AUQUST,1900. MONTHLY WEATHER REVIEW. 333 inches; length of arm from center of axis to center of cup. in summer, is generally eastward or southeastward from some 7 iuches. point north of the Lake region. When the southeasterly When Mr. Hancock gave up observing at the end of 1897. course is pursued the high very often merges with the perma- Mr. C. 0. Plageman removed these instruments to his resi- uent high off the south Atlantic coast, and passes beyond the dence, which is about 200 feet above the sea, and exposed field of observation. In some years. however, the lower lay- them very much in the same way as did Mr. Hancock, the ers of the atmosphere become stagnatecl, and the movement greatest difference being in the anenionieter, which he placed of both highs and lows is sluggish aiid uncertain. upon a platforrri 25 feet above the ground, especially erected The initial movement which led to the hot wave cluriiig for it. Being nom 200 feet above sea, 0.2 iuch was added tc August was the slow drift of an area of high pressure south- the barometer readiiiga to reduce them to sea level. ward and southwestward from southern New York, where it The details of the results of hlr. Haiicock’s and RIr. Plage- wa~located on August 4, to the Ohio and Middle hlissiseippi man’s meteorolngical labors are given in Tuble 3, which it it valleys, in which region it culminatrd ahuut the 8th, in pres- advisable to study in connection with Tahle 1. a# the I~asis Miires ranging froin SO.20 to 30.30 inches. Diiriug the preva- for the latter. In obtaining the de~-poiiitaiid the relative lrtice of high pressures over the eastern half of the United humid~ty,Molesworth’s Psychrometric Tahlps were used. A States pressure was relatively low over the Atlantic south of clay’s wiiicl record began with the ninrniug ohsrrvntion, that the fortieth parallel. is if the ohservatioii was taken at I) a. 111. the miles of wiiid The character of the weather during the heated term, as were counted from 9 a. m. to 9 a. in., and if the oliserv a t‘1011 regards the amount of raiti that fell and the vapor contents was taken at IO a. ni. the mind record \vas counted from 1C of the air, varied greatly. In Kehraska, the Dakotas, and a. ni. to 10 a. 111. RIinnesota great quantities of rain fell. In North Dakota It is unnecessary to enter into a description of the data the average for the State was about fire times the normal. taken from the records of the local ofice of the United Statas The winds were fresh to brisk, mostly slwtherly or sontheast- Weather Bureau, as the iiistrunieiits, method of esposnre and rrly. In Cdorado, Kaiisas, aiid quite geoerttlly east of the reducing, etc , are all kno~vn. It ought to be stated, however. hlississippi, there was a deficieiicy in the rainfall, amouriting that the 8 a. ni. and S p. in. means fur January aiid Februnry. in some States to 75 per cent of the normal. The winds as given in Tahle 1, are those of 1900, and all the other were gentle, and mostly from a southerly qiiarter, except in months, from March to December, inclusive, are those of 1809 certain districts to he nieiitioned later. The periods of ex- It was thonght best to use the January and February iiiraii~ tremely high teiiiperatnre were also times of great dryness, for 1900 hecause the observatiuus were made at 6 a. ni. aiicl tj aid the physical discomfort experienced was not so great as p. m. during January and the first fifteen dnys vf February, would have been the case with lower temperature and higher 1899. The 12 iiooii inems are taken from the Richard haro- humidity. On the other hand it should be remeinbered that, graph traces for 1S99, which are supposed to represent thr almost without exception, the days of inoderate temperature actual readings of the hrometer, therefore 0.03 inch has been mere also days of high humidity, and caused as niuch, if not added to get the sen-level readings. more suffering thau those of very high temperature and low humicli ty. The geographic extent of the hot wave is showii by the THE HOT WEATHER OF AUGUST, 1900. text chart, fig. 3, below. It will he noticed that the warm By ALFRED J. HLNR~,Professor of Meteomlog. weather extended from the hckhone of the Rocky Moun- tains eastward to the Atlantic. The temperature on the In normal sumiiier weather, areas of low pressure (cyclones), monritaiii summits was generally above the nornial, but drift eastward over the northerri third of the Uuited States at throughout the great hasin nnd the Plateau regioii it was irregular iiitervals, generally, however, separated by a period below normal 13s amounts ranging froin 2O to 6O daily. of three or four days. As these lows move across the coiiu- try the districts within their southern and eastern cluadrnuts come successively within the influence of warm south and southwest winds in advance of the cyclone and there results a temporary warni wave. The warm wave is, however, quickly terminated. IJY local rains and thunderstorms. after wliicli the temperature again rises arid the same sequence of events ie repeated. In some years the iiortiial eastward movement uf areas of low pressure (cyclones) is checked ; iii such years they forui ns usual 011 the easteru side of the Rocky Rlouo- tains, or move into the United States from the British Pos- sessions, but instead of drifting eastward persist for days ovvr illontana, the Dakotas, Nebraska, Kansas, C’olorado, and \\‘yo- ming. The barrier to t,heir eastern inovement appears to he the area of high pressure nrhich covers the south Atlantic coast States, and also stretches across the Atlantic to th~ Azores aud the shores of southern Europe. IF’ \A. -.I\! I This area of high pressure is merely a portion of the belt P of high pressure which surrounds the globe having its masi- Fig. 2.-Depnrture from nurinnl tern perattire, August, 1900. mum about the parallel of thirty degrees. It should iiot be Within the general area of high temperature may he found conceived that pressure is uniformly high within this belt. ~mnllareas of excessive heating, as in the nPigh tmrhood of A more accurate conception would be to consider the belt of 5t. Paul and St. Lnuis. The monthly mean teniperatur~for high pressure as consisting of a series of detached areas of 4ugust at St. Paul was 77.2O. a higher averaqe thau has ever high prpsssure separated by trough-like valleys of lower pres- iefore been recorded, and the record goes back to lSd0 (using sure, the whole system having a very slow movement east- ,he Army record made at Fort Snelling). At St. Louis the ward. 4ugust meau was higher than any that had hitherto been The course of areas of high pressure in the United States, ibserved ; the record in this case goes back to 1536.

