ON NINE BALLOON ASCENTS IN 1863 AND 186i, 199 



which it did not rise so rapidly. At 4'' SS"", at the height of 11,000 feet, it was 

 over Lewisham ; at 4'' 42"" neariy stationary ; over Charlton at 4'' 46", and 

 Woolwich at 4'^ SO-" when at the height of 13,500 feet. It then began to 

 descend ; was over Erith at 5'' 9"", moving quickly, crossed over the river 

 at 5" IS"", and reached the ground at 6" 32"" at Wybridge, near Kainham, in 

 Essex. 



§ 3. Description of the Table of Observations. 



All the meteorological observations taken during the ascents axe contained 

 in Table I. 



Column 1 contains the times at which the observations were made. Column 

 2 contains observations of the siphon barometer corrected for temperature and 

 index error. Column 3 contains the readings of the thermometer attached 

 to the barometer. Column 4 contains the readings of an aneroid barometer. 

 Column 5 contains the height above the level of the sea, as reduced from the 

 barometric readings in column 2 on the days the siphon barometer was used, 

 and from column 4 on other days, by the formula of Baily, checked at inter- 

 vals by that of Laplace, which is as follows : — 



Z=logf^) X 60159(1 + it^^^Vl + 0-002837 cos 2 lVi + ^+^??^V 

 \h'J \ 900 A A 20886900/' 



where Z is the height required, and h, h', t and t' the height of the barometer 

 corrected for temperature, and the temperature of the air at the lower and 

 upper stations respectively, L the latitude. The temperature of the air for the 

 position of the balloon has been derived from the readings in column 10, 

 when such have been taken, otherwise from column 6. Columns 6 to 9 

 contain the observations with the dry- and wet-bulb thermometers free, 

 and the deduced dew-point. Column 10 contains the readmgs of a 

 gridiron thermometer. Columns 11 to 14 contain the observations with 

 the diy- and wet-bidb thermometers aspii-ated, and the deduced dew- 

 point. Columns 15 and 16 contain the direct dew-point observations mth 

 DanieU's and Regnault's hygrometers. When mmabers are entered in 

 columns 15 and 16 with " no dew" affixed to them, it is meant that the 

 temperature of the hygrometer has been lowered to the degree stated, but that 

 no dew has been deposited. Column 17 contains the readings of a very deli- 

 cate blackened bulb thermometer fully exposed to the sun's rays. 



The Astronomer Eoyal had observations made every 10 minutes at the 

 Eoyal Obsei-vatorj^, Greenwich, on five days of ascents ; Lord Wrottesley had 

 observations made by Mr. Hough at Wrottesley Observatory on the ascent 

 from Wolverhampton ; E. J. Lowe, Esq., had observations made at Beeston 

 Observatory for the ascents at Wolverhampton and Derby ; and observations 

 were made at my house at Blackheath by Messrs. Yair and Howe on June 27 

 and August 29. 



In calculating the height of the balloon, the observations made at the Philo- 

 sophical Society's Rooms, Ifewcastle, have been employed for August 31 • 

 those at Wrottesley for September 29 ; those at the Eoyal Observatory for 

 October 9, 1863, January 12, April 6, June 13, and June 27, 1864 j those 

 at Nottingham for June 20 ; and those at Blackheath for August 29, 1864. 



The height of Greenwich above the mean sea-level= 159 -feet. 



The height of Wrottesley above the mean sea-level=531 feet. 



The height of Newcastle above the mean sea-level=121 feet. 



The height of Nottingham above the mean sea-level =174 feet. 



The height of Blackheath above the mean sca-level=160 feet. 



