May 28, 1903] 



NA TURE 



91 



radio-active properties after bubbling through strong 

 sulphuric acid, or caustic potash after passing over red-hot 

 copper, or through a narrow platinum tube kept at a white 

 heat ; it does not seem appreciably affected when sparks are 

 passed through it. 



'Jhe gas can diffuse through a porous plate, and by com- 

 paring its rate of diffusion with that of CO, through the 

 same plate, its density can be determined by Graham's law ; 

 preliminary measurements of this kind indicate that two 

 different gases are present, of which one has a density 

 about twice, the other between six and seven times that of 

 CO,. The gas obtained by boiling the water always diffused 

 faster than that procured by bubbling air through the 

 water ; it seems possible that in the latter case the gas may 

 get loaded with water-vapour to a greater extent than in 

 the former. 



A negatively electrified surface exposed to the gas be- 

 comes radio-active, the induced radio-activity dying away 

 to half its value in about forty-five minutes. Mr. Adams 

 has shown that a positively electrified surface also becomes 

 radio-active when exposed to the gas, though to a smaller 

 extent than if it had been negatively electrified ; an un- 

 electrified surface does not become radio-active. In this 

 respect the gas differs from the emanation from radium, 

 which, according to Rutherford, produces much more in- 

 duced radio-activity in an unelectrified surface than in a 

 positively electrified one. 



The rate of diffusion through a porous plate of the gas 

 obtained by bubbling air through distilled water containing 

 a trace of radium is not the same as that of the gas got by 

 bubbling through tap-water. 



If the gas is confined in a closed space its radio-activity 

 slowly diminishes. Mr. Adams found that the gas con- 

 tained in a vessel of about 300 c.c. capacity lost when not 

 e.xposed to an electric field about 5 per cent, of its activity 

 in twenty-four hours ; under a strong electric field the rate 

 of loss was doubled. Water drawn from the tap and left 

 exposed in a bucket for a fortnight gave off very little of 

 (he gas when subsequently boiled. I have not found any 

 of the gas in any of the numerous samples of rain and 

 surface water which I have tested. 



Prof. Dewar (to whom I am greatly indebted for assist- 

 ance and advice) was kind enough to subject the gas 

 obtained by boiling the water to treatment by liquid air. 

 Two samples were treated : one, containing about 80 litres 

 of gas, obtained from the coppers of the Star Brewery, 

 Cambridge, by the kindness of Mr. Armstrong (to whom 

 I wish to express my thanks), was passed slowly through 

 a bath of liquid air, and samples of the emergent gas 

 collected ; this on testing was found to have no radio- 

 activity, though it was strongly radio-active before passing 

 through the liquid air ; it is evident, therefore, that at the 

 temperature of liquid air the radio-active gas is frozen out. 

 The other sample, of 20 litres, prepared in the laboratory 

 was actually liquefied ; the liquid was then allowed to boil 

 away, the gas coming off at the commencement of boiling 

 was collected, and also that coming off when the liquid 

 had all but boiled away. On testing the samples for radio- 

 activity the former was found to be slightly radio-active, but 

 not nearly so much so as before liquefaction, while the 

 second was extraordinarily radio-active, its activity being 

 quite thirty times that of the original gas, thus showing, 

 as we should expect from its great density, that the radio- 

 active gas is much more easily liquefied than air. 



The liquid obtained in the preceding experiment had a 

 very strong smell of coal-gas. I must again express my 

 thanks to Prof. Dewar and Mr. Lennox for their kindness 

 ''n making these experiments. 



A discharge tube was filled with stronglv radio-active 

 gas obtained as above, and the spectrum was most kindly 

 investigated by Mr. Newall, who photographed it and 

 measured the lines ; no new lines were, however, discovered, 

 the lines present being mainly those due to hvdrocarbons. 



I add a list of the various specimens of 'water I have 

 examined ; yes, means that the water contains the gas ; no, 

 that it does not. 



