NATURAL PHILOSOPHY. 



ELECTRICAL DISCOVERIES. 



SIGXOR PALMIEHI, of Naples, has inrented a movable conductor a disk 

 of wood, bearing metallic points, rotating on an axis, which enables him 

 to correct the errors of former observers of electrical phenomena. The 

 idea of negative rains or cloud?, he says, must be given up, because the 

 differences observed are due only to time : for instance, the atmosphere 

 will be negative when a shower is approaching, positive while the rain is 

 actually falling, and negative again as it passes away. He hopes, by 

 means of his new instrument, to arrive at some of the laws which govern 

 the fall of rain in European latitudes. A curious fact has been noticed 

 also with respect to gutta-percha, which may be interesting to electricians. 

 This substance, as is well known, acquires a bluish tinge after having 

 been kept some months ; and when in this state, it can no longer be 

 negatively electrified, as before, by almost any substance with which it 

 may be rubbed. Its electricity is found to be positive ;. and the only 

 substances which will electrify it negatively are mica, diamond, and fur. 



M. Palagi, of Bologna, and M. Tolpicelli, of Home, sustain the opinion 

 that the change of distance between two bodies constitutes them in differ- 

 ent electrical states, as they are removed from or advanced to each other. 

 M. Volpicelli, while endeavoring to frame the experiment which shall 

 exhibit this phenomenon, has discovered a singular electro- static property. 

 When ail insulating stick of glass, or sealing-wax, or sulphur, is placed 

 on an insulated or non- insulated support, (e. $., sliding through one or 

 several rings,) the natural electricity of the stick is distributed by the 

 rubbing, which rises from the motion in a singular way ; the electricity 

 accumulates in one of the extremities of the stick, at the same time 

 diminishing in the other, so that there is a point between the two extremi- 

 ties in the normal state. If the stick is of glass, the extremity which is on the 

 side towards which the motion is operated presents positive electricity, and 

 the other extremity negative electricity ; the contrary takes place if the 

 stick is of wax or of sulphur. The new electro-static polarity manifests 

 itself in the extremities, even when the rubbing takes place only on a very 

 small part in the midst of the insulating stick, and when the extremities 

 themselves have no share in the rubbing. 



