642 Proceedings of the Royal Society of Edinburgh. [Sess. 
affected by minute traces of these materials, their presence may influence 
the shape of the temperature curve (fig. 4). Experiments upon this point 
will be shortly begun. 
The available data relating to the molecular structure of glass are very 
limited, and it is hoped that the property of conduction will afford a fresh 
starting-point for further work in this direction. 
I desire to express my indebtedness to the Managers of the Royal 
Institution for kindly allowing me to make the optical and softening point 
measurements at the Davy-Faraday Laboratory, and to acknowledge the 
help given me by my assistant, Mr Threadgold. 
{Issued separately October 12, 1908.) 
