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266 MONTHLY WEATHER REVIEW. JULY,1896 their direction is suddenly reversed like this, one recognizes that at and heavier air is above, the warmer below. Anywhere in this large least the crisis is half over. I saw very little hail. The occurrence of region tornadoes may occur. Tornadoes are local effects caused by the a violent storm in a city produces any number of strange ha penings, effort to establish a stable equilibrium quickly. They partake of the freaks, and the published accounts of it usually dwell on tgese corn- rotation of the large circular air movement, and revolve, as these do, paratively unmeaning details-freaks-which give no real idea even of in a direction counter clock-wise. Such rotations are produced in the the violence of the wind. large movements by the earth's rotation, but tornadoes are too small * * * to be directly affected by the rotation of the earth. Their rotatory mo- I too; the tirn: to visit,;ersonall;, the ruined parts of the city. The tion is probably determined b that of the genera1 mass of air of which chief damage was done, not b the direct force of the winds out- they form a part. The centrifugal force of their rotation tends to pro- side, but by the bursting of tiehouses from the The hare- duce a vacuum in the center of the tornado. The surrounding air csn metric pressure in the vortex was very low. The pressure the not enter at the sides of the g rating column; it therefore rushes in at It was usually relieved by the hilrst- the and 'lows towar's the center and upwards. In houses was comparatively high. tornadoes the barometer may be about three inches below the normal. ing of the walls and windows. When these were uncomlnonly strong (,4t St. Louis it was about an inch lower.) The local tornado, thus in- the roofs were lifted and, so soon as the pressure was equalized, droi~i)ed ade uately anrl summarilydescribed, is usually less three bun- midrib with ragged portions on each side were left. This in&nce will, Warning Of such a storm can be given by a line Or ''Itside Of a around the dangerous quadrant 1 think, illustrate the force of the wind 8s well as any other. The gyra- ' tory forces were by no means so well marked in this storm as in others (tp a rough pressure-guage, breaks the tele- It was not a typical tornado, though it partook Of ~~~'$$~~~~~~~iUs, that I have studied. pra h wire R,hen the wind blows at a dangerous and the breaking the tornado character. of t\e wire rin s bells wherever one chooses to place them. An ar- * * * * * * rangement of t%is sort was in working order at the Washington Obser- METEOROLOGICAL TBBLES. By A. J. Hamy, Chief of Division of Records and Meteorological Data. Table I gives, for about 130 Weather Bureau stations mechanism, described and illustrated in the Report of the making two observations daily and for about 20 others Chief of the Weather Bureau, 1891-'92, p. 19. making only the 8 p. m. observation, the data ordinarily Table VI11 gives the danger points, the highest, lowest, and needed for climatological studies, viz, the monthly mean I mean stages of water in the rivers at cities and towns on the pressure, the monthly means and extremes of temperature, principal rivers; also the distance of the station from the the average conditions as to moisture, cloudiness, movement river mouth along the river channel. of the wind, and the departures from normals in the case of Table IY gives, for all stations that make observations at pressure, temperature, and precipitation. 8 a.m. and 8 p. m., the four component directions and the Table I1 gives, for about 2,400 stations occupied by volun- resultant directions based on these two observations only and tary observers, the extreme maximum and minimum temper- without considering the velocity of the wind. The total atures, the mean temperature deduced from the average of movement for the whole month, as read from t.be dial of the all the daily maxima and minima, or other readings, as indi- Robinson anemometer, is given for ea& station in Table I. cated by the numeral following the name of the station ; the By adding the four components for the stations comprised in total monthly precipitation, and the total depth in inches of any geographical division one may obtain the average resultant any snow that may have fallen. When the spaces in the direction for that division. snow column are left blank it indicates that no snow has Table X gives the total number of stations in each State fallen, but when it is possible that there may have been from which meteorological reports of any kind have been re- snow o€ which no record has been