238 Progress of Invention. 



until the pressure 'within it very slightly exceeds that of the ex- 

 ternal atmosphere ; there will then be little tendency to leakage, 

 but if a leak should exist, it will be readily detected and stopped. 

 When the tank arrives at its destination, it is to be put in connec- 

 tion with the receptacle to be emptied, and at the same time with a 

 small quantity of water properly situated for the purpose. The 

 ammonia is, of course, instantly condensed, a vacuum is formed, 

 and the tank is filled by atmospheric pressure, The water used for 

 condensing the ammonia may be transferred to the boiler already 

 mentioned, so that nothing will be wasted. 



Regulation or Temperature by means of a Self- Acting Ther- 

 mometer, — A thermometer intended for this purpose has been in- 

 vented by General Morin. It is simple and effective ; it would 

 seem to be applicable to the prevention of either too high or too 

 low a temperature ; and even, by a further development of the 

 principle, to be capable of lowering the temperature by a ventilating 

 apparatus it might set in action; or raising it, by producing a 

 required modification in the supply of heat. 



To construct this thermometer, a piece of platinum foil is her- 

 metically fixed in the bulb of the instrument, and another in the 

 stem just at the point to which the mercury will reach, when the 

 temperature is exactly what it should be. These slips of platinum 

 are to be connected with the poles of a galvanic battery, the helix 

 of an electro-magnet forming part of the circuit. When the mer- 

 cury sinks too low in the stem of the thermometer, battery connec- 

 tion is broken, the -electro-magnet loses its excitement, and an 

 armature, which it had previously continued to support, immedi- 

 ately falls. This completes an electric circuit, setting in motion a 

 current which throws a loud alarm into action, and continues to 

 sound its bell until the proper temperature has been reproduced. 



A New Caloric Engine. — A new kind of caloric engine has 

 been lately invented in Germany. Its chief peculiarity consists in 

 air being forced for the support of combustion into an air-tight 

 furnace, within which is placed a fireplace of refractory clay. The 

 products of combustion, mixed with a little steam, which is in- 

 tended principally to furnish a kind of lubrication for the reciproca- 

 ting portions in contact with it, give motion to two pistons of pecu- 

 liar construction, after which they escape into the atmosphere. 

 The combustion produced in this way is very energetic, being, it is 

 said, sufficient, when a pressure of about four atmospheres is em- 

 ployed, to fuse malleable iron. Increase of velocity produces an 

 immediate increase in the intensity of combustion ; and this increase 

 of intensity reacts at once on the velocity, so that there is a great 

 tendency in this engine to a very rapid motion — which in many 

 cases is a great advantage. It is asserted that, with this arrange- 

 ment, a much greater calorific effect is obtained from a given 

 amount of fuel than in the ordinary way. 



Miscellaneous. — Improved Bunsen Battery. — The vapours 

 evolved by the ordinary Bunsen battery are very prejudicial to 

 health. M. Emile Duchemin gets rid of them without a loss of 



