Fig. 4. 



Fig. 5. 



THUNDER AND LIGHTNING, AND THE 

 AURORA BOREALIS. 



1. Atmospheric Electricity. 2. The air generally charged with positive 

 electricity. 3. Subject to variations and exceptions. 4. Diurnal 

 variations of electrical intensity. Observations of Quetelet. 5. 

 Irregular and local variations and exceptions. 6. Variations 

 dependent on the season and weather. 7. Methods of observing 

 atmospheric electricity. 8. Methods of ascertaining the electrical 

 condition of the higher strata. 9. Remarkable experiments ot 

 Romas, 1757. 10. Electrical charge of clouds varies. 11. Thunder 

 and lightning. 12. Form and extent of the flash of lightning. 13. 

 Cause of the rolling of thunder. 14. Affected by the zigzag form of 

 lightning. 15. Aifected by the varying distance of different parts of 

 the flash. 16. Affected by echo and by interference. 17. Inductive 

 action of clouds on the earth. 18. Formation of Fulgurites explained. 

 19. Accidents of the surface AThich attract lightning. 20. Lightning 

 follows conductors by preference its effects on buildings. 21. Con- 



LARDNER'S MUSEUM OF SCIENCE. N 177 



No. 130. 



