156 
Proceedings of the Royal Society 
to be able to communicate before long to the Society the result of 
experiments in this direction. Meantime I wish to draw attention 
to the peculiar behaviour of paraffin under pressure, as brought out 
by some experiments of Bunsen’s, undertaken fora different purpose.* 
His results are shown graphically in the accompanying diagram. 
The curved lines represent the variation of the melting-point with 
pressure. Pressure is measured upwards, and temperature hori- 
zontally. The least curved line sloping up is that of spermaceti. 
The markedly curved line is that of paraffin. The line sloping down 
is that of water. The direction of slope shows that the substance 
expands in the act of freezing, as its melting-point is lowered by 
pressure. If the paraffin curve continues to bend at the same rate 
as the pressure is increased, beyond the point reached in Bunsen’s 
experiments, its tangent line will become horizontal, and the curve 
will be concave to the temperature axis. That is to say, paraffin 
under these pressures will behave as water does, i.e ., will expand in 
the act of freezing. The temperature corresponding to the point 
* Pogg. Ann,, lxxxi., Dec. 1850. 
Pressure for water curve 