Cambridge tap-water (yes). Rain water (no). Water 

 from ditch round Botanical Garden (no). Water from 

 Trinity College well, on the Madinglev Road (ves). Water 

 from artesian well in Mr. Whetharh's garden, Chaucer 

 Road (yes). Water from shallow well in same garden (no). 



NO. 1752, VOL. 68] 



Water from well at Star Brewery (yes). Artesian well in 

 Trinity Hall Cricket Ground (yes). Artesian well at 

 Girton (yes). Ely Town's water (yes). Birmingham 

 Town's water (yes). Ipswich Town's water (yes). 



In concluding this preliminary account I have much 

 pleasure in thanking my assistant, Mr. E. Everett, for his 

 help in this investigation. 



GEOGRAPHICAL RESEARCH. 

 T N the course of his presidential address at the recent anni- 

 ■*■ versary meeting of the Royal Geographical Society Sir 

 Clements Markham, K.C.B., F.R.S., outlined a scheme, 

 which is shortly to be put in operation by the Society, for the 

 purpose of encouraging geographical research. The plan to be 

 tried is the outcome of the afternoon meetings of the Society, 

 started in 1894, for the reading and discussion of strictly 

 scientific or technical papers. It is hoped that by the plan 

 outlined in the subjoined extract from the president's ad- 

 dress, the value of the afternoon meetings will be increased, 

 and the scientific side of geography will be developed. 



A permanent committee has been appointed to deal with 

 this department of the work of the Society, to be called 

 the " Research Committee." It will consist of those Fel- 

 lows, taken from the List of Referees (which includes 

 Fellows who have read papers, published books, or are 

 known to have a special knowledge of any department of 

 geography), who are most interested in, and best qualified 

 to deal with, the subjects which are embraced in geographi- 

 cal research, as distinguished from exploration, in all its 

 numerous branches. The committee will meet for the dis- 

 cussion of such results of investigation as may be brought 

 before it ; and the Council may be able to set apart a 

 moderate sum each year for the purpose of encouraging such 

 researches among the younger geographical aspirants. 



Among the numerous lines that research may take, the 

 following have been suggested : — 



New methods of surveying, mapping, or computing. 



Discussion of a definite problem of geomorphology {e.g. 

 analysis of a river system or a coast-line). 



Discussion of a definite problem of hydrography (e.g. 

 circulation of water in a restricted sea area). 



Discussion of a definite problem of meteorology {e.g. 

 modifications of general weather conditions by local features). 



Regional studies {e.g. synthesis of the geography of a 

 county or of a natural unit such as the Fens). 



Investigation of distribution {e.g. of some crop in rela- 

 tion to natural facilities and access to markets ; of former 

 forests in relation to existing boundaries ; of village and 

 town sites in a district). 



Mapping of distribution of plant associations in a given 

 area, or of a human disease in relation to climate and soil. 



History of the map of some country {e.g. the British 

 Isles). 



Investigation of evidence of physical changes within his- 

 torical times {e.g. the British coasts ; the desiccation of 

 continents). 



Discussion of the relation of land forms to military move- 

 ments in a selected area, or a chosen campaign. 



Discussion of the relation of land forms to the distribu- 

 tion of man ; to the distribution of animals in a^ny area. 



Geographical conditions affecting the development and 

 colonisation of any given region. 



Complete investigations from the geographical stand- 

 point of a limited area of unexplored or partially explored 

 territory. 



There is still ample room for exploration and expeditions 

 of discovery. We have scarcely yet laid down the great 

 lines of the world's geography, and there is work for genera- 

 tions to come in filling in the details, though future explora- 

 tion must become more and more exact and scientific in its 

 characters. But we ought also to encourage research, for 

 which exploration furnishes the raw material. By the plan 

 now in contemplation, we shall develop the purposes of the 

 List of Referees by constituting the Research Committee ; 

 and we shall develop further the object of the afternoon meet- 

 ings by promoting research, the results of which will place 

 the meetings on a more assured and regular system, by 

 creating the necessity for their being more frequent and at 

 fixed intervals. 



