May 12, 1898] 



NATURE 



41 



that the yield of a few trees cannot be remunerative, and 

 only large areas can hope to make the industry a paying one. 

 (3) It produces a good class of rubber, second only when well 

 prepared to the best Para rubber. For this there is a steady 

 and continuous demand. The yield per tree is apparently small, 

 but a return is obtained earlier than from any other rubber 

 plant. With thick planting and judicious thinning as the trees 

 grow up, it may be possible to increase the yield hitherto re- 

 corded ; while with skilful treatment the permanent trees may 

 be tapped twice yearly, and last in a productive state for fifteen 

 to twenty years. (4) In spite, therefore, of the apparent want of 

 success which so far has attended experiments with Ceara rubber 

 plants in Ceylon and other countries, the increasing importance 

 of rubber as an article in large demand in all civilised countries 

 at good prices, suggests a reconsideration of the merits of this 

 interesting plant. In many of our Colonies possessing a dry 

 climate and a poor stony soil, it is possible that large areas 

 could be profitably occupied with Ceara rubber trees so grown 

 as to provide annual crops for tapping. 



Mr. D. a. Gilchrist, Director of the Agricultural Depart- 

 ment of the University Extension College, Reading, has issued 

 his fourth annual report upon the field experiments carried 

 on during last year. Since 1894 field experiments have been 

 made at the College, and the results have been of distinct service 

 to agriculturists. The County Councils of Berkshire, Dorset, 

 Hampshire and Oxfordshire co-operate with the College in this 

 work through their Technical Instruction Committees ; sub- 

 sidies being granted by these bodies to the College to meet the 

 expenses. During the season 1897 the work included the test- 

 ing of manures on most of the principal farm crops, and a 

 further development was made in the direction of carrying out 

 field experiments of a more continuous character, such as the 

 effect of manures, applied at the beginning of a rotation of 

 crops, throughout the whole rotation. The results of all field 

 experiments are of much more value in the locality in which 

 they are carried on than elsewhere ; nevertheless, Mr. Gil- 

 christ's report gives much useful information as to the effects of 

 various manures on different crops, under very different con- 

 ditions of soil ; and from this, tolerably safe general conclusions 

 may be drawn. The Agricultural Department of the University 

 Extension College at Reading may indeed be compared with 

 the agricultural experiment stations of Canada and the United 

 States, for it is performing, so far as it is able, the functions of 

 those institutions by conducting inquiries of value to agricul- 

 turists, and acting as a reference bureau. 



We have received from P. K. Kozloff, member of the last 

 Russian Tibet expedition, a very interesting contribution to 

 the Lob-nor controversy. It is issued by the Russian Geo- 

 graphical Society as a pamphlet ("Lob-Nor"), and contains 

 the Russian traveller's remarks concerning the lakes discovered 

 by Sven Hedin, for which the Swedish explorer claims to be 

 the true Lob-nor ; while the lake Kara-koshun-kul, discovered 

 by Prjevalsky, and described by him as the Lob-nor, would be, 

 in Sven Hedin's opinion, but a secondary and temporary basin. 

 P. K. Kozloff gives in his pamphlet all materials which may 

 enable the reader to come to an independent opinion, namely, 

 a map of the region, embodying the Russian surveys and 

 Hedin's discovery ; a copy of the Chinese map upon which 

 Richthoffen and Hedin based their argumentation ; and 

 abstracts from Prjevalsky's, Pyevtsoff's, Bogdanovich's, Hedin's, 

 and Kozloff's descriptions of the Lob-nor region. The map 

 already shows to what extent Hedin's claims are admissible. 

 The author then discusses Richthoffen's and Hedin's arguments. 

