October 14, igogl 



NA TURE 



467 



where the vegetation proved to be richer than any 

 hitherto met with. It was said that the rains which had 

 fallen a few months earlier were more copious than any 

 experienced during the previous fifteen or twenty years. 

 It was no doubt a consequence of this that the annual 

 constituents of the flora were unexpectedly abundant. 

 Warmbad is noted for a number of warm springs (35° C.) 

 the waters of which — like so many of the natural waters 

 of the south-west coast — are impregnated with sulphuretted 

 hydrogen. The railway between Keetmanshoep (3300 feet) 

 and the sea ascends to nearly 5000 feet at !.'\us, where 

 the vegetation presents many karoid features. From !Aus 

 the descent — at first gradual, later more rapid — is un- 

 interrupted. About 30 km. west of !Aus (no km. from 

 the coast) the desert commences very abruptly at 2700 



'PEI^a SLABEN 



nenwTfial CT^tdutlirH/, 



Soutk ■ Ms-t Africa,, KjOl-(j 

 oteZum, I 



lynjJifaJrjmju/tnafS,] -— 



/Tow 6*/Ta/y J 



feet. In this latitude there appear to be few forms 

 peculiar to the desert itself and its flora consists 

 very largely of the more resistant of the species found 

 at higher levels and under less arid conditions. Never- 

 theless, the eastern boundary of the desert is remarkably 

 sharp, and approximately coincides with the western limit 

 of precipitation from clouds condensed upon the neighbour- 

 ing highlands. Within 50 km. of the sea the sharp, bare 

 mountain peaks and ridges are frequently more or less 

 buried in sand-dunes, the materials of which are blown 

 up from the lower-lying fiats, leaving behind the worn 

 gravels from which diamonds are now being obtained over 

 an extensive area. Nearer the coast the scenery is re- 

 markably gaunt and rugged and the wind-swept surface 

 is frequently quite bare of vegetation. 



NO. 2085, VOL. 81] 



Leaving Liideritzbucht by sea on February 26, I arrived 

 in Swakopmund eighteen hours later, and on March 2 

 reached Welwitsch (lat. 22°), a Welwitschia locality 

 previously visited in 1907 in company with iVIr. E. E. 

 Galpin.' The object of this visit was to obtain later stages 

 of the Welwitschia embryo than were present in material 

 collected in 1907. The flora in general was this year very 

 much poorer than two years earlier. Not only were many 

 of the smaller plants then collected not found at all, 

 but woody species formerly obtained in flower or fruit 

 now showed no signs of reproductive activity ; this also 

 applies to some extent to Welwitschia itself, for only a 

 small proportion of the plants had coned. The explana- 

 tion of this very striking difference seems to be contained 

 in the meteorological records. Between^ November i, 

 igo6, and January 31, 1907, 12-8 mm. of rain were 

 measured at Welwitsch; in the corresponding period of 

 igo8-9 the rainfall was 5-9 mm. In December, 1906, the 

 fall was 12-5 mm., an amount very much in excess of 

 that recorded for the whole of each of the years 1907 and 

 igo8. We have here, then, another example of the re- 

 markable influence of a small additional rainfall upon both 

 the annual and perennial constituents of a desert flora. 



A large number of the Welwitschia plants present in 

 1907 in this easily accessible locality have been removed 

 in the interval, and, at the same rate, a few years would 

 probably have seen the complete disappearance of all plants 

 from the vicinity of the railway, for there is here no sign 

 of seed-reproduction. It is therefore very satisfactory to 

 note that His E.xcellency the Acting Governor has issued 

 instructions for the protection of the plants that remain. 



H. H. W. Pearson. 



RESEARCHES ON THE ACTION CENTRES 

 OF THE ATMOSPHERE.^ 



TN the domain of world meteorology, that is, the com- 

 ■*■ parison and discussion of meteorological data of widely 

 distributed stations over the earth's surface. Prof. H. 

 Hildebrand Hildebrandsson has, during the last decade or 

 so, been making some very important communications. 

 He has clearly emphasised the fact that the laws which 

 rule the general movements of our atmosphere will never 

 be found if observations are only made in civilised 

 countries on the earth's surface. Our atmosphere is a 

 mass of air resting both on the continents and the oceans, 

 and modern researches have shown that a large perturba- 

 tion at one time in one area may be intimately associated 

 with a perturbation of an opposite nature in the antipodal 

 part of the world. Although several workers many years 

 ago intimated the positions of isolated areas which 

 behaved in a reverse or see-saw manner meteorologically, 

 it was Prof. Hildebrandsson who first directed attention to 

 a great number of such areas. In more recent times these 

 isolated instances of barometric see-saws have been found 

 to be part of really one general law applying to the move- 

 ments of our atmosphere. This general law has yet to be 

 more minutely investigated, for it is, as Prof. Hildebrands- 

 son states, " une verity avec des grandes modifications." 

 There is little doubt, nevertheless, that world meteorology 

 has made a considerable advance since the discovery of 

 these simultaneous reverse-pressure changes, and one is 

 now in a much better position to state where on the 

 earth's surface observations should be made. 



Every attempt should therefore be made to utilise islands 

 in the large oceans, even if the sole occupants of the 

 islands are the meteorological observers themselves, for 

 until the air movements over the oceans are carefully 

 observed and recorded we shall still be left to a great 

 extent in the dark. 



Prof. Hildebrandsson 's most recent memoir deals chiefly 

 with the northern latitudes of the northern hemisphere, 

 and is devoted to a discussion of data with respect to the 

 simultaneous compensation between types of seasons in 

 different regions. The meteorological data here dealt with 

 relate mainly to certain regions between the east coast of 



1 Nature, vol. Ixxv. , p. 536. 



- Meteorological observations at this station were commenced in November, 

 1906. 



3 Kungl. Svenska Vetenskapsakademiens Handlingar, Band 45, No. 2. 

 III. '' Sur la Compensation entre les Types des Saisons simultantfs en djf- 

 fcrentes Regions de la Terre." By H. Hildebrand Hildebrandsson. 



