308 Professor Hosking on Ventilation. 



The out-door ventilation of large towns may be taken to be more 

 complete above the tops of the houses and of their chimneys than it 

 is, or, perhaps, can be among and about the houses. The processes 

 of nature are there not only unchecked, but are in fact aided by the 

 heat thrown up by the chimneys into the upper air, and impurities 

 which can be passed off by chimney flues, will be more certainly 

 and more effectually removed and changed by Nature's chemistry 

 than if they are kept down to fester under foot and to exhale in our 

 streets and about our doors and windows. 



At this time every endeavour is made to provide for removing 

 from our dwellings all excrementitious matter, and all soluble refuse, 

 by drains into sewers, and so by the sewers to some outfall for dis- 

 charge. The drain necessarily falls towards the sewer, and the 

 sewer again to its outfall, and the sullage or soil drainage being 

 rendered liquid thus passes in the usual course. But the usages 

 and the necessities of civilized life cause a large proportion of the 

 liquid refuse from dwelling-houses to pass off in a heated state, or 

 to be followed by hot water arising from culinary processes, and 

 from washing in all its varieties. The heat so entering the drains 

 causes the evolution of fetid and noxious gases from the matters 

 which go with, or have gone before, the hot water ; and with these 

 gases house-drains almost always, and sewers commonly, stand 

 charged. They are light fluids and do not go down with the heavy 

 liquid matters from which they have been evolved, but they seek to 

 rise, and constantly do rise in almost every house through imper* 

 fections or derangements of the flaps and traps which are intended 

 to keep them down, but which only, when they do act, compel some 

 of the foul air to enter the sewers, and there to seek outlet to the 

 upper air which they find by the gulley gratings in the streets. 



It can hardly be said perhaps that too much attention has been 

 given of late to the scour of sewers by water ; but it is most certain 

 that too little attention has been given to the considerations last 

 stated, for nothing has been done to relieve the drains and sewers 

 of their worst offence. The evolution of foul and noxious gases in 

 the drains is certainly not prevented by scouring the sewers. In 

 the meantime the poison exists under foot, and exudes at every preg- 

 nable point within and about our houses, and it rises at every grat- 

 ing in our streets, though the senses may become dull to them by 

 constant suffering. 



Now this is an evil which can be greatly ameliorated, if it cannot 

 indeed be wholly cured ; but it is by a process that, to be effective, 

 must be general, and, therefore, it must be added, compulsory. The 

 process is of familiar application in the ventilation of mines, and 

 particularly of coal mines. An up-cast shaft containing a common 

 chimney flue carried up at the back of every house, and connected 

 with the house-drains at their highest level, would give vent to the 

 foul air in the drains, and discharge it into the upper air. The 



