required. The experiments on various substances were repeated many
times. The mean results for those in which we are immediately
interested are given in Table I., next column.

Comparison with later determinations have established their
substantial accuracy. The general conclusion arrived at is thus
stated:

"As a rule there is an equality between the heat disengaged or
absorbed in the acts, respectively, of chemical combination or
decomposition of the same elements, so that the heat evolved during
the combination of two simple or com-pound substances is equal to the
heat absorbed at the time of their chemical segregation."

TABLE I.--SUBSTANCES ENTERING INTO THE COMPOSITION OF FUEL.

-----------------------+-------------+-----------+-------------------+
| | Heat evolved in |
| Symbol and Atomic |the Combustion of |
| Weight. | 1 lb. of Fuel. |
+------------+------------+--------+----------+
| | | |In Pounds |
| | | In | of Water |
| | |British |Evaporated|
| Before | After |Thermal | from and |
| Combustion | Combustion | Units. | at 212°. |
+------------+------------+--------+----------+
Hydrogen burned | H 1 | H2O 18 | 62,032 | 64.21 |
in oxygen. | | | | |
-----------------------+------------+------------+--------+----------+