o-l Mr. II. Mcdlock on the Reciprucal Action uf Metals 



from the surface-drainage of richly manured and highly cultivated 

 lands, and, more objectionable still, from the sewage and refuse 

 of towns. The complex organic matters derived from these 

 several sources are by certain influences, and in course of time, 

 resolved into more simple compounds which are comparatively 

 innocuous. ThaTnes water, as is well known, if allowed to stand 

 in an open vessel for a few days in warm weather, acquires a 

 very offensive odour, arising from the decomposition of the 

 animal and vegetable matter held in solution. This water, not- 

 withstanding, is considered by maritime authorities to be the 

 very best for the use of ships^ companies. On board-ship the 

 water is stored in wooden casks, which are stowed low down 

 in the hold. During the first week or fortnight, according to 

 the temperature of the atmosphere, the water undergoes a kind 

 of fermentation, evolves a quantity of gas possessing a most 

 i>ffeusive odour, and deposits a co]nous brown sediment. The 

 water gradually ceases to smell offensively, becomes bright and 

 sparkling, and will then keep fresh and sweet for an indefinite 

 length of time. In other words, it loses by a natural process of 

 decay, the whole of its putrescent impurities. In our vessels of war 

 and most of our large steamers, tanks of iron have been substituted 

 for casks of wood for storing the water necessary for the use of the 

 ])asscngers and ships' company. I am informed that in iron tanks 

 Thames water evolves no offensive gases, but becomes pure much 

 quicker than when stored in wood, and deposits a more copious 

 brown sediment which turns red on exposure to the air. The 

 gases produced in the tightly-bunged wooden casks are said 

 to be slightly luminous in the dark, and to explode when a 

 lighted candle is incautiously placed near the bung-hole when 

 the bung is removed. 



The gases arising from the decomposition of the organic mat- 

 ter contained in Thames water, possess an odour /«?• more offensive 

 than even that of sulphuretted hydrogen, of phosphuretted hy- 

 drogen, or of sulphide of ammonium. 



The well-known influence of the gaseous exhalations from 

 stagnant waters in producing malarious diseases, renders it highly 

 probable that the gaseous products of the decomposition of 

 organic matter possess poisonous qualities, and the true cha- 

 racter and composition of which have hitherto eluded the u)ost 

 delicate chemical tests. 



Having discovered that when the Amsterdam water was allowed 

 to remain in contact with a large surface of iron for forty-eight 

 hours, the whole of its organic matter was precipitated, together 

 with part of the mineral constituents, I thought it desirable to 

 study the action of iron upon the organic matters contained in 

 Thames water, since it promised to furnish a means of removing 



