Meteorological Observations. 147 



Of the State of lhe\Sky — In describing the state of the sky as to clouds, Ac. 

 the observer will bear in mind that it is only in that region of the sky which 

 is vertically above him that the true forms and outlines of the clouds are 

 exhibited, and the area they cover, as well as the intervals between them dis- 

 tinctly seen. As they approach the horizon in any direction, their extent is 

 foreshortened by perspective, their apparent magnitude diminished by dis- 

 tance, and their intervals covered in and hidden by their mutual interposition. 

 In estimating therefore the quantity of clouds in the sky, regard must be had 

 to this, and our judgment should rather be formed on a view of the region 

 extending from the zenith every way half way down to the horizon, that 

 from the aspect of the heavens below that limit. It would be better to no- 

 tice both, and state, separately, the proportions in which each are covered, 

 and the quarter of the horizon towards which the chief masses in the lower 

 region lie. 



The general aspect of Clouds, as classed under the heads Cumulus, Cirrus, 

 Stratus, &c. should be noticed, and especially the height of this inferior sur- 

 face, or the level of the vapm$r plane, should be estimated. In a mountain- 

 ous region this is easy, so long as the vapour plane is below or not far above 

 the summits of the hills, and in such regions the formation and dissipation 

 of cloud in the nei^rhbourhood of the mountain summits, under the influence 

 of certain winds, form a subject of study of a highly curious and interesting 

 nature. 



The formation of Clouds at night, during calm weather, under the influence 

 of a gradually descending temperature, is another point worthy of attention. 

 It frequently happens, that, without any perceptible wind, the sky will sud- 

 denly become hazy in some one point, and the haze condensing and spreading, 

 in all directions, without a wind, the whole heaven will become overcast in 

 a remarkabl}-^ short time. The same thing will sometimes occur nearly at 

 the same hour for many nights in succession. Such phenomena should be 

 noted whenever they occur. 



Two or even three strata of clouds are very common in this district of 

 South Africa. The lowest frequently resting immediately on the land and 

 sea. The height and thickness of these strata, their connexion with cross or 

 opposite currents of wind in the regions wliere they subsist, and the laws of 

 their formation in gradual intermixture, deserve to be studied with care, aod 

 with reference to the hygrometic state of the air at the time and place, and 

 for several hours before and after. 



Of Thunder and Lightmng, and qf the Electrical state of the Air. — Connected 

 with this part of the subject is the observation of shooting Stars and lumi- 

 nous Meteors. Remarkable ones should be noticed, and the moment of their 

 appearance, their direction, duration, length of path, and course among the 

 Stars, ascertained and noted, with the phenomena of their increase and decay 

 of light, apparent size, separation into parts, trains left behind, &c. The^ 

 neral direction (if any) which they observe on particular nights, is a point also 

 to be attended to. Such are the frequency and brilliancy of these splendid 

 phenomena in the clear sky of this colony, that there can be no doubt of their 

 affording an available method of ascertaining the differences of longitude of 



k2 



