a solution of hydrate of soda, having a high boiling point, and if the steam, after having done the work of propelling the pistons of an engine, is conducted with a reduced pressure and a reduced temperature into the solution, the latter, absorbing the steam, is diluted with simultaneous development of heat, which produces fresh steam in the boiler.  This process will be made clearer by referring to the following table of the boiling points of soda solutions of different degrees of concentration, and by the description of an experiment conducted by Professor Riedler with a double cylinder engine and tubular boiler as shown in Fig. 2: 

+---------------------+------------------+-------------

---------
|                     | Boiling point in | Steam pressure above
|  Solution of soda.  |   Centigrades.   | atmospheric pressure
|                     |                  |   in atmospheres.
+---------------------+------------------+------------------

----
|100 NaO HO +  10 H2O | 256   deg.  C.    |     40    atm.
|      "    +  20  "  | 220.5    "       |     21     "
|      "    +  30  "  | 200      "       |     15     "
|      "    +  40  "  | 185.5    "       |     10.2   "
|      "    +  50  "  | 174.5    "       |      7.7   "
|      "    +  60  "  | 166      "       |      6.1   "
|      "    +  70  "  | 159.5    "       |      5.1   "
|      "    +  80  "  | 154      "       |      4.2   "
|      "    +  90  "  | 149      "       |      3.6   "
|      "    + 100  "  | 144      "       |      3.0   "
|      "    + 120  "  | 136      "       |      2.2   "
|      "    + 140  "  | 130      "       |      1.6   "
|      "    + 200  "  | 120      "       |      0.95  "
|      "    + 300  "  | 110.3    "       |      0.4   "
|      "    + 400  "  | 107      "       |      0.3   "
+---------------------+------------------+------------------

----

Experiment No. 15.[3]—­The boiler of the engine, Fig. 2, was filled with 231 kilogs. water of two atmospheres pressure and a temperature of about 135 deg.  Cent.; the soda vessel with 544 kilogs. of soda lye of 22.9 per cent. water and a temperature of 200 deg.  Cent., its boiling point being about 218 deg.  Cent.  The engine overcame the frictional resistance produced by a brake.  At starting the temperature of both liquids had become nearly equal, viz., about 153 deg.  Cent.  The temperature of the soda lye could therefore be raised by 47 deg.  Cent, before boiling took place, but, as dilution, consequent upon absorption of steam would take place, a boiling point could only be reached less than 218 deg.  Cent., but more than 153 deg.  Cent.  The engine was then set in motion at 100 revolutions per minute.  The steam passing through the engine reached the soda vessel with a temperature of 100 deg.  Cent.; the temperature of the soda lye began to rise almost immediately, but at the same time the steam boiler losing steam above, and not being influenced as quickly by the increased heat below,