150 Scientific Proceedings, Royal Dublin Society. 
that the increased kinetic energy of the outside aqueous molecules ~ 
at a higher temperature (and lower humidity) tends by increased 
bombardment to break up the more readily the cohesion of the 
groups of molecules within the substance of the hair ? 
Here we may remark upon an exceedingly interesting 
discussion raised by an anonymous correspondent in the Monthly 
Weather Review some years ago.1 Among other questions he 
submitted the following :—“ Is there any clear explanation why 
increasing the temperature of a space increases the capacity of 
that space for vapor? If I understand correctly, a space becomes 
saturated when the vapor-pressure becomes such that for every 
molecule of water forced into it from the evaporating surface one 
is forced out. When this equilibrium is attained, would it not 
seem that raising the temperature of the vapor in the space would, 
by causing an increase in the vibration of the vapor molecules, 
cause a greater expansive force, and thus prevent rather than 
allow more vapor to passin? Of course experiment proves that 
more will pass in and can exist in the vapor state when the 
temperature is raised, but is there any explanation for mira 
In his answer to this question the editor of the Jonthly 
Weather Review wrote as follows :— 
« Any satisfactory explanation of the fact that the capacity of 
space for vapor increases with the temperature of the space, or, 
what is the same thing, the temperature of the vapor, must 
depend upon our knowledge of the nature of heat and molecules. 
According to the commonly accepted mechanical theory of heat 
and the kinetic theory of gases, the heat contained within a mass 
of vapor is simply the sum-total of the kinetic energy of the 
rapidly moving molecules of vapour. The molecules of a gas are 
supposed to be far apart, relative to their own size ; but by moving 
rapidly, by rebounding against each other and against the 
boundary of the enclosure, they occupy or dominate a large 
volume. ‘T’o increase the temperature of this enclosure is to 
increase the velocity of these molecules, and therefore the number 
of impacts and reflections that occur per second. 
“ By increasing the velocity and therefore the kinetic energy 
of the molecules, we also increase the momentum with which they 
1 For September, 1902. 
