876 REPORT— 1893. 



that a great advance has heen made in the last year or two in the ventilation of 

 large public and private buildings, to which class of buildings he will more 

 particularly confine himself, and that if only a sufficient — by no means extrava- 

 gant — amount of money is provided for it, some really definite results can be 

 guaranteed. 



It will not be necessary here to give an elaborate statement why it is necessary 

 to provide for a proper supply of heat and pure air to our schools and public 

 buildings ; this has to some extent been done in the paper itself, which has been 

 printed for circulation, and which may be referred to ; but the author would like, 

 to point out at once that, in his opinion, no scheme of ventilation is complete 

 which does not provide at the same time for the warming of the incoming air. 



The various methods of ventUation may be grouped under two heads, viz., 

 ventilation by natural means and ventilation by artificial or mechanical means. 



Not much need be said here about natural ventilation, as it is now almost 

 generally admitted that it is not suited for the ventilation of large public or private 

 buildings, and in the future remarks attention will only be paid to mechanical 

 ventilation, which will be subdivided again into mechanical ventilation by extrac- 

 tion (Vacuum system) and mechanical ventilation by impulsion (Plenum sj'stem). 



The author's firm has had the good fortune to carry out a large number of 

 ventilation schemes in various parts of the country, in which either the one or the 

 other system or combinations of the two have been employed, some of which have 

 been described in the paper at considerable length with the aid of eight diagrams ; 

 and he has come to the conclusion that, where the Plenum system can be employed, 

 it is the best and most reliable of all the schemes of ventilation. It is assumed 

 here that the scheme is well designed, well carried out, and M-ell superintended, 

 as no scheme whatsoever has a fair chance if these conditions have not been 

 complied with. 



One of the chief drawbacks of the Vacuum system is the uncertainty as to the 

 purity of the incoming air, which will be drawn from that place that offers 

 the least resistance to the passage of the air, and if badly constructed drains and 

 sewers are near it may come from these. 



Various objections have been raised against the Plenum system, and it is said 

 to have been a failure in several cases. Of course the author cannot attempt to 

 deal with installations put up by other gentlemen, but he would most emphatically 

 say that his experience, which he has given in the paper, does not bear out those 

 contentions, which not unfrequently have proceeded from quarters interested in 

 ventilation by natural means. 



All the objections cannot be considered here, but one or two of the more 

 prominent ones will be dealt with shortly in the following remarks : — 



1. As to breakdowns of the machinery. 



It has been stated that if the engine breaks down no fresh air can be supplied 

 till it is repaired. 



In this respect the system stands on the same basis as all other so-called 

 natural or mechanical schemes of ventilation, with this advantage, perhaps, that 

 an accident to the machinery is at once noticed, and can be remedied without 

 delay, whereas a breakdown in a patent cowl or some such appliance may not be 

 noticed for a considerable time, as nobody attends to it. 



It would, however, not be true to say that during a breakdown no fresh air at 

 all will be supplied : this would only be the case during the warm weather, and 

 then the openings of the windows will soon remedy it. During a breakdown in 

 winter the hot air will still, to some extent, ventilate the rooms till the repairs are 

 complete. This would be the condition of things in cases where no duplicate 

 power is provided ; but where this has been done, either by an extraction-tower, as 

 at Nottingham, or a fan in the roof driven by an electric motor or by a duplicate 

 engine at the air inlet, then no inconvenience at all will be felt during repairs ; 

 and though this course will prove somewhat more expensive at first, yet in the long 

 run it will be the cheapest, and should be adopted in all cases where a temporarily 

 reduced supply of fresh air entails hardship or danger to life. If this is done, then 

 it may safely be asserted that the Plenum system is the most reliable system of 

 Tentilation. 



