USE OF KITES IN METEOEOLOGICAL OBSERVATIONS. 229 



been found that the sag- of the wire, or its deviation either in a vertical 

 or a horizontal plane from the straight line joining kite and reel, does 

 not cause an error exceeding 3 per cent in the height so computed. 

 When the meteorograph is hidden b}- clouds, the height above the last 

 point trigonometrically determined is computed from the barometric 

 record by Laplace's formula. At night there is only the barometer 

 from which to determine the height, for, although an attempt was 

 made to use a lantern to sight upon, yet it soon becomes invisible, or, 

 when seen, is confounded with the stars. Before and after the flight 

 the thermometer and hygrometer of the meteorograph are compared 

 with the standard instruments. 



Since the use of wire and more elEcient kites the heights have been 

 greatly increased. Thus the average height above the sea attained 

 by the meteorograph in the thirty-iive flights made during 1898 was 

 more than a mile and a third, whereas the average height of all the 

 ascents prior to 1S!»T was less than half a mile. The extreme height 

 of 15,807 feet, reached in July, 1900, exceeds the altitude of Mont Blanc, 

 and also the greatest height at which meteorological observations have 

 been made with a ))alloon in the United States. The progress upward 

 each year is shown in this table: 



Heights aborc xca Jerri of kite fi<jlits <it Blue lUlL 

 [Blue Hill is 630 feet above the sea.] 



The average of the highest points recorded in each one of the 

 flights during August, 1898, exceeded a mile and a half, and on 

 August 26 the meteorograph was raised 11,140 feet above Blue Hill, 

 or 12,070 feet above the neighboring ocean. The meteorograph was 

 suspended from the topmost kite, one of the Lamson pattern, having 

 71 square feet of lifting surface, and this was increased to a total of 

 119 square feet by four kites of the modified Hargrave type that were 

 attached at intervals to the wire. The 5 miles of wire in the air 

 weighed 75 pounds, and the total weight lifted, including kites and 

 apparatus, was 112 pounds. The meteorograph left the ground at 



