442 



NA TURE 



[Alarck 7, 18S9 



carbonic acid in it. Dr. W. J. Russell found fro ii experi- j 

 ments made in the City of London a few years .'is^o, that I 

 on one day the carbonic acid had increased to 141 parts j 

 in 10,000 of air — that is, there was more than three and I 

 a half times the average amount present. 



The question will naturally be asked, whether we can- 

 not check this increase of carbonic acid in London air; 

 and, in reply, it may be said that we can ; partly by stopping 

 the enormous volumes of sooty smoke belched out daily 

 from hundreds of thousands of chinmeys in the metropolis; j 

 and, partly, by having more open spaces, &c. 



Jt is well known that the crowding of many people and 1 

 animal life of all sorts, upon a small area of land, increases 

 the production of carbonic acid, whether it be from 1 



respiration or from coal-burning ; and it is almost indis- 

 putable that the latter produces the well-known black fogs 

 and yellow fogs. 



That these black fogs and yellow fogs — to which 

 London and other large towns are liable in the winter — 

 have a most injurious effect upon human beings and all 

 animal life, and vegetation also, cannot be doubted, since 

 we see the death-rate largely increased during the preva- 

 lence of black fogs; and of late years the more delicate 

 plants, and indeed the strong ones', both at the Botanical 

 Gardens, Regent's Park, and at Kew, have suffered much 

 from the same cause. 



Two things are to be briefly shown in this paper : 

 (i) the general thickness and density of the atmosphere 



Sketch Map op a Portion of London: 



Measuring Points shown bv Black Dots. 



over London during the winter ; and (2) the amount of 

 artificial light used during the prevalence of black or dark 

 yellow fogs in various parts of London. 



In connection with this subject various observations 

 were taken in London during the winter of 1887-88, and 

 tiie results are given below. 



Before proceeding further, we may note that London 

 was \ery free from fogs during the winter of 1807-88 — 

 a lact which was probably, to a certain extent, due to the 

 light rainrall, and the unusual dryness, in consequence, of 

 the great plain or valley of the Thames. This was the 

 case not only in London, but in Manchester, Leeds, 

 Liverpool, and elsewhere. 



(1) As regards the general thickness and density of 

 L(„i.(..t<n air. The sketch plan of a portion of London 



will show that Primrose Hill; — which is about 219 feet 

 above the sea-level — was the point selected for (let us say) 

 measuring from. 



Three hnes, which embraced the measuring -.points 

 fixed upon, were taken over London, these lines being re- 

 spectively the south-west line to St. Mary Abbot's Church, 

 Kensington ; the south line to the Clock Tower, Houses 

 of Parliament ; the south-east line to St. Paul's Cathedral. 

 One more line was taken towards the country : this we 

 will rail the north line to St. John's Church, Hampstead. 

 Intermediate measuring points were taken on all these 

 lines, church spires or towers, &c., being selected as 

 the most conspicuous objects that could be, seen from 

 Primrose Hill. 



The distance of all these intermeiiate measuring points 



