180 Foreign Literature and Science. 



the outside. Some facts known to the author were at vari- 

 ance with this hypothesis : and he found upon trial, that when 

 single rods were made to approach a flame, the latter was al- 

 ways inflected, on all sides, from the rod, as if repelled by it, 

 and that this effect was independent of the conducting power 

 of the rod, whether good or bad. The amount of inflection 

 or repulsion, was directly as the mass and inversely as the 

 distance from the flame. It was not diminished by increas- 

 ing the temperature of the rod, even to such a degree as to 

 render it scarcely possible for it to abstract any of the calo- 

 ric. In fact, when two flames are made to approach each 

 other, there is a mutual repulsion, although their proximity 

 increases the temperature of each instead of diminishing it. 



" From these principles," says the author, " the theory of 

 the safety lamp is easily deduced. A metallic wire, exerting, 

 according to its diameter and its own nature a constant 

 repulsion upon flame, it is evident that two parallel wires, so 

 near each other as not to exceed the distance of twice the ra- 

 dius of the sphere of repulsion, will not permit a flame to in- 

 sinuate itself between them, unless it be impelled by a force 

 superior to the intensity of repulsion. If to these two wires 

 others be added, a tissue is formed impenetrable to flame, es- 

 pecially when the conducting power of the wires adds its in- 

 fluence to that of the repulsion.' 1 



The author conceives, that, from the views above stated, 

 the number of cross or horizontal wires in the Davy lamp, is 

 unnecessarily large, and that by rejecting all of these except- 

 ing a number sufficient to secure the firmness of the tissue, 

 the lamp would afford as great a security as at present, and 

 at the same time diffuse a much greater light. This opinion 

 he has verified by actual experiment. 



Bibliotheque Universelle de Geneva, Mars, 1827. 



33. Power of Steam. — The following laws of steam were 

 announced by M. Morin, in an interesting course of Lectures 

 at Geneva, attended by philosophers as well as artists. 



First Law. — Whatever may be the temperature and press- 

 ure under which the steam is produced, the same quantity 

 of heat must be employed to produce the same weight of 

 steam ; and as the quantity of heat developed is proportion- 

 ed to the quantity of fuel, it is obvious that a given weight of 

 steam, a kilograme, for example, will always cost the same 

 price, whether it be produced at a low or a high pressure. 



