Lesson IV. 



ELECTRK 



139 



placed upon the uppi-r surface of the elec- 

 trical plate. 



! >w is the electrophorus used ? 



P. ] M removed, and the sur- 



: :he shell-lac struck pretty smartly 



of dry silk, fur, or cat's-skin, 



so as to make it negatively electric ; after 



which the cover is replaced. The elec- 



of resin acts inductively 



he two electricities hitherto cora- 



r; the + electricity is 



d, and will he found in the lower 



ver, and the electricity is 



1 and accumulates in the upper part 



. [Exp. 9.] Ym observe that 



i electrophorus, and now 



I will brin^r my knuckle near the cover. 



f Does so, and a spark is elicited.] If I 



now touch the cover with my fin. 



: ;city will escape, and the + 

 ity remain in combination with the 

 tricity of the resin as long as the 



son. If the cover is rei 

 the + electricity will be set free, and we 



can then get a spark of + electricity from 

 the cover. 



UAL QUESTIONS ON LESSON III. 



1. What is the effect of an electric body 

 being placed near to a body in a natural 

 condition ? 



2. If we place any body charged with 

 only one kind of electricity near to other 

 bodies, what will be the e'ffect, provided 

 the electrical body does not touch the 

 others 't 



.",. Kxplain the meaning of induction. 

 4. What di>es the intensity of electrical 

 I disturbance depend upon ? 



\ plain the use and action of the 

 -cope. 



6. What are the usual means of develop- 

 ; ing fractional electricitv ? 



\ plain the various machin. 

 for frictional electricity, and how they act. 



8. What is the electrophorus, i 

 and mode of action ? 



LESSON IV. 



Our purpose is not to consider the difficult or abstruse matters relating to the laws 



tricity, but rather to give a general outline of its leading features, which will 



bear the same n sembl. -abject that a skeleton map does to a complete one. 



*, six times the size of our complete volume, would scarcely cont.iin the index 



to electrical science; and, therefore, where our readers imagine they discover neglect, 



it to want of space than lack of knowledge.* 



* now that aa the distance increases between hex! n and 



repulsion diminish; this is proved by the oscillations of an rlec-rie pendulum. 



As long M a body remains in a natural condition, that is, as long kinds 



of electricity are unc< is probabK . are uniformly dist: 



through the whole mass of the body. When the two kinds of electri- 

 separated, and a conductor is charged with free electricity, the individual elements of 

 these freed '. ^ ill repel each other, and continue separating until checked by 



This is the reason that electricity is disinhutfd ov<-r the sa r:'.ice of a 

 because, M the body is a good conductor, it does not hinder the dispersion 



QUESTIONa 



43. 7*.- !) the form of a body in- I P. Yes; the more round a bod> 



flmnce tin- di-triUn:.ii <-f U-etrieity ? | better, for as it departs from a round t 



tDr*TiiEaWiitT*BiA, feeling the* ted ofany proclir*/ irorlr on tclf 



Sfluncncrt MiiMof papm on " Practical Science," in the new (tries of the Famiig />,<*, 

 led an Appendix to the present rUrhUai, and an Introduction to other in> 



