MATTER AND FORCE. 38$ 
electric current from wire to wire. Bubbles of gas rise 
immediately from each of them, and these are the two 
gases of which the water is composed. The oxygen is 
always liberated on the one wire, the hydrogen on the 
other. The gases may be collected either separately or 
mixed. I place upon my hand a soap bubble filled with the 
mixture of both gases. Applying a taper to the bubble, a 
loud explosion is heard. The atoms have rushed together 
with detonation, and without injury to my hand, and the 
water from which they were extracted is the result of. their 
reunion. 
One consequence of the rushing together of the atoms is 
the development of heat. What is this heat? Here are 
two ivory balls suspended from the same point of support by 
two short strings. I draw them thus apart and then liber- 
ate them. They clash together, but, by virtue of their elas- 
ticity, they quickly recoil, and a sharp vibratory rattle 
succeeds their collision. This experiment will enable you 
to figure to your mind a pair of clashing atoms. We have 
in the first place, a motion of the one atom toward the 
other a motion of translation, as it is usually called 
then a recoil, and afterward a motion of vibration. To 
this vibratory motion we give the name of heat. Thus, 
three things are to be kept before the mind first, the 
atoms themselves; secondly, the force with which they 
attract each other; and thirdly, the motion consequent 
upon the exertion of that force. This motion must be fig- 
ured first as a motion of translation, and then as a motion 
of vibration, to which latter we give the name of heat. For 
some time after the act of combination this motion is so 
violent as to prevent the molecules from coming together, 
the water being maintained in a state of vapor. But as the 
vapor cools, or in other words loses its motion, the mole- 
cules coalesce to form a liquid. 
And now we approach a new and wonderful display of 
force. As long as the substance remains in a liquid or 
vaporous condition, the play of this force is altogether 
masked and hidden. But as the heat is gradually with- 
drawn, the molecules prepare for new arrangements and 
combinations. Solid crystals of water are at length formed, 
to which we give the familiar name of ice. Looking at 
these beautiful edifices and their internal structure, the 
