APPENDIX TO MEMOIR OF PELTIER 195 



fundamental basis of all meteorolog}', we judge proper to recite it liere with 

 some details. 



A place is selected perfectly uncovered and commanding- all the environing 

 objects ; an electroscope is to be taken furnished with a stem of about four 

 decimetres, surmounted l>y a ball of polished metal of a radius of from three to 

 four centimetres, with a view to augment the effects of influence and to avoid 

 the efflux of tlie electricity which may be repelled into the upper ])art; the 

 instrument is to be held with one hand, the equilibrium to be managed with the 

 other, in putting in connnunication the stem and the foot. All the reac- 

 tions being equal on one part and the other, the gold leaves of the electroscope 

 fall straigiit and mark zero. In this state of equilibrium the instrument may 

 be left in contact with the free air for a whole day under a clear sky without 

 the least sign of electricity being manifested ; it may even be moved and the 

 air agitated ; as long as the instrument is kept at the same altitude it remains 

 completely insensible. But if, instead of leaving it in the same horizontal stra- 

 tum of air, it be elevated from four to five decimeters, the gold leaves arc at 

 once seen to diverge and to indicate a vitreous tension. If the instrument be 

 replaced at the point of departure the leaves again fall exactly to zero ; if it be 

 sunk lower than this point of equilibrium the leaves diverge anew, but now 

 they are charged with resinous electricity. On raising it again to the point of 

 departure the instrument resumes its zero, and retains nothing of the free elec- 

 tricities which it has for an instant shown. 



Since no free electricity has remained in the instrument the air has of course 

 communicated nothing to it, and the electrical signs which the instrument had 

 presented proceeded only from the electricity developed in its interior by the 

 influence of a neighboring body in proportion as it was brought nearer to or 

 removed further from it, by elevating the instrument above the point where it 

 had been in equilibrium or depressing it below that point : it sutflces, in effect, 

 to replace the instrument at the same point to cause them to disappear. They 

 were, I repeat, nothing more than signs of electricity by influence, such as may 

 be perceived in bodies which are brought near to or removed from another body 

 charged with free electricity, a phenomenon which may be reproduced in the 

 closet by placing one's self on a resinous or a vitreous surface. The conse- 

 quence of this experiment is that dry air is not electrical of itself; that the 

 earth has a resinous tension, and space a vitreous tension. We maj^, in effect, 

 interpret this experiment in relation to space, or in relation to the earth. In the 

 first case we say if, after having placed an electroscope in equilil)rium at a cer- 

 tain height, we raise it to a greater height, we approximate the terminal ball to 

 the celestial space or to the vitreous body. This latter then acts with more effi- 

 cacy ; it decomposes a portion of the natural electricity of the ball, attracts the 

 resinous and repels the vitreous in the gold leaves which diverge and indicate a 

 vitreous tension. In the second case we say if, after having placed an electro- 

 scope in equilibrium at a certain height, we raise it to a greater height, the 

 foot of the instrument, forming with the arm which lifts it the extremity of a 

 point more elevated and conducting, becomes charged thereby with a more con- 

 siderable resinous tension ; the resinous electricity thus accumulated in the pla- 

 tina and in the armatures acts now with more force, decomposes the natural 

 electricity of the upper part of the instrument, repels the resinous in the termi- 

 nal metallic globe, and attracts the vitreous in the gold leaves which diverge. 

 As may be seen, these two interpretations end in the same result ; but, accord- 

 ing to the ideas of Peltier on electricity, the last alone is logical and admissible. 



Peltier may be considered as the founder of meteorology. No doubt, before 

 him, a great number of distinguished savants had occupied themselves with this 

 branch of knowledge ; among the more recent it might suffice to mention 

 MM. de Humboldt, Boussingault, Kaemtz, Quetelet, Lamont, Arago, Gasparin, 

 &c., &c. But all these savants starting with the erroneous principle that the 



