British Works. 285 



The falling of the drops opens a communication by which the electricity 

 accumulated in the cloud is restored to the earth by conduction. When the 

 intensity of the electricity is great, however, it may overcome the resistance 

 of the air, and, by discharging itself, hasten the commencement of the shower, 

 or even determine the precipitation of a cloud, which might otherwise have 

 evaporated. As the temperature arrives at its maximum at the same time of 

 the day, it is not surprising that the transient storm should occur at the same 

 hour of the day during the continuance of the same kind of weather. This 

 has been observed to happen even in our variable climate, on three or four 

 successive days. 



" The intensity of the electricity of the atmosphere has been found by Mr. 

 Crosse to be according to the following order of kinds of weather : — 



1. Regular thunder-clouds. 10. Sky obscured by clouds. 



2. Driving fog, with small rain. 11. Mackarel, or mottled sky. 



3. Fall of snow, or brisk hail storm. 12. Sultry weather, with light hazy 



4. A smart shower, in a hot day. clouds. 



5. A smart shower, in a cold da_y. 13. Cold damp night. 



6. Hot weather, after some wet days. 14. Cold dry east winds, affecting the 



7. Wet weather, after some dry days. feeling to a degree not cor- 



8. Clear frosty weather. responding with the ther- 



9. Clear warm weather. mometer." 



The weakness of the electricity which is diffused through the atmosphere 

 makes it incredible that it can have any of the effects which popular opinion 

 ascribes to it, under the designation of " thunder in the air." It is said to 

 blight vegetation, to taint butcher's meat, to turn milk sour. We may, with 

 more reason, ascribe these effects to the high temperature and humidity than 

 to electricity, which is more intense in a snow storm or a hail shower (as may 

 be seen in the preceding table), than in the kind of weather in which they are 

 produced. With respect to its supposed influence on the human health, the 

 same causes, combined with diminished pressure, are sufficient to explain the 

 sickness, low spirits, nervousness, and feeling of general discomfort, arising 

 from the contrary actions of stimulation from heat, checked perspiration, and 

 more languid circulation. 



The meteorological phenomena caused by simple communicated electricity 

 are somewhat interesting, and are quite harmless, but often give rise to ground- 

 less terror among the ignorant or superstitious. 



These we must pass over, noticing only a remarkable instance of the elec- 

 tricity which may precede a storm, before any threatening appearances are 

 seen. On one of the bastions of the Castle of Duino, on the shores of the 

 Adriatic, there had existed from time immemorial a pointed iron rod, placed 

 vertically. In the summer, when an approaching storm was apprehended, the 

 sentinel on the bastion presented a halbert to the iron, and when he per- 

 ceived it to emit sparks or display a small sheaf of fire, he rang a bell to give 

 notice to the country people in the fields, and the fishermen at sea, to seek 

 shelter from the approaching storm. 



The writer next considers atmospherical electricity in a state of local accu- 

 mulation in clouds, in which the intensity of the charge in the cloud is 

 ultimately determined by the rapidity of the condensation of the vapour, and 

 the distance of the cloud from the earth or conductors. The destructive 

 powers of electrical discharges are to be estimated, not by the intensity of the 

 charge within the cloud, but by the quantity ; for the greater part of the 

 charge of an extensive cloud may be concentrated into a flash of lightning of 

 small dimensions. " The force of the electricity is proportionate to the square 

 of the thickness of the stratum, and, clouds being most frequently of a flattened 

 form, there is a tendency to diffusion or discharge rather from the edge and 

 circumference than from the central part." " The path of the electricity is 

 not a straight line between the discharging points ; but it is never capricious, 

 being previously probed, as it were, by the subtile fluid which penetrates all 



