282 METHODS OF VENTILATION. 



proportions which appear, by oft-repeated trials, to be most 

 beneficial. 



7. We could describe several other systems of ventilation, 

 by what we have called the compound method, which have a 

 greater number of wheels and rachets, and other kinds of ma- 

 chinery about them, but which possess no advantage over either 

 of the methods we have described. One system, in particular, 

 has received some countenance, which consists in opening by 

 the aid of a spring instead of the toothed rod, as shown in Fig. 56. 

 We have managed various houses ventilated by this method, but 

 we must say that it worked badly, although much care had been 

 taken to have the machinery properly fitted up ; for instance, 

 where the springs are of unequal strength, and by constant 

 use they very soon become so, you will find a very great irreg- 

 ularity in the airing of the house, some of them requiring to be 

 opened nearly full length, before the others will open a few 

 inches. Again, if some of the sashes be stiff to open, those 

 that are not so will open freely, while the ones that are hard to 

 move will not open at all. This has frequently caused us much 

 annoyance. It can never occur with the toothed wheel, as an 

 equal force is exerted on each ventilator or sash, and every sash 

 is opened to a regular distance. But if any of the sashes be 

 stiff to open, then the whole power applied is directed upon 

 them alone, until the whole move together. The only supposed 

 advantage of the springs is, that they do the work silently, 

 whereas a little noise is made by the rachet-wheels, a matter, 

 in most cases, of so trifling importance, as to be unworthy of 

 consideration ; but, as drowning men catch at straws, so the most 

 insignificant circumstance is eagerly seized, and magnified into 

 momentous import, by would-be inventors, for the purpose of 

 palming off their so-called invention upon the community, and 

 sustaining its sinking reputation. The less machinery there is 

 about a hot-house, the better ; and that system which does its 

 work in the most efficient manner, with the smallest amount of 

 labor, and is least likely to get out of order, is decidedly to be 

 preferred. This is a commendation which cannot be justly 

 given to some late inventions ; and, without wishing to throw 



