500 



NA TURE 



[October 21, 1909 



■slopes of the Chella Range. The railhead is situated in 

 an open forest of stunted trees, among which Acacias, 

 a Bauhinia and the Baobab are prominent, with wide, 

 ;grass-covered glades. This formation extends to the lower 

 slopes of the Chella Range becoming denser as it ascends 

 until, near the summit, it effects a junction with a 

 Savannah, the characteristic species of which include a 

 number of Proteacese and other southern forms. The 

 western face of the Chella Range rises sheer to some 

 3000 feet from the forest which clothes its base, above 

 which the bedding planes of its grey, lichen-covered sand- 

 stone are plainly visible. Except for its great extent, the 

 whole range bears a striking resemblance to Table Moun- 

 tain as seen from Table Bay. Opposite Capangombe there 

 is a gap, the entrance to a kloof up which winds a steep 

 footpath to the top through an increasingly dense, dripping 

 forest, with a magnificent undergrowth of maiden-hair and 

 ■other ferns. Xear the summit a tall Euphorbia with the 

 tiabit of E. graitdidens occurs in great abundance. 



Leaving the Boer village of Humpata (6000 feet) on 

 May 10, we approached the Cunene along the now well- 

 ■known track down the valley of the Caculovar. On 

 ■descending the eastern slopes, which are less steep than 

 the western, w^e passed through the same changes of 

 flora, in the reverse order, as those already observed 



The country at its foot is thickly studded with small 

 Baobabs and away to the east the open Acacia and 

 Bauhinia forest again prevails, and undoubtedly merges 

 farther south into the thorn-bush of Ovamboland and the 

 Acacia park-formation which extends far to the south of 

 Okahandya and Windhuk. 



I take this opportunity of acknowledging the effective 

 support which has been very kindlv given to the objects 

 of the expedition by Their Excellencies Sr. Capt. H. 

 de Paiva Couceiro, Acting Governor-General of Angola : 

 Herr Reglerungsrath Dr. Hintrager, Acting Governor of 

 German South-West Africa ; and the Hon. W. F. Hely- 

 Hutchinson, G.C.M.G., Governor of Cape Colony. 



H. H. W. Pearson. 



nossatncAes 



Ti'lt/rSa 



MODERN METHODS OF ILLUMINATION.^ 

 A GREAT change has come over the methods of light- 

 ing within the last few years. We have now at our 

 disposal means of lighting which would have seemed in- 

 credible a few years ago. Step by step with these 

 developments has taken place the progress of education 

 and the increase of printed matter, with the result that 

 we use our eyes to-day far more than in the past. Our 

 main object, therefore, should be to con- 

 sider the subject of illumination from 

 the point of view of the impression re- 

 ceived through the eye. After empha- 

 sising this aspect of illumination, Mr. 

 Gaster proceeds with a summary of 

 recent developments in electric light- 

 ing. 



Electric Glow-lamps. 



It has long been known that a 

 carbon filament glow-lamp could be 

 made to yield more efficient results by 

 bringing it to a higher temperature, 

 i.e. running it at a pressure higher 

 than that ordinarily utilised, but such 

 a gain in efficiency has only been found 

 possible at the expense of life and 

 durability. 



Within the last few years we have 

 seen the development of lamps with 

 filaments made of other and more re- 

 fractory materials, such as the Nernst 

 lamp, and the various metallic fila- 

 ments, such as osmium, iridium, tan- 

 talum and tungsten, &c. The two last- 

 named lamps, of course, now play a 

 great role in electric lighting. 



In addition, attempts have been made 



to improve carbon filaments in the 



United States by the graphitising pro- 

 on the other side. Passing the Huilla Mission — 1 cess of Mr. Howell, by the aid of which a consumption of 

 the scene of the botanical labours of Fathers Antunes and I 2-5 watts to 3 watts per candle was attained. Another 

 Dekindt — we arrived on May 13 at Chibia (4500 feet), : interesting attempt in this direction is the Hopfelt lamp, 

 where the proteaceous flora thins out and gives place in which the carbon filament burns in an atmosphere of 

 again to the open, dry forest, in which the Bauhinia and i mercury vapour, with, it is stated, a consumption near 

 Acacias in turn predominate. Henceforward the surface, 1^5 watts per candle. The Helion lamp, again, is believed 

 -frequently broken by tumbled heaps of gneiss and iron- to utilise a filament mainly composed of silicon ; it is 

 ;stone, 50 feet to 500 feet high, slopes gently down to the claimed to run for 1000 hours at i watt per candle, and 

 Cunene. From Gambos (4100 feet) the water-supply, after even in the open air, without requiring to be enclosed in an 



evacuated globe; but it has not yet come upon the market. 

 Perhaps the best known metallic filament lamps in use at 

 the present day are those utilising the metal tantalum 

 and those described by various names, but generally 

 believed to contain as the main constituent the metal 

 tungsten. Tungsten lamps are burned at a consumption 

 approaching 1 watt per candle-power, and are generally 

 stated to have a life, under good conditions, of 1000 burn- 

 ing hours. One great difficulty, however, has been the 

 manufacture of lamps of moderate candle-power for high 

 voltages, and capable of being used in any position ; very 

 recently, however, lamps having as low a candle-power as 

 25 or 30, and for pressures extending to 200 volts to 260 



PEffCYSLABE/V 



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I 



'the end of the rainy season (April), is meagre and its 

 quality bad, and the whole district is fever-stricken. The 

 •temperature becomes very high after mid-day, and whirl- 

 winds of great violence spring up very suddenly, and carrv 

 •columns of dust and other light objects to great heights. 

 Three hours by waggon from Houmbe brought us to the 

 Cunene marshes, which are here confined to the right 

 bank of the river. Owing to the unusually late rains 

 they were still nearly two miles wide, and it was with 

 great difficulty that a crossing to Fort Rogadas on the 

 opposite bank was effected. This stronghold is placed upon 

 the high calcareous cliff forming the left bank of the river. 

 Its neighbourhood, the scene during recent years of many 

 engagements between the Portuguese and the trans-Cunene 

 pvarnbo_ tribes, has become so extremely unhealthy that 

 it will in future be manned entirely by native troops. 



KG. 2086, VOL. Si] 



1 Abstract of a series of four Cantor lectures delivered by Mr. Leon 

 Gaster before the Royal Society of Arts and published in the Journal of the 

 Society for August 6, 13, 20, 27 ; September 3, 10. 



