500 REPORT—1904. 
These observations, and the conclusions to which they have led, have a very 
direct: bearing on the flow of rocks. The recognition of the transformation from 
crystalline to amorphous through an intermediate mobile phase, for the first time 
supplies an explanation of why flow which has been started by stresses can cease 
while the disturbing stresses are still maintained. 
2. The Action of certain Gases on Glass in the Neighbourhood of Hot 
Metals. By G. T. Beivpy. 
In a former paper (‘ British Association Report, 1903’) the formation of halos of 
decomposed glass around pieces of metal placed on glass plates and heated in a 
muffle to which the products of combustion had access was described. Further 
experiments and observations have been made to ascertain (1) To what chemical 
agent is the decomposition of the glass due? and (2) What is the cause of the 
localisation of this decomposition in the immediate neighbourhood of the hot metal 
as shown in the formation of halos and images ? 
By passing various gases over heated glass slips on which pieces of metal foil 
were placed, it was found that the most active agents in the decomposition of the 
glass were sulphur dioxide, air, and water vapour. 
The decomposition products of the glass were ascertained to be sodium or 
potassium sulphate and silica. 
In the original experiments, in which the products of combustion had access 
to the muffle, the source of the SO, was the trace of sulphur compounds in the coal 
gas used for heating. The actual attack on the glass is made by sulphur trioxide 
formed by the oxidation of the SO,,. 
The dull white film frequently seen on the outside of tubes or other glass 
vessels which have been heated in a gas furnace or muflle is no doubt due to the 
decomposition of the glass by the combustion gases, 
The second question, as to the cause of the localisation of the decomposition, 
cannot be answered so conclusively as the first. The active agent being SO,, the 
suggestion naturally occurs that its formation from SO, and air is accelerated by 
the presence of the hot metal, which acts as a catalyte. 
The question was discussed whether in this case the combination of these gases 
takes place on the surface of the metal or whether it takes place to some extent in 
the surrounding atmosphere. The appearances suggest that the agent which 
caused the decomposition had been in the form of a detinite cloud of particles shot 
out from the metal surface rather than in the form of widely diffused molecules of 
SO, in a very large volume of air. While no traces of metal could be detected in 
the halos or images, it does not seem necessary to suppose that the particles thrown 
off by the metal must be either visible or ponderable in order that they may 
produce very powerful effects. 
It cannot be claimed that these observations give a final answer to the second 
question proposed ; but they certainly do not give a final negative to the sugges- 
tion that some part of the effect may be due to the slow disintegration of the 
metal. 
3. On the Formation of Salts in Solutions, especially amongst Tautomeric 
Compounds. By Professor J. W. Bruny. 
4, Methods of Investigating Alloys, illustrated from the Copper-Tin Series. 
By C. T, Heycock, /.A.S., and F. H. NEvitie, “2.8. 
