228 USE OF KITES IK METEOROLOGICAL OBSERVATIONS. 



strain upon the wire ])elow it, latterly the lower portion of the main 

 line has been eoniposed of wire 0.038 ineh in diameter that possesses 

 a tensile strength of 8U0 pounds. The Kiehard meteorograph, con- 

 tained in an aluminum cage of about a foot cube, weighs less than 3 

 pounds, and it is onl}" necessary to screen the thermometer from the 

 sun's raA\s to obtain the true temperature of the air, since the wind 

 insures a circulation of air around the thermometer. Another meteor- 

 ograph constructed by Mr. Fergusson records the velocity of the wind 

 on the same drum with the three other elements, and weighs no more 

 than the French instrument. It is shown in tig. 4 (PI. II), and tig. 5 

 (PI. Ill) is a facsimile record, two-thirds actual size. 



The reeling apparatus is an example of how the same apparatus may 

 serve diametrically opposite purposes. In sounding the depths of the 

 ocean the wire must be pulled upward, whereas in sounding the heights 

 of the atmosphere the wire must be pidled in the reverse direction. 

 Therefore the deep-sea sounding apparatus has been altered by Mr. 

 Fergusson to pull obliquely' downward, the wdre passing over a swivel- 

 ing pulley, which follows its direction and registers on a dial the exact 

 length unreeled. Next the wire bears against a pulley carried by a 

 strong spiral spring, b}^ which the pull upon it at all times is recorded 

 on a paper-covered drum turned by clockwork, then it passes several 

 times around a strain pulley, and iinally is coiled under slight tension 

 upon a large storage drum. When the kites are to be pulled down, 

 the strain pulley is connected with a 2-horsepower steam engine, and 

 the wire is drawn in at a speed of from 3 to 6 miles an hour, but 

 when the kites are rising the belt is removed and the pull of the kites 

 unreels the wire. 



The method of making a kite flight for meteorological purposes at 

 Blue Hill is as follows: A kite, fastened to a ring at the end of the 

 main wire, and the me^^eorograph clamped to the wire being in the air, 

 another kite is attached by a cord and the clamp described. The kites 

 are then allowed to rise and to unreel the wire until its angle above 

 the horizon becomes low, when other kites are added, the number 

 depending on the size of the kites and the strength of the wind. After 

 a pause at the highest attainable altitude, the reel is connected with 

 the steam engine and the kites are drawn down. The pauses at the 

 highest point, and when kites are attached or detached, are necessary 

 to allow the recording instruments to acquire the conditions of the 

 surrounding air, and because at these times the meteorograph is nearly 

 stationary, measurements of its angular elevations are made with a sur- 

 veyor's transit, while observations of azinuith give the direction of the 

 wind at the diflerent heights. The time of making each angular meas- 

 urement is noted, so that the corresponding point on the trace of the 

 meteorograph may be found. From the length of wire and its angular 

 elevation the height of the meteorograph can he calculated, it having 



