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variation, but during which time there was a great increase of temperature, and consequently the relative humidity decreased with rapidity from 95 to 39. The balloon then fell from 19,500 feet to 19,200 feet, the temperature of the air decreased to 38°, and the dew-point increased from 1910 to 21°, and the humidity increased to 49. After 19,200 feet the dew-point decreased with rapidity to 16° at 20,000 feet, with a humidity of 48; and afterwards with great rapidity to a dew-point of less than -12° at 21,000 feet; and at heights exceeding this the dew-point is unknown, but was certainly lower than -20°, and probably as low as -30° up to 24,000 feet; from the observations of the dry- and wet-bulb thermometers it seems to have been as low as -50° at 25,000 feet; therefore the tension of vapour above 20,000 feet must have varied from about 0·015 in. to less than 0.01 in., and the degree of humidity to have decreased to 2, or even less. In this series we can distinctly trace a stratum of moist air in the cloud above 4000 feet, and again between the heights of 9500 feet and 11,500 feet. From 11,500 feet to 19,000 feet the tension of vapour differed but very little from 0-13 inch; then the amount of water present in the same mass of air was nearly constant for 8000 feet in vertical height; immediately after this there were some irregularities, and above 20,000 feet the air was dry, being almost free from vapour.

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July 30.-The temperature of the dew-point in this ascent was constantly varying on the ground it was 53°, at 1000 feet it was 444°, but at intermediate points it was sometimes on one side and sometimes on the other, to the amount of 1° or 2° from the curve-line joining these points; then up to 2400 feet there was a stratum of moist air, and above 3600 feet there were strata of moist and dry air alternately for 2000 feet; higher than this there was a stratum of dry air from 5600 to 6400 feet, and higher still one of moist from 6500 feet to the highest point reached: these terms, moist and dry, have reference to a curve-line, which was made to pass near every point as laid down from observation; and the same phenomena generally prevailed during the descent. The relative humidity generally increased to the highest point reached.

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August 18.-The temperature of the dew-point decreased from 57° on the ground to 52° at 1000 feet, increased from 5210 at 1000 feet to 5310 at 1700 feet whilst passing through mist, decreased to 50° at 2000 feet, and varied but little till 3800 feet was passed; the degree of humidity varying from 62 on the ground to 96 at 3800 feet when in a cumulus cloud. The dewpoint decreased rather quickly to 41° at 5000 feet, and with less rapidity to 26° at 11,000 feet, the humidity varying from 96 at 3800 feet to 59 at 11,000 feet. Whilst almost stationary in elevation for some time, at the highest point the temperature of the air increased, whilst that of the dewpoint decreased, so that the degree of humidity changed from 59 to 51. The balloon then descended: the temperature of the dew-point increased gradually to 31° at 8200 feet, and to 38° at 7800 feet: the humidity was 61 at the lower elevation: the dew-point remained nearly at the temperature of 37° from 7800 feet to 6000 feet, and rose to 48° at 3500 feet-its lowest 1862.

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point; the humidity increased from 53 at 7000 feet to 77 at 3500 feet. The balloon then ascended, and the dew-point fell to 37° at 8000 feet, and the humidity from 76 to 61.

The dew-point then increased somewhat to 394° at 8500 feet, with a humidity of 65: from this elevation the dew-point decreased to 21° at 11,600 feet, with a degree of humidity of 51. The dew-point then turned to increase, and was 25° at 12,400 feet, giving a humidity of 57 at this elevation; it then decreased gradually to 23° at 14,500 feet, and then rapidly to -840 at 20,100 feet: the relative humidity was 59 at 12,400 feet, and 22 at 20,100 feet. Above 20,000 feet a dry stratum of air was entered and no dew was deposited on either of the hygrometers, their bulbs being reduced to a temperature of -10°.

