SCIENTIFIC RECREATIONS. 



Lightning conductors are such every-day objects that no description is 

 necessary ; but the reason the lightning runs along it harmlessly is because 

 the galvanized iron rod is the best conductor in the immediate neighbour- 

 hood. Where there is not a good conductor lightning will accept the next 

 best, and so on, any conductor being better than none. The point of the 

 rod cannot contain any electricity, there being no room for it, and the 

 " fluid," as it is termed, runs down to the ground, to terminate, when 

 possible, in water or charcoal. A great deal of electricity is no doubt 

 carried away from the air by the numerous conductors without any spark 

 passing. Until Sir W. Snow Harris brought forward his lightning con- 

 ductors for ships, the loss was great at sea. But now we rarely hear of 

 any vessel being disabled by lightning. We owe to Franklin the idea of 

 the lightning conductor. 



According to observations made by Mr. Crosse, the following statement 

 shows the tendency of the atmosphere, in certain conditions, to thunder- 

 storms. We may accept the deduction of M. Peltier that grey and slate- 

 colour clouds are charged with negative, and white, rose-colour, and orange 

 clouds with positive electricity. The order of arrangement in the following 

 table places the most likely source of thunderstorms first, and the least 

 likely source at the end, with regular rotation of intermediate probabilities 

 intervening : 



1. Regular thunder clouds. 



2. Driving fog with small rain. 



3. Fall of snow, or hailstorm. 



4. Smart shower on a hot day. 



5. Smart shower on a cold day. 



6. Hot weather after wet days. 



7. Wet weather after dry days. 



8. Clear frosty weather. 



9. Clear warm weather. 



10. Cloudy days. 



11. " Mackerel" sky. 



12. Sultry weather and hazy clouds. 



13. Cold damp night. 



14. Cold, dry north-cast winds. 



We have thus briefly touched upon some of the atmospherical phenomena 

 directly attributable to electricity. In our articles upon Meteorology we 

 will consider the aurora and many other interesting facts concerning the 

 atmosphere, and the effects of sound, heat, and light upon the air. 



Fig. 292. Lightning conductor. 



