of removing mattei' from Solution in Water, 31 



points are in themselves remarkable in the results obtained by 

 this filtration through sand : — 



1st. That the filter continued increasing in efficacy even till 

 the conclusion of the experiment, i. e. for 376 hours, not having 

 lost any of its power when the experiment was terminated. 



2nd. That no weighable quantity of dissolved organic matter 

 was removed by the sand in this experiment ; but it must be 

 remembered that the quantity originally present was but small. 



3rd. Its power of removing soluble salts was considerable ; as 

 a maximum, 21 per cent, of the common salt being separated. 



Table VI. — Results of Charcoal Filtration. 



On comparing this experiment with the preceding, the follow- 

 ing points come out as showing the difference between the effects 

 of sand and charcoal as filtering media. 



1st. By the charcoal, speaking generally, a considerably larger 

 quantity of the total residue contained in the water was removed 

 than by the sand, their maximum results being respectively as 

 follows : — 



But, as might have been anticipated from the well-known 



