of removing Matter from Solution in Water, 



33 



water collected at Kingston on the 8th of October, 1855, cow- 

 dung and garden mould were added, in the proportion of 4 oz. of 

 solid cow-dung (without straw) and 4 oz. of garden mould to 2 

 gallons of the water ; the whole was allowed to digest for a week, 

 being frequently shaken during this period ; it was then allowed 

 to settle for twelve hours, and the supernatant fetid fluid poured 

 off and submitted to examination. It was found to contain in 

 the gallon- 

 Total residue . . . 71*772 grs. 

 Organic matter . . 29-308 ... 

 Mineral matter . . 42*468 ... 



And the results obtained by filtration respectively»through sand 

 and charcoal are contained in the following Tables : — 



Table VII. — Action of Vegetable Charcoal on artificially 

 impure Water. 



It must be borne in mind that these two experiments, being 

 made only on the small scale in the laboratory, though strictly 

 comparable with each other, do not admit of comparison with any 

 of the others ; they serve only to demonstrate how far greater is 

 the power possessed by charcoal of removing organic matters 

 from solution than that of sand, though the differente in their 

 action on soluble inorganic salts is less marked. 



Another point of distinction between the effects of charcoal 

 and sand upon the Thames water at Kingston was this — that 

 whereas the efficacy of the sand-filter continued increasing even 

 up to the conclusion of the experiment, the amount of impurity 

 separated by the charcoal arrived in all cases at a maximum after 

 a certain number of hours, and then began to decrease, as will 

 be more perspicuously shown by the following Table : — 



Phil. Mag, S. 4. Vol. 12. No. 76. July 1856. D 



