SCIENTIFIC SUMMARY. 
435 
nated in the total defeat of the phlogistists and the entire destruction of 
their theory. The issue of the next great chemical controversy, that 
between the dualistic theory of Berzelius and the substitution theory of 
Dumas, Laurent, and Gerhardt, was very different. Some historical writers 
argue as if here also the new doctrine had superseded the old ; but the 
speaker maintained as a more correct view of what really took place, that 
each theory underwent independent developments ; and, inasmuch as both 
were sound, though imperfect, this development has now brought them very 
nearly to the same point. He illustrated this statement by an examination 
. of the views of Berzelius as to the constitution of acetic and trichloracetic 
acids and the constitution of ternary compound, and showed how the diffi- 
culties involved in some of these cases were cleared up by the discovery 
of the multiquivalent character of the atoms of certain elements. Dr. 
Brown defined chemical constitution as the order in which the constituents 
are united in the compound, and pointed out that the study of chemical 
changes (combination and decomposition) cannot lead us to a knowledge of 
the relative position of the atoms. But such a knowledge is required before 
a real theory of chemistry can be attained, and a knowledge of the intimate 
structure of matter may be looked for from an examination of the physical 
properties of substances, and comparison of these with their chemical con- 
stitution. This, he maintained, is truly a branch of chemistry, and the 
greatest progress in it has been made by chemists, as may be proved by 
reference to the work of Faraday, of Graham, and of Andrews. By pur- 
suing this branch discoveries may be made which will lead to a hypo- 
thesis directly connecting chemistry with dynamics, and enabling us to 
apply mathematics directly to chemistry. The theory of chemistry will 
then be a particular case of the theory of dynamics. Such a result must be 
expected by all who believe in the progress of human knowledge, and in the 
consistency of nature. 
Crystallisation of Glass. — M. Peligot states (in u Bull, de la Soc. d’Encour- 
age. pour l’Industrie Nationale,” No. 5), that in clearing out the glass furnace 
of M. Chagot, at Bianzy, certain crystalline geodes were found, which had 
been formed during the cooling of the vitreous mass. Their composition is 
given under No. i., No. n. being the transparent glass from which these 
crystals had separated, and No. in. the glass in its normal condition: — 
i. 
it. 
III. 
Silica 
. 62-3 
61-8 
62-5 
Lime 
. 22-7 
21-5 
21-3 
Magnesia . 
. 8-4 
5-4 
5-6 
Oxide of iron . 
. 3-2 
3-0 
3-0 
Alumina . 
. 2-5 
2-1 
2-1 
Soda 
. 0-9 
6-2 
5-5 
100-0 
100-0 
100-0 
Hence it appears that devitrified or crystallised glass has undergone, not a 
mere physical change of structure, but an alteration in its chemical composi- 
tion. The increase of magnesia, and the decrease of soda, are remarkable. 
The form of the crystals approaches that of pyroxene; that is, an oblique 
but nearly right prism. 
ff2 
