^58 Scientific Intelligence. — Natural Philosophy. 



nished, and may even be reduced to 0° ; in the latter, this 

 action is much more moderate. 2dly, Temperature acts mecha- 

 nically in dilating or contracting the pile, and consequently in 

 augmenting its energy by the greater pressure which the ele- 

 ments undergo when the pile elongates, or in diminishing it, 

 when the contrary effect takes place. It also acts upon the 

 function of the pile, by favouring the chemical action which 

 electricity produces. 3dly, Temperature does not produce its 

 effects suddenly, but only after a certain time. It does not act 

 in an absolute manner ; in other words, such a degree of tension 

 does not answer to such a degree of the thermometer, but its 

 action has relation to the temperature which has existed some 

 hours before. 4thly, Heat frequently only increases the rapi- 

 dity of the current, and not the quantity of the electricity t^yo- 

 duced.— Atmospheric Electricity. The question whether the 

 electric state of the air and the other meteorological phenomena 

 have a direct influence upon the tension of dry piles, is un- 

 doubtedly the most interesting and the most difficult to be sol- 

 ved. It is evident that the causes hitherto preferred are incap- 

 able of accounting for all the variations that are observed in 

 the tension of the piles. It is in the electrical influences then 

 that we are to seek the explanation of the anomalies which their 

 action presents .'' On this subject experiment gives the follow- 

 ing results : If, by means of the electric machine, positive elec- 

 tricity is made to arrive at the negative pole, the tension aug- 

 ments considerably at the positive pole, while, if it is at the posi- 

 tive pole that positive electricity is made to arrive, the tension 

 is reduced to 0° at the negative pole. In a word, electricity 

 arriving at the pole of the same name, reduces the tension of 

 the other pole, and electricity arriving at the pole of the contrary 

 name, augments the tension of the other pole. Now, the piles 

 which are observed being commonly placed under a glass globe, 

 and communicating by one pole with the reservoir, and the other 

 being isolated in a medium little accessible to humidity, it is not 

 therefore to the latter that the electricity can be transmitted, and 

 its action can only be conceived by supposing that it comes 

 from the earth. But does it not in fact happen, that when an 

 electric cloud approaches the earth, a certain quantity of the 

 natural fluid of the common reservoir is decomposed, and at- 



