Purificatiow of Water. 293 
upon water which is hardened from the presence of 
acids and salts is but limited, and other substances, such as 
pure silica, &c. (having a great affinity for them) are far 
more effective. 
About ten years ago I found quite accidentally a most 
valuable filtering medium in the refuse of boghead coal. It 
appears that this coal yields more gas than any other kind 
known ; but, instead of coke, it leaves a pure silica of a 
very spongy nature—closely amalgamated with about ten 
to fifteen per cent. of carbon. 3 
By means of a simple process of my own I convert this 
substance into solid cakes of such size and porosity as may 
suit the different purposes, and thus I get not only a very 
effective filtering agent in quality; but, in this form it 
assists me greatly to overcome mechanical difficulties. 
I have patented this material under the name of silicated 
carbon, by which it is weli known in England. Various 
Government establishments, amongst which the General 
Post-office, the hospitals, and the public drinking fountains 
have adopted it; in fact the latter troduced it to the public 
at large. 
A lawsuit relating to the Boghead coal called my atten- 
tion to it. The lessee of the mine denied it to be a coal, 
because it would not yield coke when distilled. A great 
sum of money being at stake, there were a great number of 
scientific men called upon to give evidence, and the battle 
became very fierce. Becoming interested in the feud 
between the various and differing members of the learned - 
faculty, I profited greatly by finding a new and valuable 
filtering medium in the form of such a spongy silica as I 
had not met with before. 
This silicated carbon has been highly valued by the pro- 
fession, and Drs. Letheby, Waller, Lewis, Odling, Buchanan, 
Lankester, Noad and others used to support me strongly 
whenever I needed their aid. 
But a very few days ago I read an abstract of an article 
which the well-known water analyst, Dr. Rivers (to whom 
I am personally unknown), wrote for the “ Popular Science 
Review,” in which he discriminates the merits of the various 
filters now used in England. It was very pleasing for me 
to find that amongst the three systems which he has proved 
to be reliable for what they profess to do, he mentioned 
my own silicated carbon. Of.the rest he seems to have 
formed but a very poor opinion. 
