soon became invisible, or, when seen, was confounded with the stars. Before and after the flight the meteorograph is hung upon a tripod in the free air, in order that its thermometer and hygrometer may be compared with the standards. HEIGHTS ABOVE SEA-LEVEL OF KITE-FLIGHTS. (_Blue Hill is 630 feet above the sea_) ----+----+----------------++------------------------------------------- | No.|Heights in Feet || Percentages of Records above Year| of +-------+--------++-------+--------+--------+--------+-------- |Rec-|Mean of|Absolute|| 500 m.| 1000 m.| 1500 m.| 2000 m.| 3000 m. |ords|Maximum|Maximum || (1640 | (3280 | (4920 | (6560 | (9840 | | | || ft.) | ft.) | ft.) | ft.) | ft.) ----+----+-------+--------++-------+--------+--------+--------+-------- 1894| 2 | 1,860 | 2,070 || 50 | 0 | 0 | 0 | 0 1895| 28 | 1,673 | 2,490 || 59 | 0 | 0 | 0 | 0 1896| 86 | 2,772 | 9,327 || 78 | 28 | 9 | 4 | 0 1897| 38 | 4,557 | 11,716 || 95 | 68 | 45 | 21 | 5 1898| 35 | 7,350 | 12,070 || 100 | 92 | 80 | 66 | 20 ----+----+-------+--------++-------+--------+--------+--------+-------- Since the use of wire and more efficient kites, the heights have been greatly increased. Thus the average height above the hill attained by the meteorograph in thirty-five flights made during 1898 was more than a mile and a quarter, whereas the average height of all the ascents prior to 1897 was about a quarter of a mile (see Table). The average height of the meteorograph above the hill, in all the flights during August 1898, was nearly a mile and a half, and on August 26 the meteorograph was raised 360 feet higher than ever before, its altitude, determined trigonometrically, being 11,440 feet above Blue Hill, or 12,070 feet above the neighbouring 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 149 square feet by four kites of the modified Hargrave type, that were attached at intervals to the wire. The five miles of wire in the air weighed 75 lbs., and the total weight including kites and apparatus was 112 lbs. The meteorograph left the ground at 10:40 a.m., attained its greatest height at 4:15 p.m., and returned to the ground at 8:40 p.m., a feat which it would be difficult for a man to equal on a mountain. The cumulus clouds were traversed three-quarters of a mile from the earth, and above them the air was found to be very dry. On the hill the air temperature was 72∞, when it was 38∞ in the free air 11,440 feet above, and the wind velocity increased from twenty-two to forty miles an hour. These figures give an idea of the change of atmospheric conditions which occurs, but the conclusions deduced from the Blue Hill kite-flights will be discussed in the next chapter.