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~ Additional statistical details are given in the table following: 1 depending somewhat, of course, upon the position of the &m.pccTatiW dola of &mperatur8 a7d, &3tim humidity for Auguet, 1900. center Of the high with resl)ectto that city. In the present __~_ -- - _____ case the center of the area of high pressure which domi- 1 $Ionthly mean, 1 Maximum. I Number of days E:zi$. nated the weather during the days in question was wholly nbove W. ~ per cent. within and over the land area of the United States, viz, to the I-- southwest of Washington. In this position the natural cir- Statlonx. 'g~ culation of the wind in the northeastern quadrant of the high would be from the north or northwest, and such was the case. ti 14 It is but fair to say, however, that the high temperature in - ~- Washington was prim:~rilydue to south and southwest winds on the Gth, yet we litid the rather extraordinary spectacle of Omaha ...... 79.0 Davenport ..... ~Oi9 8 warm, dry northwest~rlywinds and continuecl high tempera- tures for several days in succession, as niay be seen by an St. Paul ...... 1 77.2 inspection of the tahles following. st. LOUIS...... 83.8 The length of time a hot wave will continue is always a Chicago ...... 76.3 10 8 ' 1896 ' HI ti ' tl3.7 iriatter of sonie uncertainty. The conditions that favor its Detroit ...... 1 ;!:; S H 1891 76:B ' + 5.2 Louisville...... 26 ~ 30 ' 1881 , 73.0 1 + 4.- coiitiiinaiice are iiiteiise local insolation, light variable winds, Nashville...... 89.4 25...... 71.8 [email protected] Cincinnnti...... 80.0 15 I8 lHYl T2.2 ~ + 6.9 and possihly the iniportntion of warin, dry air from the trans- Piltsbiirp...... 78.7 12 15 , 1881 li6.6 - 1.7 Mississippi region. Philadelphia.. ...1 79.2 13 10 ~ 1896 63.8 - 2.4 NewTork 76.8 1896 70.8 - 4.1 There is a strong and persistent flow of warm and dry air ..... 8 7 Washington...... 79.6 1 72.6 ~ - 2.S froin the mitlclle Mississippi and Missouri valleys into the

Charlotte ...... 81.9 25 1896 65.2 ~ -13 0 seinipermanent area of low pressure which covers the Dakotas and the nortlirasterii Rocky hloniitain slope during the pre-

25 I 24 ~ 1878 j 89.2 - 0.2' valence of ahnormally hot weather in the Ohio Valley and IS'~~~_____~__ i. I I I the Rliddle States. In its ascent this warin, dry air wob- From the 6th to llth, the period during which the highest il,ly niixes very little with the air of contigucks regions, temperatures of the month were recorded in Pennsylvania, tint flows eastward in the general circulation as a fairly Maryland, the District of Columbia, and Virginia, the winds homogeneous mass of warm, dry air, with temperature and were from a northerly quarter. This apparent anomaly may dew-point considerably above the normal for the season and need a word of explanation. a1 titude. The circulation of air within an area of high pressure, it This wnrni, dry air, flowing easterly in the upper currents niav_. be remembered. is clockwise. In the hot spells geuerally should, according to theory, descend in the region of high ex;erience'd over the eastern part of the Unitid States ouli Dredmre. Ch1or is lent to the theory that it does so descend a portion of the South Atlantic high extends over the land, hy the freedom of the region of high pressure from clouds the center usually being some distance off the coast. The and the presence of dust and haze. The ordinary Washing- pressure distribution in such a case would cause southerly or ton sii~nuiersare free from dust and haze in the upper levels southwesterly winds in the vicinity of Washington, D. C., of the atmosphere, but so soon as a hot spell sets in the air

Fig. 3.--Pressnre carves for August, 1900.

