328 Intelligence and Miscellaneous Articles. 



in a point or a ball, and the lower end in a gold-leaf electroscope, it 

 seldom showed the existence of atmospheric electricity. But when 

 the lower end was connected with a dry pile condensing electroscope, 

 signs of electricity were always obtained, sometimes positive and 

 sometimes negative ; and this is the only means by which, with a 

 fixed rod, the nature of the atmospheric electricity may always be 

 obtained. Before commencing the experiment, it must be ascertained 

 if the instrument is in the natural state ; this is the case when, after 

 touching both plates and then separating them, the gold leaf remains 

 at rest. In the second place, the electricity must be collected first 

 by the upper, and then by the lower plate, in order to ascertain that 

 the two results agree. After each experiment both plates of the 

 condenser must be connected with the ground, and separated from 

 one another by an uninsulated metallic foil. These precautions are 

 essential in detecting the small traces of electricity usually met with 

 in the atmosphere. 



2nd. The nature of the atmospheric electricity sometimes varies 

 four or five times in the space of three or four minutes. 



3rd. The electricity is the same, whether the rod terminates in a 

 point or in a ball ; the quantity varies little, but seems less with a 

 ball than a point. 



4th. When a flame, or an incandescent ball, or even ignited 

 charcoal is placed on the point, the electricity which was negative is 

 changed into positive. If the atmospheric electricity is positive, 

 flame and incandescent metals simply increase the intensity. The 

 hotter the flame, the greater the quantity of electricity. The effects 

 of a spirit-lamp exceed those of an oil-lamp. Hence flame is liable 

 to introduce a source of error, when used in making observations on 

 atmospheric electricity. 



5th. If, in some very rare cases, flame does not change the nega- 

 tive electricity exhibited by the point into positive electricity, it not 

 only does not increase the tension, but seems to diminish it, and 

 thus another source of serious perturbations is introduced into the 

 observations. 



6th. In a room and by the methods described, the author has 

 always obtained traces of positive electricity by means of flame. — 

 Comptes Rendus, July 16, 1860. 



MAGNETIC PHENOMENON. 



M. RuhmkorfF has the following notice in the Comptes Rendus, 

 vol. 1. p. 1 66 : — " If a stay (bride) of soft iron be pressed against 

 one of the poles of an artificial magnet, the soft iron is observed 

 to become hard, it is more difficult to file. If the stay be removed, 

 it loses its hardness and resumes all the properties of soft iron." 



