Od. 



lO. 



1878! 



NA TURE 



6?i 



THE WEATHER CASE, OR FARMERS' 

 WE A THER IN Die A TOR • 



Description 



STAND facing and look at the weather case. Now : 

 The right of the case is at your right hand ; the 

 left of the case is at your left hand. 



The pointer or index at the top of the case (No. i) 

 slides on the brass arc; it is known as the "Sunset 

 Barometer Index," and indicates, when set by the figures 

 to which it points on the "Main Barometer Scale," 

 which is just below it, the reading of the barometer at 

 the time of the sunset yesterday. 



The " Main Barometer Scale" (No. 2) exhibits all the 

 barometric readings likely to be used with this in- 

 strument. 



The pointer (No. 3) just below the "main barort>eter 

 scale" is called the "mean barometer index," and indi- 

 cates, when set, the mean or average reading of the 

 barometer at the place at which the instrument is set and 

 for each separate month. When the barometer reads 

 above or below this reading at any place, such reading is 

 said to be "above the mean " or " below the mean" for 

 that place in that month. This index is set once for each 

 month in the year. 



When the barometer pointers go toward the right from 

 this mean or average reading, the barometer is said to be 

 "rising." When the barometer pointers go toward the 

 left from the mean or average reading, the barometer is 

 said to be "falling." 



The mean barometer reading for each district for each 

 month is stated in the Farmers' Bulletin, or can be had 

 by application to this office. 



The long brass hand over the glass face of the baro- 

 meter is known as the " long pointer," and indicates, by 

 the figures of the "main barometer scale "to which it 

 points when set, the reading of the barometer when last 

 set. 



The black pointer on the face of the barometer under 

 the glass face is known as the "short pointer, and indi- 

 cates the existing pressure of the atmosphere at any time 

 the instrument may be examined. 



• To Read the Barometer 



If the observer stands facing the barometer the " short 

 pointer" (black) moves toward the right as the pressure 

 of the atmosphere (or weight of the air) increases, and to 

 the left as the pressure of the atmosphere (or weight of 

 the air) diminishes. The "long pointer" (brass) should 

 be moved by the turning screw so as to coincide with, or 

 exactly cover, the "short pointer" (black). The baro- 

 meter is now set for reading, and the "barometer reading" 

 is found by reading from the left to right on the " main 

 barometer scale" from the lowest figures (or readings) 

 on that scale to that exact division or mark upon that 

 scale to which the " long pointer" points or which it 

 covers. The inches and hundredths of inches are 

 marked on the scale. The inches and hundredths are 

 counted from left to right, or in the same direction as 

 the hands of a watch mov^e, and they are counted in the 

 same way as the hours and minutes on a watch-face are 

 counted. The inches and hundredths are written down, 

 if they are to be written, in the same manner as dollars 

 and cents are written, thus : one dollar and seventy-five 

 cents ; that is, one dollar and seventy-five hundredths of 

 a dollar would be written §1.75, or one and seventy-fire 

 hundredths; $29. 35, twenty-nine dollars and thirty-five 

 hundredths. The "long pointer" pointing on the "main 

 barometer scale" to twenty-nine inches and thirty-five 

 hundredths, the barometer-reading would be twenty-nine 

 inches and thirty-five hundredths of an inch, and would be 

 written "29.35 inches," and so for other readings. 



• Circular issued by the Signal Service of the United States Army — com 

 municated by General Myer, Chief Signal Officer. \ 



Rain Winds and Dry Winas 



There are for each place and for each month two kinds 

 of winds; — 



First — Winds which, blowing from certain directions, 

 are at that place and in that month more likely than any 

 other winds to be followed by rain. These are called 

 "rain winds." 



Second — Winds which, blowing from certain directions, 

 are at that place and in that month less likely than other 

 winds to be followed by rain. These are called "dry 

 winds." 



The "rain winds" and the "dry winds" for each 

 district and for each month are stated in the Farmers' 

 Bulleti7i, or can be had by application to this office. 



The wind direction for any day or time must be seen 

 and taken at each place or station by a vane as well 

 located as practicable. 



The "wind disc" (No. 8) consists of a brass circle, on 

 which slide freely two arcs — a red arc, called the "dry- 

 wind arc " (Na 9), and a blue arc, called the " rain-wind 

 arc" (No. 11). In the centre of the disc is a pointer, 

 turning with a turning-screw, and called the "wind-disc 

 pointer" (No. 10). Around the disc are letters to show 

 directions, as N for north, E for east, NE for north- 

 east, &c. 



The wind disc is made ready for use as follows; — If, 

 for instance, the Farmers' Bulletin, or other report, states 

 that, for any district or place, and for any month, " winds 

 blowing from south or east, or from directions between 

 those points, are found to be the winds most likely to be fol- 

 lowed by rain, winds blowing from north or west, or from 

 directions between those points, are found to be the winds 

 least likely to be followed by rain" -or, in other words, 

 " winds blowing from east or south, or from directions 

 between those points, are rain winds. Winds blowing 

 from north or west, or from directions between those 

 points, are dry winds ;" then, if the instrument is to be 

 used in that month and in that district or place, the rain- 

 wind arc No. 1 1 (the blue) is moved on the brass circle 

 until one end of the arc is at the letter E, which stands 

 for "east," and the other is at the letter S, which stands 

 for "south ; " the dry-wind arc No. 9 (the red) is moved 

 on the circle until one end of that arc is at the letter N, 

 which stands for "north," and the other is at the letter 

 W, which stands for "west." The arcs remain as they 

 are thus placed for the whole of the month. 



At the beginning of the next month the rain-wind 

 direction and dry-wind direction must be located for that 

 month, and the arcs must be again moved on the circle in 

 the same manner until the rain-wind arc and the dry-wind 

 arc touch, respectively, with their ends, the letters for the 

 points named for the rain-winds and the dry-winds for 

 that month. The arcs then remain so placed for that 

 month — so for each month of the year. 



Now, when the wind disc is thus ready, and on any day, 

 the weather case is to be used, (i) The direction in 

 which the wind is blowing is seen by a vane. It is 

 noticed from what direction the wind is blowing, as from 

 the north, south, east, &c. (2) The wind disc pointer 

 (No. 10) is moved by .the turning-screw to point to the 

 compass-letters on the disc^ or between them, showing as 

 nearly as practicable by those letters the same direction, 

 i.e., that from which the wind is blowing when observed. 

 If this pointer, so set, points at either of the ends of either 

 arc, or any part of either arc, it shows, if it so points at 

 the red arc, that the wind is at that time in the dry-v'ind 

 direction, or is a dry wind ; if it so points at the dlue arc 

 that the wind is at that time in the ,rain-v,ind direction, 

 or is a rain wind. 



The hour is noted by a clock or watch, and the time at 

 which a rain wind or a dry wind commenced to blow, or 

 was first noticed, is written down. 



It must be also noticed if the wind shifts, as from blowing 

 from a rain direction to blowing from a dry direction, or 