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Fig. 4.--Temprrature cwrves for August, 1000. becomes dusty and hazy; hence we conclude that the hazy development and continuance of B hot wave. The humidity condition is due tu the importation of dust particles from the is not recorded except at 8 a. m. and 8 p. m. and its westward. variations for each hour of the day can not, therefore, be There is some evideuce, fragmentary, it is true, that the given. upper currents, in the level of the higher clouds at least, do The record of the barograph is most interesting; from the not flow constantly from west to east during hot spells as 3d to the 6th an area of high pressure moved from southern uuder normal conditions. On several occasions, during the New York down the coast and spread westward over the Ohio continuance of the hot weather, cirrus and cirro-stratus Valley and Tennessee. It will be noticed that while the clouds were observed moving from an easterly toward a west- high was passing over Washington moderate temperatures erly quadrant. A number of cases of upper clouds moving prevailed, but as eoon as pressure began to fall temperature from a northerly toward a southerly quarter were also oh- hegau to rise, even though the winds were northwesterly (see served. This wou!d indicate, at most, merely a temporary table). After the area of high pressure came the period disarrangement or weakening of the prevailing westerly cur- of high temperature and generally low humidity from the rents in the cirrus cloud level. 6th to the 12th. During this period the skies were mostly Whatever may be the primary cause of the hot wave, it is free from clouds. A few ragged cumuli formed and hung evident that during its continuance the lower layers of the lazily around the horizon, disappearing by sunset. The ba- atmosphere are heated to a much greater altitnde than dur- rometer rose and fell with the regularity of the tide, iudeed ing normal weather conditions, aud a much greater impulse one could almost tell the time of day by the barometer. This is therefore required to overturn existing conditions aiicl rythmic movement of the barometer is best exemplified in bring about rain and cooler weather, thus exemplifying the the calm and tranquil atmosphere of the tropics. old saying, “All sigus fail in dry weather.” On the afternoon of the 12th pressure dropped a little be- We reproduce in the test, figs. 3 and 4 the automatic low the usual afternoon minimum and rain fell the first since records of pressure and temperature at Washington, D. the 2d. The letter R on the barograph sheets indicates the C., for the entire month of August. These instrumeutal occurrence of rain. During the remainder of the month the records enable one to form a clear mental picture of two only baronieter varied but slightly from 30.00 inchee until the of the more important elements which are concerned in the 30th, when a second high approached from the northeast.

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~~ ~ p~ ~ ~~ _____ Haxrmum lamperahcr88 and direction of thwind aa regiatmed by autoinntic Maxiinurn tempericturea and direction of the wind, etc.-Continued. instruments for each ohy of ths period August 2-11, 1900. [Wind directions are expressed in pcrcentageb.] PITTSBURG. PA. UHICAQO. ILL. Perceutage uf the wind blew froin- Percentage of time wind blew from- Max. -___ I1 Date. temn. I 1 I Max. __ -~ Date. temp. N. NE. E. SE. P. PW.

__ ~~~~ ~~ 2 ...... 10 '12 18 ~ 2 42 ...... 43 ...... lp-G-Y s! 6 6 112 33 3 ...... 0% ~ 83 10 1 ...... 1 ...... 1 ...... :a ...... , i 18 53 17 5 4...... , 85 ~ 38 17 16 Y 2 ...... 19 ..... 4...... 94 ...... 42 48 5 ...... j u" I ZI 18 14 1; )i3 )ii 4 21 ...... 5 ...... 94 ...... 12 21 6% ti ...... 9; IS ...... 51 1 6 6 ...... 93 ...... 3% 66 7 ...... ; $15 ' 20 ...... 1 ::::::: ...... ;: ..... : ...... 79 I...... 7 ...... 92 ...... 1: 81 8 ...... 96 31 ...... *, 69 ...... 1 76 9 ...... !Iti 21 79 ..... 8...... na ...... IC 9 ...... 91 ...... A 93 4 ...... 10 ...... 97 I 23 ...... , 1 ...... 11 03 33 1 4 I..... 10 ...... 94 ...... 5 91 4 ...... m.i 43 11 ...... 91 2 ...... 11 ti5 Averages ...... I...... 49.2 1 5.5 3.2 1 3.1 1.7 3.3 I 5.3 ~ 49.1 1 0.6 Averages ...... 0.6 3.6 2.4 7.4 16.3 62.0 __ I