In descending, the dew-point increased steadily to 14° at 12,000 feet. remained at this reading till nearly 10,000 feet, then increased rapidly to 34° at 8000 feet, and then gradually and almost uniformly to 57° on the ground: the degree of humidity increased from 31 at 18,000 feet to 36 at 14,000 feet, remained at this value to 12,000 feet, decreased to 28 at 10,000 feet and then increased to 77 at 4000 feet, and was 66 on reaching the ground. In this series a narrow stratum of moist air was passed through between 1000 and 2000 feet from the earth, and then another on passing through a cumulus cloud at the height of 3800 feet; above this to 11,000 feet there was a constant decrease in the amount of water; the balloon then descended and the vapour increased steadily to 8000 feet, then a stratum of moist air was met with from 1000 to 2000 feet in thickness; from 6000 feet to 3500 feet on descending, and again from 3500 to 7000 feet on ascending, there was an increase and decrease respectively; between 8000 and 9000 feet and between 11,000 and 12,000 feet dry strata were passed; then for 2000 feet there was but little variation in the humidity of the air, above 15,000 feet there was a rapid decrease in the amount of vapour, till the air became very dry above 20,000 feet. In the descent one stratum only of moist air was passed through, viz. between 13,000 feet and 9000 feet from the earth.

August 20.-Between 400 and 600 feet a dry stratum of air was passed, then there was but little variation in the temperature of the dew-point, and the air was for the most part humid during the ascent.

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August 21.-The temperature of the dew-point decreased from 60° on the ground to 57° at 400 feet, then increased to 59° from 500 to 700 feet whilst passing through a thick mist, and to 60° at 1000 feet; a decline then took place to 50°.8 at 1300 feet, and 50°.9 at 2000 feet; from 2000 feet to 3200 feet there was at first a gradual, then more rapid decline to 40°-8 at 4000 feet; on entering cloud the dew-point increased to 41°.6, and on leaving it at about 6000 feet there was a sudden fall of 2°. The relative humidity was 94 on the ground: the air was saturated for 200 feet from 500 to 700 feet; the humidity was 74 at 1000 feet, 79 at 1300 feet, and 97 in the cloud. Above the cloud the dew-point decreased quickly and with but slight irregularities till the height of 10,400 feet, where it was 1440, with a humidity of 48; at 14,000 feet the dew-point was -14°, and the air was dry, the relative humidity being 18. Above 14,000 feet the temperature of the dew-point declined to -20°, with a humidity of 12 only. During the half-hour this height was maintained the temperature of the air increased, whilst that of the dew-point diminished, so that the air became drier. On descending the air continued dry, the dew-point increased from -22° at 14,000 feet to +19° at 10,000 feet, the humidity increasing to 51; there was but little variation in the dew-point in the next 2000 feet, but during this space the temperature of the air increased 7°, so that the relative humidity was irregular. At 7500 feet the dew-point was 20°, at 6900 feet it was 42°; on approaching the clouds at the former height the relative humidity was 38, and at the latter it was 88. Whilst passing through the cloud both the temperatures of the air and dew-point declined, the latter to 3810, and the humidity was 89. On descending below the cloud the dew-point increased gradually from 38° at 4000 feet high, then quickly to 45°-7 at 3000 feet, then fell to 44°.7 at 2500 feet, then increased to 56° on reaching the ground. At 5800 feet the relative humidity was 83, between 2500 feet and 1500 feet it was 76 or 77, and it was 71 on the earth.

In this series, till the clouds were passed, there were two or three layers of moist air; but from the time of passing above the clouds, the air was constantly increasing in dryness till the greatest height was attained, and

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increasing in dampness in the descent to 10,000 feet; then a dry stratum of air was met with, till on approaching the clouds and passing through them s moist stratum was passed; below the clouds there were but slight variations till the descent was completed.

September 1.-The changes of the dew-point in this ascent were more frequent and more abrupt than on August 20; there seemed to be different layers of moist air, varying in thickness from 200 to 300 and 400 feet up to 3000 feet, and above this the variations were smaller in amount and less in number. In the descent a moist stratum of air was met with between the heights of 2000 and 1300 feet.

September 5.-The temperature of the dew-point increased from 484° on leaving the earth to 50° at 700 feet; it then began to decrease, and was

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