PROTECTION FROM LIGHTNING. 



Danger proportionate to the Magnitude, not to the frequency of the Evil. Ancient Methods of avert- 

 ing Lightning. Persons in Bed not Secure, as some think. Augustus's Sealskin Cloak as a Light- 

 ning Protector. Influence of Color on the Electric Fluid. Tiberius's Crown of Laurel as a Light- 

 ning Protector. The Danger of taking Shelter beneath Trees. Futility of taking Shelter in Glass 

 Cages. Metal about the Person destroyed by Lightning. Metal Appendages to be laid aside. 

 Lightning Explosions occur at the Points where it leaves or enters a Metal. Part of a Room 

 which is most Safe. Lightning more likely to discharge among a Crowd than on a single Individ- 

 ual. Influence of the Vapor of Transpiration, &c. Certain Individuals are comparative Non- 

 Conductors. Thunder-Clouds have been traversed with Impunity. Thunder-Storms below the 

 Place of Observation. PARATONNERRES, or Lightning Conductors. Lightning Conductors pro- 

 tective even when no Flash strikes them. Sparks at the Interval where a Conductor is dis- 

 jointed. Lightning Conductors drain off the Electricity of Clouds. Sparks or luminous Aigrettes 

 on the Point of Conductors. More frequent Occurrence at Sea, Influence of Elevation of a Par- 

 atonnerre. Experimental Illustration. Electric Kites. Captive Balloons as Paragreles and for 

 Meteorological Research. Pointed and blunt Conductors. Quantity of Lightning drawn down 

 by a Conductor. Mr. Harris's Conductors for Ships. Assumed Extent of the protecting Power 

 of a Paratonnerre. Not based on experimental Grounds. Cases against its general Application. 

 Lightning does not alway strike the highest Points. Lightning Conductors with many Points. 

 A Lightning Conductor must have sufficient Capacity. A Lightning Conductor must bo in good 

 Connexion with the moist Sub-Soil. Charcoal Beds to receive the Base of the Conductor. Vici- 

 nal metallic Conductors. Conductors of metallic Wire- Rope ; Insulation not needed. Conduct- 

 ors for Powder Magazines. Efficacy of Lightning Conductors. Lateral or divided Discharge 

 defined ; its Cause. More readily obtained from Conductors than from Leyden Discharges. 

 Line or Lines of least Resistance. Absolute Necessity of connecting the Conductor with vici- 

 nal Bodies. Artificial Means of producing the Electrical Odor. Chemical Changes. Fusion. 

 Fulgurites. Mechanical Effects. Effects of conducting Bodies. 



VOL. II.-7 