~~ ~~

~ -~ I a ...... ~ 71 3 I..... 11 3 2...... 3 ...... 1 78 31 5 ...... 1 1:::::. 3...... I...... 4 ...... 81 11 i 36 I 34 11 3 ...... 4...... 1 ...... , 5 ...... 94 ...... 1 26 1 59 14 ...... 5 ...... 6 ...... 1 93 ...... PO :...... 6...... 7 ...... 9% ...... 25 ...... , ...... 8 ...... l9t ...... 45 55 ...... 8...... ~:::::. 9 ...... 190 ...... I...... 56 41 ...... 9...... 10 ...... 93 ...... I...... 1 81 19 ...... I ..... 10 ...... It...... 99 I ...... I 75 25 ...... 11 ...... ~5...... I Averages.. ... 1 ...... 1 2.51 5.21 4.81 4.21 7.71 53.6 21.6 0.4 ...... Averages ...... 9.4, 40 1.5 6.7 10.5' 1.3' 14.4, 50.7' 0.5 I

NOTES BY THE EDITOR.

WEATHER BUREAU MEN AS INSTRUCTORS. A.-ESTRA('T$ FKCIM LAST ANNUAL REPORT OF STATIONS. It has long been evident that meteorology is but too slowly P. C~niior,Local Forecast Oficial, Kansas City, Rlo.: makiug its way into uiiiversities and colleges as a11 important The sn1)ject of ~nrteornl~~gyl!as been kept before the cnmmunity branch of study. Some prcigrtcss has been achieved in the quite prominently. Tlie vilirial in charge Ilelivered a discourse Ibefore public schools where meteorology is sonietimes taught iude- one of the high schools, and rrad a pal'er entitled: " The weather- pendeutly but more frequeiitly as a branch of physics or as something regmliiig its make up ani1 efircts," before the Commercial an essential part of physical geography. It has long been ('lub, at, the dicitntion of t1i:it bogly. Bnother paper was prepared (and approvet1 by the Central (.Mice) to be reall before the Acdemy of known that the Weather Bureau observers and oficinls have Sciences tonwil the close of the year, but the alrsencefrorn tlie rity of done all that they could do, consistently with other duties, several of the more 1wtJiuinent members, suggested the atlvisability of to supply the demand fur instruction and to dissipate the hol~linpit for a future occasion. ignorance that prevails in mauy minds by reason of which The central high school ha< atloptetl meteorology in its curriculum, and niatle it one of the elective sttulieh. The first clufis was formetl meteorology has been associated with astrology, folklore, (luring the winter ancl nunil~eretlabout 25. Next year a larqe class is animal instinct, and other obscure, if not unscientific, fields anticipated. The class and teacher have visitell this oHice to see the of thought. practical siile of the su1ijec.t. There is no better method of learaing all that is k110wii Maps an41 R eather information generally have been eagerly soapllt by scliools in Kansas and webtern Rlissouri, ani1 many teachers from about a given subject than by undergoing the lalior involved those States have visited this oftice. in preparing ct lecture thereon, either for the puldic or for the college student. To do this successfully one must follow 8. W. Glenn, Local Forecast Oficial and Section Director, thn Roonnion rnla hn mnnt rnnrl in nrrlnr tn hnt-nnla fnll hn Huron. S. D&.: order to become fluent. Of the many lines of work by which weather maps were given to the local Iiigh schuol class in physics, a11d the members of the itreather Bureau service iiiay henefit the by mutual anderstan~linpIretween tlie official in charge ani1 the presi- dent of the State Agricultural College, the students of tliat inbtitution service and the country, we put the ability to lecture and in- vibit the office singly and in numbers for instruction in meteorology. struct in the front rank dongside of the ability to make bet- ter forecasts, or long-range forecasts, or to invent devices for T. E. Jennings, Section Director, Topeka, lians.: prevention against damage by hail, frust, wind, and other In February last I tleliveretl an address, by invitation, before the meteorological elements. Farmers' Institute at Berrytoan, this county, on the Unitell States The Editor conceives it to be quite iniportant that the Weather Bureau in its relation to agricaltaral interests. members of the service should stimulate each other in this In November, January, ant1 March, I lectured before the teachers' To association of this city, treating of the composition of the atmosphere, good work. this end he has compiled tlie following ex- its changes in weight, temperature, and moisture, its general ancl acci- tensive collection of abstracts from both the annual reports dental movements, instruments for measuring ita weight, temperature, of the respective stations mid especially from the replies to moisture, and movements, esl)lanation oftlie instruments, the I' lbhoto- a special circular letter of July 14, 1900. These abstracts grajrhing" the conditions twice llaily by means of synchronous obser- vationti chartetl on maps, and the construction of such a map from a are generally in the exact words of the origiiial replies, tlie bulletin published in one of the Chicago (lailies. few changes that have been made being necessary only for In June such a lecture was also delivered before the County Teach- greater perspicacity. ers' Institute at the High School Building.

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