In order to utilize the steam as a means of heating, it is necessary to condense it, that is to say, to cause it to pass from the gaseous to a liquid state. This conversion disengages as much heat as the passage from the liquid to the gaseous state had absorbed. It results from this that if we could condense the steam that is given off by a liquid that we are vaporizing, in contact with another liquid that it is also a question of vaporizing, we should utilize all the heat contained in the steam that was being given off from the first. This object can be practically attained by two means, viz., by (1) putting the disengaged steam in contact with the sides of a vessel that contains a liquid colder than the one that produced it; (2) by raising the temperature and pressure of the disengaged steam in order to condense it in contact with the sides of the vessel which contains the very liquid that has produced it. The first of these means is realized in the apparatus called multiple acting, that are at present so generally employed in sugar works. The second means, which permits of a greater saving in fuel being made than the other does, is realized by compressing the disengaged steam. This compression, which raises the temperature and pressure of the steam, permits of condensing the latter in contact with the vessel wherein it has been produced. By such condensation we continuously restore to the liquid which is being vaporized the heat of the steam which it gives off. This solution of the question, which has been partially seen at different epochs, has but recently made its way into the industries. It is being operated at present with complete success at the salt works of France and Switzerland, at those of Austria and Prussia, in the sugar of milk factories of France and Switzerland, and, finally, in 1882, the first application of it in the sugar industry was made at Pohrlitz, in Moravia. The saving of fuel that has been made in these different applications has always been great. We shall now, for the sake of explaining the system, give a brief description of the apparatus as used at the Pohrlitz sugar works mentioned above. These works treat 255 tons of beets per 24 hours, and obtain 4,000 hectoliters of juice, which is reduced to about 1,000 hectoliters of sirup. Up to the present, the concentration has been effected in a double acting apparatus partly supplied by exhaust steam from the motive engines and partly by steam coming directly from the generators. In order to diminish the consumption of direct steam, these sugar works put in a Weibel-Piccard apparatus designed to concentrate only a third of their juice, or about 1,350 hectoliters per day.