ELECTRICAL DEVICE FOR OPERATING ANEMOMETER STOP-WATCH.
Fig. 78.
A. 6-1/5 seconds, about; 1° 1' minus (depression); 4° 18' plus (elevation).
The Atmosphere-board.
Q. Describe the atmosphere-board.
A. This is merely a graphic table by means of which the reference-numbers to be recorded on the atmosphere-aeroscope indicator can be determined from the readings of the barometer and thermometer. The arguments are barometer and thermometer readings, and the reference-numbers are indicated by diagonal lines. The thermometer axis is horizontal and the barometer axis is vertical. To increase the ease and rapidity of reading the barometer scale is graduated on a movable T square.
The method of construction is shown in Fig. 79.
Operation.—Set the T square for the thermometer reading and note the diagonal line which intersects the fiducial edge of the T square the nearest to the barometer reading. The atmosphere dial is graduated to ½ per cent. The reading of the board should be taken to the nearest half reference-number.