as connected with the Theory of Substitutions. 347 
the discussions connected with the theory of substitutions, under 
the very circumstances contemplated, has its electro-chemical 
relations changed. 
More than two years ago I brought before the British Associa- 
tion some of the facts. 'They were subsequently published in 
the Philosophical Magazine in a memoir on “ 'Tithonized Chlo- 
rine.”* 'The connexion of these experiments with the discussion 
between the theory of substitutions and the electro-chemical theory 
is obvious. 
Very recently M. Berzelius has published an important paper 
on the allotropism of simple bodies, the object of which is to 
point out that many of those bodies can assume different qualities 
by being subjected to certain modes of treatment. Thus carbon 
furnishes three forms—charcoal, plumbago, and diamond. 
To acertain extent these views coincide with those which 
have offered themselves to me from the study of the properties of 
chlorine. They are not however altogether the same. M. Ber- 
zelius infers that elementary bodies can, as has been said, assume 
under varying circumstances different qualities. The idea which 
it is attempted to communicate in this memoir is simply this,— 
that a given substance, such as chlorine, can pass from a state of 
high activity, in which it possesses all its well known properties, 
to a state of complete inactivity, in which even its most energetic 
affinities disappear. And, that between these extremes there 
are innumerable intermediate points. Between the two views 
there is therefore this essential difference,—from the former, it 
does not appear what the nature of the newly assumed properties 
may be; from the latter, they must obviously be of the same 
character, and differ only in intensity or degree—diminishing 
from stage to stage until complete inactivity results. 
In the case of chlorine the same activity which is communi- 
cated by the indigo rays can also be communicated by a high 
temperature, or by the action of platina. 'The term “ tithonized 
chlorine,” which I formerly used, is therefore too restricted, and, 
indeed, in this view of the case improper. The simple appella- 
tions—active and passive, are perhaps the best, and I shall there- 
fore employ them. 
* London, Edinburgh, and Dublin Philosophical Mag., July, 1844. 
