1878.] Putrescent Organic Matter in Potable Water. 259 



iron, and on the bottom of which meat had been placed, the latter was 

 still in a perfectly fresh and hard condition. 



This result encouraged me to try in a similar way the action of 

 spongy iron upon hay infusion. The hay, steeped in water, was heated 

 for two days to about 35° C. The infusion then showed, under the 

 microscope, an abundance of organic life. I could not obviously test 

 the action of spongy iron upon this infusion, in the manner described 

 in my last paper, namely, by passing it continuously for weeks 

 through a vessel containing spongy iron and meat. However, I be- 

 lieve the result will be considered equally conclusive as to the absence 

 of any putrefactive agents in hay infusion after filtration through spongy 

 iron, should the meat remain fresh on being immersed in the filtered 

 liquid for several weeks. 



The following arrangement was adopted : — 



A large vessel was filled with the ordinary filtering materials em- 

 ployed in spongy iron filters, namely, commencing at the bottom, with 

 gravel, sand, pyrolusite, and spongy iron. The three first materials 

 were introduced to prevent the filtered solution containing any iron. 

 The vessel was provided with a neck at the bottom, and a volume of 

 the hay infusion, equal to the bulk of spongy iron in the filter, was 

 passed through it every 45 minutes. 



Into the neck of the vessel I fixed some tin tubing by means of an 

 india-rubber stopper. The tubing was connected with six tins, or 

 cylindrical vessels of tin-plate, holding about 500 cub. centims. each. 

 After placing a piece of fresh meat in each tin, a lid was soldered on 

 air-tight. The tubing was so arranged, that the inlet tube passed to 

 the bottom of each tin, an exit tube carrying the water off from the 

 top. By first pressing the tubing together, and then cutting it, all the 

 tins could be readily separated without exposure to air. Each tin was 

 provided on the top with a short piece of tubing, to serve later on for 

 the escape of steam. 



In order to wash the apparatus and materials, I passed, in the first 

 instance, water of the New River Company continuously through them 

 for 24 hours. The tins and contents were then immersed for two hours 

 in boiling water to destroy any putrefactive germs adhering to the 

 meat. After closing the tubing, which served during boiling for the 

 escape of steam, the tins were cooled, and then the filtration of New 

 River water continued for two more hours. 



The last two tins, which, it will be understood, contained filtered 

 water and meat, were now detached, and into one of them I passed 

 100 cub. centims. of filtered air, after connecting under alcohol with a 

 glass tube, 6 feet long, containing compressed cotton wool, through 

 which the air was forced. These two tins were kept for comparison 

 with those in which the meat was to remain in contact with filtered 

 hay infusion. The infusion was passed for six hours through the 



