108 
will find in my general report to the Academy of Vienna, 
published by Gerold. 
“No eruption of a telluric nature can be the cause of a 
change in Linne, but a filling up of the crater by masses 
of mud or dust ; otherwise the shadow of the smoke, as in 
an ordinary eruption such as I observed at Vesuvius and 
at the Sartorin Islands, would not have escaped my 
observation.” 
“Brief Notes on the Laws of Physical Force,” by J. C. 
Dyer, Esq., V.P. 
The wide acceptance of the new doctrine of the conser- 
vation of physical energy, or force, has led me to submit a 
few remarks thereon. 
In the first place, let us keep in mind that there are five 
kinds of natural forces continually exerted by material 
bodies. Three of these are mechanical forces, and, as such, 
are measurable by the known laws of physics — viz., the 
force of gravity, of inertia, and of elasticity, each being co- 
extensive with, and inherent properties of all tangible 
bodies. The actual exertion of these, by their equal action 
and reaction, serves to sustain the positions and forms 
(whether in motion or at rest) of the entire material uni- 
verse ; and it is only by the observed action of such balanced 
forces that we are assured of the existence of material 
bodies. 
Many theories have been propounded to account for the 
presence of these several forces in matter ; yet no real light 
has been shed upon the questions involved in such inquiries 
beyond the fact that all these forces are found to be essen- 
tial forces of the bodies exerting them. The two first 
are directly as the quantity of matter, and the third or 
elastic force varying in degrees of action according to the 
condition of bodies as solids, liquids, gases, or vapours. I 
have elsewhere aimed to show that a pervading “calorific 
