ON THE EFFECTS OF URBAN FOG UPON CULTIVATED PLANTS. 141 



able to collect by observation, correspondence, and experiment, 

 but to indicate only the lines of inquiry, in the hope of obtaining 

 criticisms likely to be of value in the further prosecution of the 

 work. It will not be possible or desirable to prepare any detailed 

 report till another year has elapsed. 



My observations so far deal almost entirely with plants 

 cultivated under glass. 



It will be convenient, for the purposes of this report, to take 

 the several lines of inquiry, and to deal with them in successive 

 paragraphs. 



I. Urban Fog and Country Mist. — In an inquiry into the 

 action of so complex a product as urban fog, it was of the greatest 

 importance to obtain reliable data as to the effect on vegetation, 

 if any, of pure country mists, uncontaminated by smoke. It was 

 impossible for me personally to make the observations needful to 

 establish the injurious or other action of mist upon plants ; but, 

 by the courtesy of correspondents in country districts, quite away 

 from areas of smoke genesis, it would appear, so far as observa- 

 tions are as yet to hand, that little or no injury to stove or 

 conservatory plants arises from this cause. Indeed, pure mists 

 would seem to be beneficial to certain classes of cultivated plants* 

 In those instances in which any injury obtained, it was, in most 

 cases, referable to some other cause. The establishing of this 

 point is of great importance, since foggy weather is so frequently 

 attendant upon spells of frost, and it has been frequently 

 suggested that the increased stove heat needful to maintain the 

 requisite temperature would have a harmful action. Indeed, I 

 was quite prepared to find this to be the case at the outset of the 

 inquiry. My own observations during cold weather in London 

 without fog, and the evidence to hand from a distance, as to frost 

 with and without mists, point to the fact that, with proper pre- 

 cautions, no appreciable damage is done to plants. 



In general, the same remarks apply to small towns away from 

 manufacturing areas. With the increase in size of the towns, 

 the conditions more nearly approximate to those of London. 

 The fog leaves the well-known deposit of filth on glass-houses 

 and evergreen foliage ; and if such districts escape the more 

 serious effects observable in or near the larger smoke-producing 

 areas, it is due to the relatively small concentration of the im- 

 purities in those fogs. It seems to me desirable to obtain 



