Improvements in Science. J 23 



5. Atmospherical Electricity . — M. Matteuci has lately made 

 some interesting experiments upon this subject. They were 

 conducted, in what is termed in Italy, an English wood 

 (that is, one of small extent) consisting of Robinia pseu- 

 dacacia, Platinus Occidentalism Gleditzia triacanthos, Melia, 

 6fc. The electroscope with which the experiments were 

 made consisted of a stem of wood, at the extremity of which, 

 was placed a common lamp ; a copper wire conducted the 

 electricity from the flame to an electroscope. On rainy or 

 windy days, a very thin portion of phosphorus was sub- 

 stituted for the lamp, and was kept in a tube of glass 

 terminating in a point. He found, that whenever the 

 electricity of the atmosphere is positive, (which is always the 

 case in calm weather), it is impossible to have any traces 

 of electricity in the interior of a wood. The most curious 

 mode of observing it, is to move, carrying the electroscope 

 in the hand, either out of the wood, or above the leaves. 

 The flame is scarcely removed 10 paces from the trees, when 

 traces of electricity begin to appear. These increase with the 

 distance. In returning, the first tree is scarcely reached, 

 when the electroscope ceases immediately to indicate the 

 presence of electricity. These general results can only be 

 explained by one of two hypotheses ; either, that the electri- 

 city of the air is discharged by the leaves and the vapour 

 of water, and escapes by this means into the earth, or, 

 that there is developed by the effect of vegetable life, — by 

 the respiration of plants, enough of negative to neutralize 

 the positive electricity of the surrounding air. The second 

 hypothesis appears most plausible, because it is difficult to 

 admit the second, when we attend to the conducting power 

 of the flame, and of the column of hot air which is much 

 superior to that of the leaves. 



The results of a great number of observations showed, 

 that in the night, signs of electricity are often absent, both 

 in the air, and in the interior of a wood. At the approach 

 of day, before the sun appears above the horizon, decided 

 indications of negative electricity appear among the trees, 

 while none are detected in the open air. We can readily 

 understand this observation, if we admit that oxygen is 

 disengaged from the leaves before the rays of the sun strike 

 them directly. In this case, negative electricity appears. 



