SCIENTIFIC TRACTS. 



NUMBER XX. 



ELECTRICITY. 



INTRODUCTORY REMARKS. 



MANY centuries ago it was noticed that a certain sub- 

 stance called amber had a very peculiar property. When 

 it was rubbed upon dry cloth or flannel, it had the power 

 of attracting light substances. Feathers, down, and par- 

 ticles of dust would adhere to it, and if removed, they 

 were drawn forcibly to it again. The Greeks first ob- 

 served this phenomenon. The Greek name for amber 

 was E/cktron. Hence they expressed this attractive pow- 

 er, by the term Electricity, or rather by a term from 

 which the English word electricity has, by a slight 

 change of form, been derived. 



Amber is not a very common substance in our country, 

 but the above experiment may in substance be tried by 

 any one, with a peice of resin or gum of almost any kind, 

 for almost all resinous substances possess this power. 

 Spread upon a table a little lint, or a few fibres of cot- 

 ton, or the light downy part of a feather ; then take 

 a piece of resin having a smooth surface, and after warm- 

 ing and drying it, rub it briskly upon a piece of woollen 

 cloth or dry flannel. Upon bringing it, then, near the 

 light substances before mentioned, they will be found to 

 be attracted towards it, and will adhere to it a long time. 



The reason why light substances are used in this ex- 

 periment, is not that they are more strongly attracted 

 than others, but because they may more easily be moved 

 by the attraction, and consequently the effect will be more 

 manifest. The resin will attract a steel needle as strong- 



VOL. r. NO. xx. 42 



