[36] The phenomenon here depicted is closely allied to those tinted halos which are seen in so much diversity and under so many modifications around both sun and moon. In Schumacher’s ‘Astronomische Jahrbücher’ (Altona, 1823) Fraunhofer has detailed the theory of these halos, and has proved his assertions by many examples that had fallen under his own observation. Whenever the sun or the moon is surrounded by a halo, the sky is ordinarily veiled in light vapours. If the phenomenon is perfect, the rings of this halo are seen to be of the colours of the rainbow. Fraunhofer divides these halos into two classes: viz., halos of a small and halos of a large diameter. If the red tint is outside and away from the luminous body, as in the present case, he calls it a halo of the smaller kind; but if the red is inside and next to the luminous body, it is a halo of the larger kind. This latter case is closely allied to the phenomenon of parhelia. The cause of these tinted halos is to be found in a diffraction of light through globules of vapour, and Fraunhofer has given proof that the light, in passing across the edges of these globules, would assume an appearance of diffraction similar to that which would be caused by its passing through minute apertures. For the formation of a tinted circle it is necessary that the globules should be equally diffused and of an equal magnitude. If the globules were very irregular, there would be only a bright glare, because the eye would receive rays of various colours from one and the same spot in the atmosphere; then the result would be that the light would be white, as in the case under our notice it appeared directly round the outline of the cloud, and also beyond the outside ring of red, so that the coloured circle was bounded on each side by a rim of white light. The smaller the globules of vapour, the larger are the tinted rings, for according to the theory the diameters of the rings are in inverse ratio to those of the globules. According to another theory represented by Galle (Poggendorf’s ‘Annalen,’ vol. xlix.), one cause of these tinted halos is the presence in the atmosphere of ice-crystals of microscopic minuteness; but this hypothesis seems confuted by the fact that similar phenomena have frequently been witnessed within the tropics (Alex. von Humboldt, Voyage II., p. 309). This phenomena of the 18th of May, 1869, was remarkable for the form of the tinted circle, which corresponded exactly with the accidental outline of the clouds, which presented a threefold curve, thus
. Thus the entire rim of the cloud became a series of luminous sunlight points formed of globules of vapour, making a halo of the smaller class, and sending forth their own shadows.
[37] Vide Speke’s Journal, p. 462.
CHAPTER IX.
Tour through the Mittoo country. Early morning in the wilderness. Soldier carried away by a lion. Dokkuttoo. Fishing in the Roah. Feeding a slave caravan. Ngahma. Dimindoh, the hunter’s Seriba. Wounds from the grass. Dangadduloo. Entertainment in the Seribas. The river Rohl. Reception at Awoory. Footsore. Trial of patience. People of the district. Poncet’s Seriba Mvolo. Mercantile prospects for the Egyptian Government. Fantastic character of landscape. Structure of pile-work. Rock-rabbits. Rock-rabbits’ feet. Nile cataract in miniature. The Tinnea æthiopica. Seriba Karo on the Wohko. Reggo and its breed of dogs. Kurraggera. Aboo Sammat’s festivities. A speech of the Kenoosian. Aboo Sammat and the subjugated chiefs. Deragoh and its mountains. Kuddoo on the Roah. Fear of lions in the forest of Geegyee. Return to Sabby. The Mittoo people. Inferiority of race. Disfiguration of the lips by Mittoo women. Fetters of fashion. Love of music.
I spent December and January in a tour of considerable extent through the adjacent Mittoo country, being desirous of visiting some Seribas recently established by Aboo Sammat, and by means of which he had extended his frontiers far onwards towards the east. I obtained ten bearers for the transport of my baggage, and a Nubian captain of Aboo Sammat’s company was expressly appointed to act as guide and to provide for my accommodation all along the route. I was accompanied likewise by three of my own Khartoom servants.
A short journey to the north-east brought us to Boiko, where, enclosed by a dense forest, was situated Aboo Sammat’s harem. A lady here, the first wife, a daughter of the Niam-niam chief Wando, although she did not permit herself to be seen, was near at hand to do the honours: she was so far civilized that she entertained me with coffee and several Khartoom dishes.
Proceeding eastwards we reached the little river Tudyee, which, flowing past Sabby at a distance of about two leagues to the east, ultimately joins the Roah (the Nam Dyow of the Dinka); at this time of year it is about twenty feet deep, and murmurs along a channel from twenty to thirty feet wide; now and then it forms deep basins, which never fail to be full of fish. We made our first night-camp near a fine tamarind, which will probably for years to come be a landmark as conspicuous as it was at the time of my visit; it was the usual halting-place of all caravans from east to west, and the traces of previous encampments, dilapidated straw-hats, vestiges of fires and fragments of bones bore ample testimony to the fact.
At this season a slight dew was perceptible towards five o’clock in the morning. The nights were calm and, in comparison with the day, were considerably cooler than in summer, when in the interior of the huts there is hardly any difference in temperature to be distinguished. Throughout the day, however, a strong north wind blew incessantly, which towards the afternoon increased almost to a hurricane. There is a peculiar charm in these early morning hours, and no one can wake from his repose in a night-camp in the wilderness without a sense of calm enjoyment of the delights of nature. As soon as the horizon reddens with the dawn the solitude is enlivened by a chorus of ring-doves, here the most frequent of their kind, and by the cackling of guinea-fowl. The traveller is aroused daily by their serenades, and, without much strain upon his imagination, he could almost persuade himself that he has been long resident in the same spot, so familiar does the cooing of the doves become.