made, that fact is indi- ceived, and the number of such stations reporting thunder- cated by leaders, thus ( . ). storms (T) and auroras (A) on each day of the current month. Table I11 gives, for about 30 Canadian stations, the mean Table XI gives, for 38 st.ations, the percentages of hourly pressure, mean temperature, total precipitation, prevailing sunshine as derived from the automatic records made by two wind, and the respective depart,ures from normal values. essentially different types of instruments, designated, respect- Reports from Newfoundland and Bermuda are included in ively, the thermometric recorder and the photographic this table for convenience of tabulation. recorder. The kind of instrument used at each station it4 Table IV gives detailed observations at Honolulu, Repub- indicated in the table by the letter T or P in the column fol- lic of Hawaii, by Curtis J. Lyons, meteorologist to the Gov- lowing the name of the station. ernment Survey. Table XI1 gives a record of the heaviest rainfalls for Table V gives, for 26 stations, the mean hourly tempera- periods of five and ten minutes and one hour, as reported by tures deduced from thermographs of the pattern described regular stations of the Weather Bureau furnished with self- and figured in the Report of the Chief of the Weather Bureau, registering rain gauges. 1891-'92, p. 29. Table XI11 gives the record of excessive precipitation at all Table VI gives, for 26 stations, the mean hourly pressures as stations from which reports are received. automatically registered by Richard barographs, except for Additional information concerning the tables will be found Washington, D. C., where Foreman's barograph is in use. in the REVIEWfor January, 1896. Both instruments are described in the Report of the Chief of the Weather Bureau, 1891-'92, pp. 26 and 30. NOTES EXPLANATORY OF THE UmTS. Table VI1 gives, for about 130 stations, the arithmetical Chart I.-Tracks of centers of low pressure. The roman means of the hourly movements of the wind ending with the letters show number and order of centers of low areas. The respective hours, as registered automatically by the Robinson figures within the circles show the days of the month ; the anemometer, in conjunction with an electrical recording letters a and p indicate, respectively, the 8 a. m. and 8 p. m., Unauthenticated | Downloaded 10/06/21 03:50 PM UTC JULY,1896. MONTHLY WEATHER REVIEW. 257 eeventy-fifth nieridian time, observations. The queries ( ? ) ing the depth of rainfall is given on the chart itself. For on the tracks show that the centers could not be satisfactorily isolated stations the rainfall is given in inches and tenths, located. Within each circle is given the lowest barometric when appreciable ; otherwise, a “ trace ” is indicated by a reading reported near the center. A blank indicates that no capital T, and no rain at all, by 0.0. reports were available. A wavy line indicates t,he axis of a Chart, 1V.-Sea-level isobars, surface isotherms, and re- trough or long oval area of low pressure. sultant winds. The wind directions on this Chart are the Chart 11.-Tracks of centers of high pressure. The roman computed resultants of observations at 8 a. rn. and 8 p, m., letters show number and order of centers of high areas. The daily; the resultant duration is shown by figures attached figures within the circles show the clays of the month; the to each arrow. The temperatures are the means of daily letters a aud p indicate, respectively, the 8 a. m. ad8 p. m., niaxinia and mininia and are not reduced to sea level. The seventy-fifth meridian time, observations. The queries ( ?) pressures are the means of 8 a. m. and 8 p. ni. observations, on the tracks show that the centers could not be satisfactorily daily, and correspond to Professor Hazen’s system of reduc- located. Within each circle is given the highest barometric tion ; t,he barometer is not reduced to standard gravity, but the reading reported near the center. A hlank indicates that no necessary reduction for 30 inches of the mercurial barometer reports were available. A wavy line indicates the axis of a is shown by the iiirtrginal figures for each degree of latitude. ridge of high pressure. Charts V, VI, VII, and VIII.-Kite Esperinients at the Chart 111.-Total precipitation. The scale of shades show- Weather Bureau. Unauthenticated | Downloaded 10/06/21 03:50 PM UTC 268 MONTHLY WEATHER REVIEW. JULY,1896 TABLEI.-Clinwlologieal data for Weat& Bureau Slalwna, Pressure in Temperature of the air, in degrees Humidity and preclpi- inches. Fahrenheit. tation. 1 I- Nmw England. Ill 3 63' 0 2' East rt .......... 76 w A5 4:%i$ 0:31 15 5 598 36 e.