TRANSAC'J'lUNS OF SECTION B. 389 



recently been found that enzymes or ferments whicli are mainly responsible for 

 the chemical changes taking place in the plant are inhibited by smoke pollution. 

 This causes a distinct cutting down of the intensity of colour in our plants ; it 

 also handicaps plants from forming any reserves either in the form of bulbs 

 or seed, and considerably reduces the germination capacity and energy of seeds, 

 thus generally lowering the vitality of plants and preventing them from putting 

 up a fight against adverse conditions. 



Professor Fernand Ranwez (University of Lonvain). — Very many works and 

 factories emit smoke so abundantly as to cause harm to vegetation. Some of 

 them also emit gases which are noxious to plants, and so blight the neighbouring 

 country. 



When the fumes are very pronounced the destructive effects are clearly seen, 

 as, for example, near those works which pour out large quantities of sulphur 

 dioxide. In the immediate neighbourhood of such works the plants exposed to 

 the frequent action of the gas have their leaves scorched, while trees lose their 

 leaves and show many dead branches, the action of the gas gradually killing them 

 entirely. 



Though these are the most acute symptoms, there are many others far less 

 pronounced, every intermediate condition being observable between plants which 

 exhibit only a slightly checked development and those which die from evident 

 poisoning. Factory smoke and the damage it produces raise frequent complaints 

 from neighbouring landowners and farmers who are, or believe themselves to 

 be, injured, and consequently the courts and experts have to decide the following 

 questions : (1) Has the land of such a person suffered damage, and if so, to 

 what extent ? (2) Is the damage wholly or in part the result of the smoke from 

 the factories complained of ? The solution of these questions necessitates a com- 

 parative study of the general conditions of cultivation and an examination of the 

 actual smoke deposits both on the damaged lands near the works "which emit the 

 noxious vapours and districts various distances away. 



If perhaps the scorched leaves exhibit some characteristic aspect, there may 

 exist some cause other than mere smoke capable of producing such damage. 



The damage is often limited to diminished growth and spread of vegetation, 

 or to a slow withering, and many causes besides smoke produce these effects, 

 such, for example, as faulty cultivation and sour or poor soil. 



Vapours often leave their imprint, as, for example, sulphur dioxide (one of 

 the commonest destructive agents), which can be recogjiised in plants in the 

 form of sulphate. But plants usually contain sulphates in very varying pro- 

 portion even without the direct action of the gas, so it follows that the discovery 

 of more or less characteristic forms of damage, the observation of the diminution 

 of the spread and growth of plants, or their destruction, the presence of an 

 increased quantity of sulphates or other compounds which could have arisen 

 from vapours do not sufficiently prove the destructive effects of gas when they 

 are considered by themselves alone without all contingent circumstances. The 

 observations only yield proof when they are contrasted with similar ones taken 

 with due care on plants of neighbouring districts. To make such comparative 

 experiments one must describe round the offending factory a series of con- 

 centric circles of ever-increasing radius, and then see (1) whether in the more 

 distant regions the vegetation presents normal features, (2) whether it exhibits 

 abnormalities on approach to the factory, and (3) whether such abnormal 

 features become proportionately more marked as the plants become more 

 exposed to the action of the gas. 



In all such observations account must be taken of the general cultural con- 

 ditions of the compared areas. Mere distance from the point of origin is not, 

 however, the only factor on which the noxious action of such vapours depends, 

 for many other factors come into play, such as the prevalence of wind, humidity 

 of the atmosphere, &c. 



(iv.) Improvements in Domestic Fire-Grates. 



Mr. A. Vernon Harcourt described a type of domestic grate, which he had 

 designed and had in use in his own residence during many years, for burning 

 coal or coke, the extended use of the latter of which as a household fuel 

 would, in his opinion, be a most advantageous means of solving the domestic- 



