226 Electrical Phenomena of Certain Bouses. 



electricity. So far as I have had an opportunity to judge, I infer 

 that heavy velvet carpets answer this purpose best. Two thicknesses 

 of Ingrian carpet answer very well. A drugget spread upon an 

 Ingrian carpet yields a good supply of the fluid. The effect of the 

 increased thickness is obviously to improve the insulation of the 

 carpet. 



2. The carpet must be quite dry, and also the floor of the room, 

 so that the fluid may not be conveyed away as soon as it is excited. 

 This will not generally be the case except in winter, and in rooms 

 which are habitually kept quite warm. The most remarkable cases 

 which I have heard of in New York have been of close, well-built 

 houses, kept very warm by furnaces, and the electricity was most 

 abundant in very cold weather. In warm weather only feeble signs 

 of electricity are obtained. 



3. The rubber, that is, the shoe, must also be dry, like the car- 

 pet, and it must be rubbed upon the carpet somewhat vigorously. 

 By skipping once or twice across a room with a shuffling motion 

 of the feet, a person becomes highly charged, and then upon bring- 

 ing the knuckle near to any metallic body, particularly if it have 

 good communication with the earth, a bright spark passes. In al- 

 most any room which is furnished with a woollen carpet, and is kept 

 tolerably warm, a spark may be thus obtained in winter ; but in some 

 rooms, the insulation is so good and the carpets are so electrical, that 

 it is impossible to walk across the floor without exciting sufficient 

 electricity to give a spark. 



It may be said that in this case there can be but very little 

 friction between the shoe and the carpet. But it must be remem- 

 bered that the rubber is applied to the carpet with considerable force, 

 being aided by the whole weight of the body, so a slight shuffling of 

 the feet acts with great energy. 



In the London and Edinburgh Philosophical Magazine for Feb- 

 ruary 1839, is given an account of a leather strap connecting the 

 drum of a worsted mill, which gave sparks two inches in length, and 

 charged a battery in a short time. The strap was twenty-four feet 

 long, six inches broad and one eighth of an inch thick. It crossed 

 in the middle between the two drums, the strap forming a figure 8. 

 Here there was considerable friction, since the strap made one hun- 

 dred revolutions in a minute. 



In the American Journal of Science for July 1840, is mentioned 

 an instance of a leather band in a cotton factory, which exhibited 

 strong electrical excitement. 



These examples shew that leather, when subjected to considerable 

 friction, yields an abundant supply of electricity. 



In the Proceedings of the American Philosophical Society for De- 

 cember 1840, arementioned several cases of individuals who drew sparks 

 of electricity from a coal stove and from a common grate. I consider 

 it probable that in those cases the experimenter was the electrified 



