1870.] Air-pollution by Chemical Works. 339 



of works. A determination was then made of the amounts of mu- 

 riatic and of sulphuric acids collected by the snow and by the rain, 

 and these were compared with the distances at which the samples had 

 been obtained. It was seen that the amounts diminished in even 

 ratio with the increase of distance. Probably a sufficient number of 

 experiments of this nature have not yet been made, firmly to esta- 

 blish the law ; for the undulations of the ground, the position of 

 trees, and any objects which interfere with the uniform motion of 

 the air, affect the even deposition of the acid vapours. More ex- 

 periments, it was said, were about to be undertaken in order to esta- 

 blish the law on a wider basis. Information on the third point may 

 be usually obtained at some neighbouring observatory. In the case 

 of St. Helens the returns of the direction of the wind, published at 

 the Liverpool Observatory, on Biclston Hill, were depended on. 



Fourthly, the amount of acid vapour discharged from each factory 

 in a given time can be known by periodical examination of the gases 

 which are passing up the various chimneys of the works. This is 

 already done as far as the alkali-works are concerned under the pro- 

 visions of the Alkali Act. In the cases of copper-smelting works, 

 glass-works, and others where systematic inspection has not been 

 carried on, the amounts of acid vapour thrown into the air can be 

 calculated from the materials used in the manufacturing processes 

 carried on. 



The acid vapours discharged from the various works in the 

 St. Helens district are: — From ten alkali-works, — muriatic acid, 

 sulphuric acid, sulphurous acid, nitrous acid, chlorine, coal smoke ; 

 from nine glass-works, — muriatic acid, sulphuric acid, sulphurous 

 acid, vapour of common salt, coal smoke ; from six copper-smelting 

 works, — sulphuric acid, sulphurous acid, coal smoke ; from six col- 

 lieries, six iron foundries, two soap-works, 8000 dwelling-houses, 

 — coal smoke; from the Sankey Brook and the heaps of alkali 

 waste, — sulphide of hydrogen. 



This is a formidable list, but the amounts of each may be calcu- 

 lated with a very near approach to accuracy, except the last item, 

 the sulphide of hydrogen, which varies Continually with the amount 

 of rain-fall, and with the temperature of the air. 



Having, then, collected the information as set forth under these 

 four heads, it became merely a question of figures to apply it to the 

 solution of the problem raised in the St. Helens law-suit. A list 

 was made out of the principal factories in the district capable of doing 

 injury to the plaintiff's land. Opposite these was set down the dis- 

 tance of each factory from the land and, in a parallel column, the 

 amount of acid vapour thrown up by each. On dividing the figures 

 in the second column by those in the first, numbers were obtained 

 which were proportioned to the share each one had contributed to 

 the total damage done by all to the plaintiff's land. 



