NATURAL PHILOSOPHY. 121 



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erations : " Steam-boilers are found, as regards electricity, in condi- 

 tions analagous to those of our hot-air chambers. It is probable even, 

 that with equal volumes they contain a much larger quantity. Is it 

 not natural that the phenomena which I have observed, as a matter of 

 chance, in our hot-air cylinders, should be sometimes reproduced in 

 steam-boilers ? It is known that explosions are more violent the 

 greater the amount of electricity ; and on the other hand, that the 

 quantity of electricity is greatest when the steam is of moderate ten- 

 sion, as in steamboats of low-pressure engines. And these low-press- 

 ure engines, are the ones which often explode, while the locomotives 

 which are high pressure, very seldom explode. In support of these 

 considerations, M. Andrand says, that he has more than twenty times 

 tried to burst vessels of thin sheet iron by compressing in them air at a 

 high temperature, and has not been able to succeed in tearing them, 

 except when the pressure was raised to 50 or 60 atmospheres ; twice 

 onl} r has he produced an explosion ; and those with vessels of copper 

 when other metals were present. Silliman's Journal. 



ELECTRICITY AND HEAT. 



M. Gaugain, of France, as the result of carefully conducted re- 

 searches, has recently informed the Academy of Sciences, that he does 

 not think the currenits developed in thermo-electrical batteries, viz., 

 in electrometers formed by the association of two different metals, 

 whose points of junction are maintained at different temperatures, 

 should be attributed to the motion of heat. He consequently sus- 

 pects all experiments, upon which experimenters have endeavored to 

 found the doctrine that the propagating motion of heat in the interior 

 of bodies disengages electricity. One of these experiments, how- 

 ever, is celebrated ; it constantly succeeds, but M. Gaugain interprets 

 it differently from every one else, and he especially prevents the 

 fundamental phenomenon appearing by changing the experimental 

 data, without, however, so changing, as to prevent the propagation of 

 heat. This is the experiment : A platina wire, with one extremity 

 inserted in the interior of a glass tube, closed with the lamp and blow- 

 pipe, is placed in connection with the plate of a condensing electro- 

 scope by its other extremity. The glass tube is surrounded in the 

 interior with a second platina wire, rolled spirally, and which commu- 

 nicates at one end with the earth. If the experimenter heats con- 

 siderably by a lamp's flame the metallic spiral, and the parts of the 

 tube enveloping it, it will be found that the plate of the electroscope 

 is charged with positive electricity. According to the theory of I\L 

 Becquerel, the author of the experiment, the heated spiral is the seat 

 of an electromotric force ; the negative fluid goes towards the 

 ground, following the same direction as the heat, and the positive 

 fluid, moving in an inverse direction, traverses the glass tube, 

 which has become a conductor in consequence of the elevation of 

 the temperature, and is conducted by the interior wire to the in- 

 strument which indicates its presence. To make this celebrated 



