vapor;
the quantity and weight of steam expended at each oscillation by one of
Newcomen's engines of known dimensions; the quantity of cold water that
must be injected into the cylinder to give a certain force to the
piston's descending oscillation; and finally the elasticity of steam at
various temperatures.

Here was enough to occupy the life of a laborious physicist, yet Watt
found means to conduct all these numerous and difficult researches to a
good termination, without the work of the shop suffering thereby. Dr.
Cleland wished, not long since, to take me to the house, near the port
of Glasgow, whither our associate[57] retired, on quitting his tools, to
become an experimenter. It was razed to the ground! Our anger was keen
but of short duration. Within the area still visible of the foundations
ten or twelve vigorous workmen appeared to be occupied in sanctifying
the cradle of modern steam-engines; they were hammering with redoubled
blows various portions of boilers, the united dimensions of which
certainly equalled those of the humble dwelling that had disappeared
there. On such a spot, and under such circumstances, the most elegant
mansion, the most sumptuous monument, the finest statue, would have
awakened less reflection than those colossal boilers.

If the properties of steam are present to your mind, you will perceive
at a glance that the economic working of Newcomen's engine seems to
require two irreconcilable conditions. When the piston descends, the
cylinder is required to be cold, otherwise it meets some steam there,
still very elastic, which retards the operation very much, and
diminishes the effect of the external atmosphere. Then, when steam at
the temperature of 100 deg. flows into the same cylinder and finds it cold,
the steam restores its heat by becoming partially fluid, and until the
cylinder has regained the temperature of 100 deg. its elasticity will be
found considerably attenuated; thence will ensue slowness of motion, for
the counterpoise will not raise the piston until there is sufficient
spring contained in the cylinder to counterbalance the action of the
atmosphere; thence there will also arise an increase of expense.

No doubt will remain on the immense importance of this economical
observation, when I shall have stated that the Glasgow model at each
oscillation expended a volume of steam several times larger than that of
the cylinder. The expense of steam, or, what comes to the same t