Meteorological Observations. 335 



in all direclions, witliout a wiiid, the whole heaven will bcconia 

 overcast in a remarkably short time. The same thini? will 

 sometimes occur iiearly 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 jm- 

 mefliately on the land and sea. The height and thickness of 

 these strata, their connexion with cross or opposite currents of 

 wind in the regions where they subsist, and the laws of their 

 formation and gradual inter-mixture, deserve to be studied with 

 care, and with reference to the hygromctic state of the air at 

 the time and place, and for several hours before and after. 



Of Thunder and Lightmng, and of the Electrical state 



of the Air. 



Connected with this part of the subject is the (»bservation of 

 shooting Stars and luminous Meteors. Remarkable ones should 

 be noticed, and the moment of their appearance, their direction, 

 duration, length of path, and cnu-se among the S'as, ascer- 

 tained and noted, with the phseromena of their increase and 

 decay of liglit, apparent size, separation into parts, trains left 

 behind, &c. The ^enerf./ direction (if any) wliich they observe 

 on particularnights, is a point also to he attended to. Such 

 are the frequency ai:d brilliancy of these splendid phsenomena 

 in the clear sky of this Colony, that there can be no doubt of 

 their affording an available method of ascertaining the differ- 

 ences of longitude of the most distant stations, if duly observed 

 by persons furnished with means of ascertaining the time. 



Thunder storms of course will he noticed when they occur 

 under the general head of the weather, but it is of consequence 

 also to notice distant lightning, not accompanied with thunder 

 Hudiblc at the place of observation (by reason of its great 

 distance),* especially if it takes place many days in succession, 

 and to note the quarter of the horizon where it appears, and 

 the extent 't embraces. In an actual thunderstorm, especial 

 notice should be taken of the quantity of rniii that fii\b, and of 

 the fits or intermittances of its fall, as corresponding, or not, 

 to great bursts of lightning, as also of the direction of (he 

 wind and the apparent progress of the storm with or aj^ainst it. 



Observations of the Electrical state of the Air in serene 

 weather are unfortunately too much neglected. The apparatus 



* Thunder can scarcely ever be heard more than 20 nr 30 miles from 

 the flash which products it. Lightning on the oiher hand may be sceo 

 (or at least its rfflexion on the I loads, forming w hat is rallrd xktet lif^ht- 

 ninfr) at the distance of ISO or 200 miles. 



