TRANSACTIONS OF THE SECTIONS. 17 
By the foregoing table it appears that Jersey and Torquay have the most mode- 
rate temperature, the extremes being only 29° and 24°, whereas at Hastings and 
London they are 37° and 49° —not rising above 78° and 75° at the former, and as 
high as 84° and 86° at the latter, whereas at the latter two, the thermometer fell 
to 47° and 37°: at the former only to 49° and 51°. 
The highest temperature was reached at Jersey on the 6th, at Torquay on the 
15th, at Hastings on the 17th, and in London on the 6th. The lowest, at Jersey, 
Torquay and London on the Ist, and at Hastings on the 15th. The barometrical 
pressure was very uneven in Jersey: the mercurial elevation varied from 30°475 to 
29°386, its greatest elevation being on the 13th; its greatest depression on the 24th. 
At Torquay, the greatest elevation was on the 12th, 30°404; the greatest depres- 
sion on the 20th, 29°343. At Hastings, the elevation was 30°404 on the 13th, the 
depression, 29°365 on the 20th. In London, the greatest elevation was on the 
12th, 30°448 ; the greatest depression, 29°299, on the 20th. The mean pressures 
were—Jersey, 29°630; Torquay, 29°943 ; Hastings, 29°806, and London, 29°860: 
showing that the unsettled state of the weather was caused by effects not indicated 
by the barometer. 
_ Extracts from a Letter to Professor WHEATSTONE from J.D. Hooker, M.D. 
Dearee, West Bank of Soane River, 
Main road to Benares, Feb. 15, 1848. 
“ During our three days’ stay at Cairo I made a few observations on the effects of 
the sun’s rays on the soil, of the depth to which the heat penetrated, as also of the 
power of nocturnal radiation and thickness of soil through which the heat is ra- 
diated. In all these observations I find the great difficulty to be in selecting a 
position where the instrument shall itself be screened from radiation. Limestone, 
sand and sandstone rock, in the desert, have all different temperatures, and, except 
a brisk wind be stirring, give very different results. At the great Pyramid I selected 
two stations, each I thought unexceptionable ; one at the N. face of the N.E. angle, 
the other at the W. face of the N.W. angle, and was mortified to find as much as 
54° difference in the temperature, and several in the dew-point, &c. At each 
angle I shifted the instruments from one to the other face, with the same results. 
At the summit there was considerably more vapour in the atmosphere than at the 
base. The temperature of the two chambers agreed (78°). On the Desert, mid- 
way between Cairo and Suez, I found a little before sunrise, after a very cold night, 
the dewy surface to be cooled down to 44° (if in shade 47°), and the increase of 
temperature to be 1° an inch down to 10 inches; similar soil on the previous and 
succeeding day was heated (at 3 p.m.) to about 80°, and the power of the sun’s rays 
penetrated to more than that distance. 
“« At Suez we embarked on board the Hon. Company’s steam-frigate ‘ Moozuffer ’ 
for Calcutta, and I observed three times a day the temperatures, dew-point, &c., but 
not the barometer, for my ‘Newman’s Portable’ pumped so much as to render it 
impossible to observe within two-tenths of an inch; this was owing to the great 
power of the engines. Some of the phenomena are very curious. In the first 
place, the waters of this Gulf are salter than those of any other sea having a free 
communication with the greater oceans, and contains three-tenths more salt in an 
equal bulk than the Indian Ocean does. This high specific gravity decreases on 
the passage down to Mocha, where the increase is diminished to two-tenths, and 
suddenly to the usual standard of sea-water. My attention was first drawn to this 
by the chief engineer, with whom I conducted such experiments as the motion of 
the vessel allowed. During Ross’s voyage I frequently examined the water (with 
Capt. R.), and whether from the various oceans we passed through, or different 
depths (down to 800 fathoms) in those oceans, always obtained a very constant 
quantity of salts. I also inquired about the waters of the Persian Gulf, and am 
assured that they do not differ from that of the Indian Ocean. From the Straits of 
Bab-el Mandeb to Cape Comorin I perceived no difference. There are further three 
classes of winds in the Red Sea, very remarkable in their distribution. During all 
June, July, August and September a north wind prevails throughout the sea, pro- 
ey I suppose by the heated continents of Arabia, and especially Africa; and the 
848, Cc. 
