258 Mr. F. Guthrie on a Relation between 



the leaves. It is in fact impossible to use a white-hot iron ball 

 as a ( ' proof plane " for + electricity. 



§ 2. Experiment. — A white-hot iron ball being hooked out of 

 the fire, as in § 1, by the insulating hook, is made to touch the 

 — conductor of the machine ; it is then found to be incapable 

 of influencing the electroscope by induction or by contact. The 

 white-hot ball cannot serve as a proof plane for — electricity. 



§ 3. Experiment. — On the top of the electroscope is placed a 

 wooden block covered with tinfoil. Above this are a few sheets 

 of metal plate. Upon these is a tripod stand inverted, to which 

 a metal chain is fastened. The other end of the chain can be 

 connected with the + or — conductor of an electric machine. 

 A white-hot iron ball is placed on the tripod, and the chain is 

 fastened to the + conductor. As long as the machine is worked 

 the leaves diverge; but on ceasing, they immediately drop together. 



§ 4. Experiment. — The arrangement being precisely the same 

 as in § 3, the chain is fastened to the — conductor of the ma- 

 chine. As before, the leaves only remain divergent while the 

 machine is being worked. 



§ 5. Experiment. — The chain in § 3 being removed, the white- 

 hot ball is placed upon the tripod. It is found impossible to 

 make the leaves diverge by a charge from a proof plane of 24- 

 inch surface which has been charged by either the + or — con- 

 ductor and then brought into contact with either the white-hot 

 ball or any other part of the electroscope's system. 



§ 6. Experiment. — A white-hot iron ball on a metal hook (so 

 as to be in earth- connexion) is held above the top of an electro- 

 scope charged with + electricity. When at the distance of one 

 or two inches, the leaves rapidly and completely collapse, and do 

 not recover their divergence on the removal of the ball. 



§ 7. Experiment. — The electroscope is charged with — elec- 

 tricity, the conditions being otherwise as in § 6. When the ball 

 is at a distance of three or four inches the electroscope is rapidly, 

 completely, and permanently discharged. 



§ 8. Experiment. — The electroscope being charged with + 

 electricity, the white-hot iron ball is hooked out of the fire with 

 the insulating hook and brought above the electroscope. Perfect 

 and permanent discharge takes place when the interval between 

 the two is about one inch. 



§ 9. Experiment. — -The electroscope is charged with — elec- 

 tricity, the experiment being otherwise as in § 8. The electro- 

 scope loses its charge completely and permanently when the 

 interval is two or three inches — that is, sensibly greater than 

 with -f electricity. 



§ 10. Experiment. — An iron wire with a little cotton-wool 

 fastened to one end is dipped into benzol, ether, alcohol, or bi- 



