556 THE POPULAR SCIENCE MONTHLY. 



A steam-engine consists of two principal parts, the boiler and the 

 engine proper, or motor. We suppose that with the boiler employed 

 at Tours we can use the common motors ; this is one of the advantages 

 possessed by the solar apparatus, viz., that it does not require a special 

 form of motor. At first the inventor employed for his demonstrations 

 a double-acting engine, without either condensation or detention of 

 steam, the cylinder of which had a capacity of one-third of a litre. 

 This engine performed eighty strokes per minute, with a steady press- 

 ure of one atmosphere ; it continued to work even under a slightly- 

 clouded sun. This was later superseded by a rotary engine, that is, 

 an engine with revolving cylinder, which avoids all transmission of 

 movement ; but the system is faulty. Yet this engine worked very 

 well, driving at high velocity a little pump for raising water ; the 

 pump, however, being of weak construction, became disabled. It is 

 a pity that the inventor has never measured the real work performed 

 by his engine, by means of a dynamometer. 



The solar reflector, being first of all a furnace using fuel that costs 

 nothing, is not only of use as a means of developing motive force, 

 but can also be employed for a multitude of purposes for instance, 

 distilling water to make it fit for drinking, concentrating and crystal- 

 lizing saline solutions, preparing alcohol, etc. Five litres of wine can 

 be distilled in a quarter of an hour by passing the vapor from the 

 apparatus into a still. The manufacture of alcohol from grain, sugar- 

 cane, or beet-root, would be equally easy. The steam generated by 

 this apparatus can also be employed for cooking fodder for cattle. 

 M. Mouchot has devised a form of small marmites, quite different 

 from his large steam-generator. These can be used by hunters for 

 preparing their meals, and explorers of great deserts will now have 

 something besides camel or buffalo chips for cooking their victuals. 



Many and varied are the uses of this curious invention. The aero- 

 naut can with its aid propel his air-ship. Hot-air motors and ammo- 

 nia engines will be benefited by the use of the solar receiver ; but it 

 is especially in tropical countries that it is destined to find immediate 

 employment, in driving the various kinds of machinery used in sugar 

 and cotton plantations, in distilling impure water to make it fit for 

 drinking, in crystallizing saline and saccharine solutions, in pumping 

 water of irrigation, in manufacturing ice by means of the Carre ma- 

 chine, etc. In those countries fuel is scarce, firewood is not abundant, 

 and coal, which has to be imported from a distance, often from the 

 mines of England, commands an exorbitant price. Already in south- 

 ern countries sea-salt is obtained purely by the action of solar heat. 

 In Chili and in Mauritius, salt-marshes are divided into compartments, 

 with walls and roof of glass, in order to promote evaporation ; so in 

 the famous nitre-beds of Iquique, on the coast of Peru, the salt might 

 be crystallized by solar heat alone. 



The cost of a solar apparatus of half a horse-power, like that 



