[23]

P. Louise Jan. 14 (1)

— May 6 to 8th

[With respect to the time of year, the falls have always occurred in the months of January, February, March and April; but in the case of the Princess Louise in 1840, as late as on the 9th of May.]

Tuckey April 5th (2)

"In Tuckey's Narrative of the Congo Expedition (p. 10),10 a discoloured sea and a hazy atmosphere are described on the 9th of April in lat. 22° N. and long. 19° 9' W., when 32 leagues from the main-land."

James March 7. to 10 (3)

"Robert Bastard James, Lieutenant and commander of the brig Spey from 1835."

Burnett February 12 to 15' 4

"Nautical Magazine, 1837, p. 291.5 Mr. Burnett, on February 12th to 15th, in sailing from (lat. 4° 20' N., long. 23° 20' W.) to (lat. 8° N., long. 27° 20' W.), a distance of 300 miles, with the wind N.E., preceded by a S.E. squall which veered to E.S.E. and then to N.E., had the sails, rigging and mast covered with red dust. The dust began to fall as soon as the wind became N.E.: the atmosphere was very hazy. The nearest land was 600 miles distant. The same phænomenon was observed by Mr. Burnett in April 1836."

Alexander March 29th 5

Clarke Feb. 2 & 4 6

"The dust described by the Rev. W. Clarke fell February 2nd to the 4th, 1839, when between (lat. 21° 14' N., long. 25° 6' W.), and nearly (lat. 12° 36' N., long. 24° 13' W.)."

C. Darwin Jan 16' 7

Arlett 8

"Lieut. Arlett found the water so discoloured (8), that the track left by his ship was visible for a long time; and he attributes this in part to the fine sand blown from the deserts, 'with which everything on board soon becomes perfectly caked.'"

Roussin 9

"I may add, that Baron Roussin (5), during his survey of the north-western African coast, found, that whilst the wind keeps parallel to the shore, the haze and dust extend seaward only a short distance; but when during the above four specified months the harmattan2 blows from the N.E. and E.N.E., accompanied by tornados, the dust is blown far out, and is raised on high, so that stars and all other objects within 30° of the horizon are hidden."

Horsburgh 10

[23v]

[calculations not transcribed]