NATURll 



165 



THURSDAY, DECEMBER 23, 18S0 



THE FOGS OF LONDON 



LAST \veek Mr. Scott Moncrieff described in our 

 columns a method of all but entirely eliminating 

 smoke from the atmosphere of London, and thus abolish- 

 ing that most venerable of our institutions — Fog. And 

 in a recent number Dr. Siemens showed how our existing 

 grates could be made to give out a maximum of heat at a 

 minimum of expense and an entire absence of smoke. It 

 may therefore be of some interest to inquire briefly into 

 the latest theories as to the causes and consequences of 

 this hideous incubus which renders residence in London 

 a terror to so many. 



Fogs are supposed to form a constituent part of the clima- 

 tology of the British Islands from which there is no escape; 

 and in certain strictly local climatologies, such as that of 

 London, where the aggregation of human beings is alto- 

 gether unprecedented, they now and again acquire an 

 extraordinary intensity and persistency, and are attended 

 with consequences so disastrous and fatal as to press 

 urgently on Parliament the necessity of legislation towards 

 the mitigation of the evil. 



In illustration of this, reference may be made to the 

 influence on the mortality of London exercised by the 

 fog which prevailed there from November, 1879, to 

 February, 18S0, which was so remarkable both for its 

 denseness and protractedness, as to constitute it one of 

 the most memorable fogs on record. The question has 

 been investigated by Dr. Arthur Mitchell, and the results 

 recently published in the Journal of the Scottish Meteoro- 

 logical Society. 



The increase in the death-rate was truly enormous, as 

 these figures, giving the whole mortality for each of the 

 seven weeks ending February 21, show — 1754, 1730, 1900, 

 2200, 3376,2495, and 2016 ; in other words, several thousand 

 persons fell victims to the disastrous fatality of this great 

 fog. An examination of the figures in the Registrar- 

 General's Reports shows that no approach to so large an 

 increase in the death-rate showed itself in any of the 

 other British large towns, and in none of these did fog of 

 a noteworthy character occur. Of all diseases, asthma 

 was most directly influenced in its fatality by the fog ; 

 for as the density of the fog increased so did the deaths 

 from asthma, and as the fog abated, relief came at once 

 to the asthmatic, and the death-rate instantly fell. Thus 

 the mortality rose to 220 per cent, above the average 

 during the week of densest fog, but as the fog gave way 

 the mortality fell to 40 per cent, below the average. 

 Bronchitis, pneumonia, pleurisy, and other lung diseases 

 appeared also with an enormously increased fatality, the 

 mortality from bronchitis rising during the week when the 

 fog was at its worst to 331 per cent, above its average. In 

 the case of these diseases however the relief did not come 

 instantaneously with the cessation of the fog, but injuries 

 of a more] permanent nature appear to have been sus- 

 tained which kept the death-rate at a high figure for some 

 time after the fog had finally disappeared. Whooping- 

 cough exhibited these characteristics in even a still more 

 pronounced manner. The pernicious effects of the fog 

 lingered still longer in the system; so that while the 

 Vol. XXIII. — No. 582 



death-rate rose during the worst week of the fog to 182 

 per cent, above the average, four weeks thereafter it had 

 fallen no lower than 74 per cent, above the normal 

 mortality of whooping-cough. It is singular, and particu- 

 larly to the medical profession profoundly interesting, that 

 deaths from croup, diphtheria, and rheumatism did not 

 show any distinct relation to the fog. As regards the other 

 diseases, the deaths from which are registered, they 

 equally did not appear to show any steady connection 

 with the fog's varying denseness and persistency. 



This pernicious and deadly character of fog on persons 

 suft'ering from these diseases is not due to fog as such, but 

 to the noxious qualities imparted to it by our large towns. 

 Dr. Angus Smith has shown that the air of Manchester 

 during an extremely dense fog contained 20'85 per cent. 

 of oxygen, or one-tenth per cent, less than the normal 

 quantity. The pernicious character of fog however is to 

 be traced not so much to this slight diminution of atmo- 

 spheric oxygen as to the presence of positively deleterious 

 substances. 



The smoke which issues from our dwelling-houses 

 contains, in addition to solid soot, also gaseous carbonic 

 acid, sulphurous acid, carbon monoxide, sulphide of 

 ammonia, and sometimes minute traces of arsenic. More- 

 over the soot does not consist of particles of carbon only, 

 but carbon saturated with tarry matters, sulphur and 

 ammonia compounds, &c. Smoke from manufactories is 

 usually more completely burned than that from dwelling- 

 houses, and is therefore less deleterious. In many cases 

 however manufactories pour out into the air their own 

 specific hurtful gases. Of these gases the more pernicious 

 are mineral acids, especially sulphuric and hydrochloric 

 acids, sulphuretted hydrogen, sulphur dioxide, and oxide 

 of arsenic. Gases rising from decaying animal and 

 vegetable matter in waste heaps and in faulty sewers also 

 lend their aid in the contamination of the atmosphere of 

 towns. In the neighbourhood of various manufactories 

 solid impurities crowd the air, resulting in a denseness of 

 fog in these restricted localities with an accompanying 

 suffering and fatality elsewhere unknown. 



In February last we drew attention (Nature, vol. xxi. 

 P- 355) to the question of fogs and the general atmospheric 

 conditions under which they are generated, when the 

 importance in discussing the question of fogs of a careful 

 study of the anticyclone and its accompaniments was 

 adverted to. Indeed it is in the highest degree probable 

 that all cur memorable great fogs are intimately connected 

 with the anticyclone, being found towards their outskirts 

 or rather in the debatable region between the cyclone and 

 the anticyclone. They arise from the diffusion of the 

 vapour brought up by the cyclone outwards and through 

 the colder and drier air of those parts of the anticyclone 

 contiguous to it, where it is condensed into immense 

 breadths of fog stretching several hundred miles in 

 length. 



The two features of the anticyclone to which more 

 special attention is directed are these : (i) the calmness 

 or comparative calmness of the air ; and (2) the slow 

 downiuard general movement of the atmospJiere over the 

 region covered by the anticyclone, and a general outward 

 mo\ement in aU directions towards surrounding regions 

 as we near its outskirts. 



Consider now] this feature of the anticyclone in its 



