Morning journal and courier., 1884-05-13
PrOphesyInE Weather.


 The United States signal service, which has accomplished SO much, was organized by General Myer, man whose sobriquet, "Old Probs," is as familiar as household words in every American home. The service was es- tabIished in 1870, and to-day it is the most efficient organization of the kind ever known. It is bureau of the war department, and is composed of 8 force of 800 men. Although essentially 8 military organization. the duties of it's members are not strictly of a mili- tary character. All the grades of rank that obtain in the army obtain in the signal ser vice.
 The object of the signal service is to warn the people of the coming changes of temper ature and approaching storms. and all that these meteorological variations and convul- sions portend. The predictions which as- tonish the world by their accuracy are made from 8 comparison at Washington of local records sent in from stations scattered all over the country. In.this way at Washing ton the authorities have practically birds eye view of the meteorological conditions prevailing all over the continent. The data upon which they make their predictions are the pressure of the air measured by the ba- rometer, the temperature of the air as meas ured by the hygrometer, the velocity of the air as measured by the anemometer, and the direction of the wind as measured by the or dinary wind vane. In addition to these re- cording instruments there are the rain and snow guage and spectroscope. The condi- tiens recorded by these instruments, togeth- CT with the appearance of the clouds, are the means by which the weather likely to pre- vail in any locality is determined.
 Among the recording instrumsnts the uses of the thermometer and barometer are gener- and VpiE fhaip aid may n a certain extent, is his own weather prophet. The hygrometer consists of pair of ther- mometers. The bulb of one is enveloped in piece of muslin that connects with vessel containing cold water. The muslin covering g the bulb is thus kept damp, and as 8 given amount of heat is required to produce given amount of evaporation, the thermometer having it's bulb covered with damp muslin will record lower temperature than the thermometer having it's bulb intact. The differ ence between the two thermometers indicates the amount of moisture there is in the air. If one of the thermometers records 45 de- grees and the other 50 degrees. it demon strates that the atmosphere is very dry, and that it retains but 25 per cent. of the moist ure 1t is capable of holding.
 The anemometer is an instrument with four hemispherical cups at the extreme ends of two rods which cross each other at right angles. This contrivance is placed on the top OL SplnOAo AG bA0 DhS0 OI VI ulCA aE0 cog-wheelS. The, cups turned by the wind, impart their motion through the spindle by means of an endless screw to a series of cog wheels the revolution of which are taken as the measure of the winds force. Five hun- dred revolutions of the cups equal one mile. There is an ingeniously contrived electrical apparatus connected with this, by means of which 8 complete record of the wind varia tions is transferred to paper. For every mile of the winds velocity an electric circuit is completed and the fact is immediately me- chanically telegraphed to the officer below.
 The spectroscope has proved 8 useful ad- junct to the other instruments It is used particularly in the prediction of local rain storms especially those of the summer months. When the spectrum shows 8 strong rain band in the upper atmosphere. and the hygrometer demonstrated that the lover at- mosphere is saturated with moisture, there is strong probability of rain. The advan- tage of the spectroscope as meteorological instrument lies in the fact that it affords a means of examining the condition of the upper atmosphere, which is altogether out of the range of the other instruments.
 The rain gauge is simple instrument of funnel shape. The superficial area of the bell shaped top is ten times greater than that of the receiving pipe, so that the depth of water in the receiver is actually ten times greater that the rainfall on the level. The smallest rainfall in this way can be accurately computed. A rainfall of HOO part of an inch could De measured. fall of snow is measured by the game instrument. After g snow storm is over, or during long snow storm, the gauge is taken into 8 warm room and the snow allowed to melt From 10 to 12 inches of snow are equal to an inch of rain.