218 ANNUAL OF SCIENTIFIC DISCOVERY. 



he has arrived at, since the outset of his experiments, which is well 

 worthy of attention. He says: Towards the close of 1853, my 

 attention was first directed to the deodorizing and disinfecting prop- 

 erties of charcoal ; and I was not long in discovering that the views 

 which had been previously entertained regarding the action of char- 

 coal were exceedingly erroneous ; for, instead of acting as an anti- 

 septic, and thereby retarding the decay of putrefying substances with 

 which it was in contact, as had been previously supposed, its action 

 was the very reverse of this. Charcoal, therefore, from the consid- 

 erable amount of condensed oxygen contained within its pores, 

 amounting to between nine and ten volumes (and which, it might 

 have been added, appears to be continually renewed of itself, unless 

 the pores be allowed to be filled with water, or the charcoal, in other 

 words, to become wet), not only absorbs, but rapidly oxidizes the 

 effluvia and miasmata emitted by decaying substances, and resolves 

 them into the simplest combinations they are capable of forming. 



All porous substances, such as platinum black, pumice-stone, etc., 

 possess the power of condensing gas within their pores. 



The charcoal air-filter consists of a layer of charcoal in coarse 

 powder, varying in size, according to circumstances, between a small 

 bean and a filbert. The charcoal is placed between two sheets of 

 wire gauze fixed in a frame, and can be readily applied to buildings, 

 to ships, to the air-shafts of sewers, to water-closets, to respirators, 

 and various other purposes. All the impurities in the air are absorbed 

 by the charcoal, so that a current of pure air alone passes through the 

 filter; and in this way pure air may be obtained from exceedingly 

 impure sources. It is plain that perforated zinc, or a framework of 

 coarse wire filled with larger pieces and a greater thickness of char- 

 coal, may be also employed, whenever the amount of effluvia evolved 

 is very considerable. 



Before the close of the year 1854, air-filters or charcoal ventilators 

 were fitted up both at the Mansion House and Guildhall. They are 

 each of them several feet in diameter, the layer of charcoal being 

 about one and a half inches in thickness. Although six years have 

 elapsed, the charcoal has never required to be renewed, owing to its 

 oxidating power being practically unlimited. Air-filters were soon 

 afterwards largely employed in private houses, in connection with 

 drains and water-closets particularly; and they were also very suc- 

 cessfully applied to the construction of respirators, many thousands of 

 which have ever since been annually manufactured. 



Mr. Rawlinson, during the last four years, has applied charcoal air- 

 filters to the ventilation of sewers on a large scale, near London, 

 at Swansea, and other places. The efficiency of the charcoal appears 

 never to diminish, if it is kept dry and its pores are not choked up by 

 dust. 



The expense of applying charcoal to the disinfection of the sewers 

 is by no means considerable, as the first outlay is all that is required. 

 The only precautions to be observed are, that while the filters shall be 

 sheltered from rain and moisture, free access shall be given to the air. 

 In conclusion I may state, that for the last six years I have strongly 

 recommended that charcoal air-filters should be applied to all house- 

 drains, sinks, and water-closets. 



