442 



NA TURE 



[March 12, 1908 



only modified the dosage, and he adds his testimony 

 to the great value of the drug. 



This method, should nothing supersede il, will Ihus 

 hecomo almost as valuable as ihat of quinine in the 

 treatment of malaria. In Koch's words, " Daraus 

 geht doch abcr mit aller Bestimmtheit hervor, dass 

 durch eine geeignete Atoxyl behandlung schr vielen 

 Schlafkrankei. das leben gerettet warden kann." 



(4) Destruction of tsetse-flies. — This, so far as we 

 know at present, is not directly practicable, but the 

 (lies can be driven away by cutting the jungle. The 

 making of clearings where the natives most frequent, 

 such as at watering places, river fords, and around 

 villages, will certainly be beneficial. 



For the present, then, we have at our disposal 

 methods the results of which we shall soon learn. In 

 conclusion, it is, I think, certain that when some of 

 the disputed points indicated above are settled the 

 campaign again ;t the disease will be carried out with 

 greater efficiencv because based on more certain 

 knowledge. ' J. W. W. S. 



WATER VAPOUR IN THE MARTIAN 

 ATMOSPHERE. 



ONE of the most telling arguments which has been 

 used against the possibility of the planet Mars 

 being habitable has been that spectroscopists have 

 failed to detect with certainty the presence of water 

 vapour in the planet's atmosphere. It now seems 

 probable that this objection will have to be aban- 

 doned, for, in a telegram recently received by Sir 

 Norman Lockyer, Prof. Lowell announces that Mr. ' 

 Slipher has got on repeated plates — specialty pre- 

 pared for this research — the water vapour bands a 

 and near D stronger in the spectrum of Mars than in 

 that of the moon at the same altitude. 



Should Prof. Lowell's further researches confirm 

 it, this result is one of the most important links in 

 the remarkable chain of evidence for a habitable 

 Mars. The photography of the canals was a great 

 step forward, but the presence of these features was 

 unconvincing unless it could be proved that the 

 water to fill them in their proper seasons was avail- 

 able. Similarly, the seasonal increase and decrease 

 in the dimensions of the snow-caps were thought to 

 be conclusive evidence for the presence of water until 

 the frozen carbon dioxide theory was advanced, 

 although this theory left unexplained the ill-defined 

 edges of the disappearing snowfields. But, so far as 

 our present knowledge goes, it is difficult to see how 

 carbon dioxide is able to produce the intensification 

 of the water-vapour bands in the spectrum of the 

 l)lanet's atmosphere. 



For many j'ears, in fact since the actual existence 

 of permanent features on the planet's surface was 

 established, this question of water vapour — of the 

 existence of a substance capable of producing clouds 

 and mists — has been one of the chief points of con- 

 tention among areographers. .So far back as 1863 

 Sir Norman Lockyer, in a communication to the 

 Roval .Astronomical Society (Memoirs, vol. xxxii., 

 p. 179, 1863), describing' his observations of Mars 

 during the opposition of 1862, stated that " although 

 ihe complete fixity of the main features of the planet 

 lias been thus placed beyond all doubt, daily — nay, 

 liinirly — changes in the detail and in the tones of the 

 different parts of the planet, both light and dark, 

 occur. These changes are, I doubt not, caused by 

 the transit of clouds over the different features." The 

 drawings accompanying the memoir illustrated the 

 changes mentioned, and confirmed the suspicions of 

 cloud effects noticed by .Secchi in 1858. But the 



NO. 2002, VOL. yj'] 



assumption that these effects were caused bv clouds 

 and mists entailed the assumption of the presence of 

 water vapour in the planet's atmosphere, and the 

 spectroscopic evidence for this has hitherto been too 

 indefinite. Suspected by Huggins and \'ogel in 

 1867 and 1873 respectively, its presence was nega- 

 tived by the subsequent spectroscopic researches of 

 Campbell and Keeler, but now it appears certain, 

 from this latest result from the Lowell Observatory, 

 that water vapour is one of the concomitants of the 

 Martian atmosphere. 



In his recent book, "Is Mars Habitable?" re- 

 viewed by Dr. Lockyer in Nature for Februarv 13 

 (P- ii7)> Dr. Russel Wallace insisted on the absence 

 of spectroscopic evidence as a strong argument 

 against the presence of water vapour. This objec- 

 tion is now removed, and once more it becomes 

 reasonable to suppose that the Martian surface is, at 

 least to some extent, supplied with that compound 

 which, to terrestrial minds, is one of the essentials of 

 habitability. At the same time, the theories advanced 

 by Prof. Lowell to explain the remarkable variety of 

 appearances and changes from season to season, dis- 

 closed by his wonderful observations, have received 

 support ttx)rtliv of their brilliant conceptions. 



\\"ILLI,AM E. ROLSTON. 



NOTES. 



In an announcement in last week's N.\tl're it w;is 

 stated that Prof. Kanierlingh Onnes had succeeded in 

 liquefying helium. It should have been stated that the gas 

 was solidified, no intermediate liquid stage being observed. 

 The demonstration was made in the presence of Prof. 

 H. A. Lorentz and Prof. J. P. Kuenen, both of the Uni- 

 versity of Leyden. The method adopted is described by 

 the Leyden correspondent of the Daily Tclegrapli 

 (March 10) as follows, and is the same as that used with 

 success by both Sir James Dewar and Prof. Olszewski. 

 The only noteworthy point is the large amount of helium 

 used for the instantaneous e.xpansion. " To make this 

 experiment," Prof. Onnes says, "I placed a tube with 

 thick sides, containing a thinner one for extra protection 

 against external warming influences, in a vessel filled witli 

 liquid hydrogen, at —434° F., and in this tube about one 

 and a half gallon of helium was compressed under 100 

 atmospheres. On allowing expansion to a lower tempera- 

 ture a cloud appeared, which increased as the expansion 

 in vacuo continued. Out of the nebulous mass a white 

 floeculent substance gathered in the inner tube, where — 

 although the tube was well closed — it evaporated within 

 twenty seconds. Some solid substance, however, was left, 

 the pressure in the tube meanwhile rising to one atmo- 

 sphere, and when the valve was opened and the pressure 

 was reduced this substance exhaled almost immediately, no 

 sign of liquefaction being observable. The substance which 

 remained at a temperature of —434° F. was solid helium." 

 We are glad to be able to print the telegraphic message 

 sent to Sir James Dewar by Prof. Onnes on March 5, and 

 Sir James Dewar's reply to it : — Prof. Onnes to .Sir James 

 Dewar, Royal Institution, London : " Converted helium 

 into solid. Last evaporating parts show considerable 

 vapour pressures, as if liquid state is jumped over." Sir 

 James Dewar to Prof. Onnes, University, Leyden : " Con- 

 gratulations. Glad my anticipation of the possibility of 

 the achievement by known methods confirmed. My helium 

 work arrested by ill-health, but hope to continue later on." 



The council of the British .Association has nominated 

 Prof. J. J. Thomson, F.R.S., as president of the associa- 

 tion for the meeting to be held next year in Winnipeg, 



