2 4 z THE POPULAR SCIENCE MONTHLY. 



This is a question which experience alone can decide. Doubt- 

 less the larger the area of screened opening, the more effective 

 the filtration. For a book-case with glazed front, probably the 

 whole of the back might be made of flannel loosely fixed over the 

 necessary skeleton framework. For a cupboard or closet, every 

 panel should be replaced by a screen. If the closet have a win- 

 dow, all crevices and joints in the window should be pasted up to 

 exclude the soot, otherwise the wind from, the outside, or the fires 

 of the house from the inside, will force the air soot through. On 

 the other hand, it is probably true that, given very perfect fitting 

 and workmanship, aided by the interposition of velvet, as here- 

 after described, where the edges of the doors come in contact 

 with their frame, a much smaller area of filter, perhaps even a 

 simple tube, filled with cotton-wool, may prove to be efficient. 

 These, however, are points on which further experience is needed, 

 and which may, ere long, be settled by experiment. 



Where shall we place our screen ? This is a question which 

 admits of a variety of answers, and gives scope for endless inge- 

 nuity. In anything which is being newly made, such as the cup- 

 boards and closets of a new house, or in new furniture, we are 

 masters of the situation. In many of them we may substitute at 

 the back our filtering texture for wooden boards, and perhaps 

 even save expense thereby. In closets we may replace the panels 

 of the door by filtering texture, guarding the closets, if necessary, 

 against thieves by wire netting or iron bars fixed on the inner 

 side. As a rule, chests of drawers may have the filter over the 

 whole surface at the back, care being taken that the back of each 

 drawer falls half an inch short of the top of the drawer, to allow 

 free entrance of air from the screen. In one set of drawers, so 

 placed that I could not get at the back, the difficulty was got over 

 in this way : In the front of each drawer a series of twenty holes, 

 of an inch diameter, was made for admission of air. The filter, 

 on a frame, was fixed on the inner surface of the front of the 

 drawer, so that the material should stand half an inch away from 

 the holes. A somewhat similar plan was adopted in a bureau. 

 About twenty large holes, two inches in diameter, were cut in the 

 wood-work at the back, some of the holes being opposite pigeon- 

 holes. Then the whole was covered with bunting, on a frame so 

 arranged that the bunting was fully half or two thirds of an inch 

 away from the wood. Another method has been adopted at the 

 Yorkshire College for some of the cases. The filter was applied at 

 the roof, somewhat after the fashion of a weaving-shed roof, the 

 vertical face being filled in by the screen. Again, Mr. Branson has 

 provided a roof filter for a case of scientific instruments, by placing 

 the screen in the roof of the case, and protecting it by a false roof 

 two inches above it, to prevent its being choked by falling dust. 



