which 

 'fell down from Jupiter,' had taken the place of an 

 actual meteorite, l.ny mentions the falling of r, 

 shower of stones on the Allan Mount near Rome, 

 about 654 B.C. A Chinese catalogue records tho 

 fall of an aerolite on January 14, 616 lt.c., which 

 broke several chariots and killed ten men. Plutarch. 

 and I'liny mention a great stone, as large as a 

 wagon, tlie lattei s.i>-, and of a burnt colour, tlia 



fall of which, at .Kgospotamos on the 

 about 467 B.C., is recorded in the Parian Chronicle. 

 In 1482 A.D., 'on Wednesday, November 7,'astona 

 weighing 2liO Ib. was si-en to fall near Knsisheim 

 in AlsMM : part of it is still preserved in tho village 

 church there. In 1510 about 1 200 stones, one wt|an- 

 ing 1 2<) Ib., another (SO Ib., fell near Padua i;i lialy. 

 \\ . aie told that the Emperor Jehangir caused a 

 sword to In- forged from a mass of meteoric iron 

 which fell at Jiillunder in the Punjab in 1620. On 

 NoM-mlH-r 27, 1627, the astronomer < .assendi wit- 

 in ied the fall of a stone weighing 511 Ih. at Mount 

 Vaier in Provence. At Wold Cottage, Yorkshire, 

 Decemlx'r 13, 1711."), a ploughman saw a stone of 

 56 Ih. weight fall near him in a field. But the 

 most Interesting of such modern observations 

 was made on April '20, Isn.'l. near l.'Aigle, in 

 Normandy. Aliout 1 P.M. a brilliant fireball was 

 seen traversing the air at a great speed. Violent 