 The Chinese map, which gives to the Lob-nor a more northern 

 position than the position occupied by Prjevalsky's Lob-nor, 

 Kozloff shows, is wrong, because it gives to the junction of 

 NO. 1489, VOL. 58] 



the Tarim with the Konche daria (Airylgan) a much more 

 northern position than was found already in 1765 by the 

 Jesuits, and confirmed since by General Pyevtsoff. In fact, 

 most of the positions on the Chinese map have more northern 

 latitudes than thp real ones. The lake Khas of the 

 same map, with which Richthoffen and Hedin wanted to 

 identify Prjevalsky's Lob-nor is, beyond any possible doubt, 

 the lake Ghas of Prjevalsky, situated beyond the Nutsitu ridge 

 marked on the Chinese map. As to the chain of four lakes 

 discovered by Hedin, of which the southern only had been 

 previously visited by Kozloff, they have been formed by the 

 Konche daria, which, coming from the north-west, is con- 

 tinually shifting its bed in its lower part towards the right, 

 i.e. westwards. The desert in the north of the Lob-nor has 

 been formed through that shifting of the bed of the Konche 

 daria, and the chain of lake-shaped enlargements of the old 

 bed of the Konche daria, the Ilek, for which Hedin claims to 

 be the historical Lob-nor, is nothing but a temporary form- 

 ation, due to the rightward shifting of the river bed. Kozloff 

 develops this hypothesis with much skill, and concludes that 

 Prjevalsky's Lob-nor (the Kara-koshun-kul) must have extended 

 much further northwards and eastwards ; but the lowest part 

 of the depression, which is occupied by this lake, always was 

 the historical Lob nor. 



The additions to the Zoological Society's Gardens during the 

 past week include two Sooty Phalangers (Trtchosurtis ftili- 

 ^inostts, (J 9 ) from Tasmania, presented by Mr. A. Walley ; four 

 Common Vipers ( Vipera berus), British, presented by Mr. J. 

 Amos ; a Salvadoris Cassowary {Casuarius salvadorii) from 

 New Guinea, a Glaucous Macaw {Anodorhytichus glaucus) from 

 Paraguay, a Common Chamiieleon {Chamaleon vulgaris) from- 

 North Africa, deposited ; a Common Zebra (Eqiius zebra, 9 ), 

 bred in Amsterdam ; six Garganey Teal (Querquedula circia,. 

 3 <J . 3 9 ). European, purchased. 



OUR ASTRONOMICAL COLUMN. 



The Spectrum ok Hydrogen in Nebul.'e. — If hydrogen 

 gas in a Geissler tube be examined spectroscopically, the 

 brightest line observed is Ho. If, on the other hand, the lines- 

 of hydrogen in nebulre be examined, H3 may sometimes be well 

 seen, while Wa, the C line, can scarcely be detected. To- 

 account for this apparent change of intensity several investiga- 

 tions have been made, and as long ago as 1868 Lockyer and 

 Frankland showed that the hydrogen spectrum could be reduced 

 to the single line H;8 under certain conditions of temperature 

 and pressure. Prof. Scheiner has recently investigated the 

 question of the luminosity of hydrogen in the nebulae {Astro- 

 physical Journal, No. 4, April 1898), and he has attempted to 

 introduce "circumstances approximating to those under which 

 the nebulas emit light " to find out whether objective changes 

 can be produced in the spectrum of hydrogen in an attenuated 

 state, or whether the subjective weakening of the light is the 

 determining factor, and if so to what extent. By exciting 

 tubes filled with hydrogen in the field of a Tesla high tension 

 transformer, the space surrounding them having a temperature 

 of about - 200^ C, Koch's investigations were confirmed that 

 the spectrum of hydrogen did not change when the surrounding 

 temperature was reduced as low as - 200° C. Prof. Scheiner 

 next investigated the physiological disappearance of the Ha 

 line, and without entering on the procedure adopted, which is 

 described in the journal referred to above, we will limit our- 

 selves to the result. The absence of the Ha line in the hydrogen 

 spectrum is due to physiological reasons, and it is consequently 

 not permissible to deduce from this peculiarity of the hydrogen 

 spectrum in the nebulte any conclusion whatever concerning the 

 physical conditions under which the light emission of these 

 celestial bodies takes place. Whether certain nebulas may not 

 prove exceptions to this rule, is to be left an open question ; it is 

 certainly not impossible that such may be the case. 



