December 29, 192 1] 



NATURE 



573 



coals, as the temperature rises, the rate of absorp- 

 tion of oxygen increases. It is this chemical com- 

 bination of the coal substance with the oxygen of 

 the mine air which causes underground hrcs, and 

 it follows that coal in a powdered or finely divided 

 state, presenting a large air surface, is the most 

 readily subject to heating. The scientific investi- 

 gation of the phenomena surrounding the self- 

 heating of coal has made rapid strides during the 

 past ten years, and much credit is due to 

 those responsible for the patient research 

 work carried out at the various coal owners' 

 research laboratories, chief amongst which is 

 that of the Doncaster coal owners, estab- 

 lished at Bentlev Colliery in 191 3, and lately re- 

 moved to Birmingham University. A summary 

 of the work accomplished was recently given in 

 a paper read by the director. Dr. J. S. Haldane 

 (Transactions of the Institution of Mining Engin- 

 eers, vol. 53, pp. 194, etc.). 



By accurate measurement of the relative ab- 

 sorption of oxygen by different coal seams it 

 has been found that there is a very wide diver- 

 gence in capacity. The Welsh anthracites and 

 steam coals, for example, are found to have a 

 small, definite capacity for oxygen which is not 

 altered bv increase of temperature, and these 

 cannot, therefore, fire spontaneously. The same 

 properties are found in most of the Durham coal 

 seams, and it is well known that these two coal- 

 fields are practically immune from spontaneous 

 combustion of coal. 



A very close study has also been made of the 

 changes in the composition of mine air brought 

 about by the self-heating of coal, with the result 

 that by a system of analysis it is now possible 

 to obtain an earlv indication of the presence of the 

 self-heating of anv coal seam. It will be ap- 

 parent, therefore, from a practical point of view, 

 that the fullest information should be available as 

 to the chemical and physical phases of self-heat- 

 ing, in view of the changes that are constantlv 

 taking place in the conditions of mining coal. 

 The working of the deeper seams, with conse- 



quent increase of pressure due to superincumbent 

 strata, as well as increased temperature, is bring- 

 ing factors into play which will undoubtedly in- 

 crease the tendency to spontaneous combustion. 

 This is very noticeable in the case of the extension 

 and development eastwards of the Midland coal- 

 field in Yorkshire, where the Barnsley Bed Coal 

 is being worked at increasing depths. The thick- 

 ness of the seam vanes from 8 ft. to 11 ft., and 

 it is not practicable to extract the whole of the 

 coal, owing to the danger arising from falls 01 

 roof. The depth of the seam varies from 600 to 

 900 yards, and the temperature of the workings 

 is considerable. The result of these conditions is 

 to render the seam liable to spontaneous com- 

 bustion, contrary to what prevails in the extensive 

 workings to the west, where the seam is shallower. 

 X'arious remedies have been suggested from 

 time to time for dealing with the occurrence of 

 spontaneous combustion. One well-known man 

 of science has suggested that the oxygen content 

 of the mine air should be reduced by mixing inert 

 gases with the ventilating current, but such a 

 course cannot be regarded as practicable. The 

 application of hydraulic stowing has also been 

 suggested, the principle being to replace the coal, 

 contemporary with its extraction, by sand packing 

 flushed into the workings from the surface, thus 

 effectually filling up the wastes and excluding all 

 air therefrom. Whilst this method of working 

 has been utilised with success to a limited degree 

 in Fifeshire, it is not economically possible of 

 general adoption. One of the conclusions arrived 

 at by the recent Departmental Committee on 

 Spontaneous Combustion was that, generally 

 speaking, the methods of working in vogue in 

 the various districts where liability to spontaneous 

 combustion exists are those best calculated to get 

 the coal with the least danger of fire, and to give 

 the greatest facilities for dealing with outbreaks. 

 This expression of opinion is not only compli- 

 mentary to the mining profession, but also satis- 

 factory to members of the public interested in the 

 safetv of mines. 



Countries as Personalities.^ 

 By Prof. H. J. Flelre. 



'"PO emphasise the State as the most important 

 -*- human grouping on the large scale leads us 

 so far astray that even some serious students of 

 social psychology try, with obvious ill-success, to 

 discuss the psychology of whole nations like 

 France, England, and Germany. The very in- 

 adequate justification is that a political group like 

 a nation-State usually has one official language 

 and tries to organise one educational system and 

 thus endeavours to develop a common measure of 

 social heritage and early experience to unify its 

 population. As a matter of fact, unity of lan- 



1 Abridged from a citizens' lecture delivered at Edinburgh on September 12 

 during the meeting of the British Association. 



NO. 2722, VOL. 108] 



guage within a State is not so common as one 

 imagines. Spain has Basque, Catalan, and Gal- 

 ician ; France has Basque," Provencal, Breton, 

 Flemish, German, besides her dialects related to 

 Languedoc and Langue d'oil. Germany has many 

 dialects and also W endish and Yiddish ; Finland 

 has Swedish and now also a Lapp element, and 

 so on ; while Switzerland has built successfully 

 upon toleration of language diversity. This illus- 

 trates the diversity of biological units even within 

 the most modern States, while the very noticeable 

 trend in the treaties towards rearrangement of 

 Central Europe on a language basis emphasises 

 the fact that the biological unit has been' uneasy 



