Direct Action of Electrical Storms. 115 



the middle of the length of the cleavage, and the top is not 

 carried off as in the decapitated trees. 



A still more essential character is, that these laths and 

 splinters are completely dried immediately after the passage 

 of the meteor. M. Preisser assured himself of this at Mont- 

 ville ; MM. Decaisne and Bouchard in the trunks struck by 

 the storm at Chatenay ; M. de Gasparin in the poplars broken 

 by the storm of Courthezon. The dryness of these splinters 

 renders them extremely fragile. M. d'Arcet found only 

 7 parts in 100 of water in the cleft trunks of Chatenay. Now, 

 standing trees contain from 30 to 40 parts in the 100 ; and 

 such as have been felled for five years still contain from 24 

 to 25 parts in 100. The bark of the cleft trees is split, torn, 

 rolled upon itself, and cut into shreds, adhering to the tree or 

 scattered around it. 



A fact related by M. Boussingault perfectly explains this 

 evaporation of the sap under the influence of electricity. On 

 the 22d May 1842, the lightning fell upon a large pear-tree, 

 at Bechelbronn in Alsace ; a thick column of vapour, like the 

 smoke which issues from a forge fed by coals, arose, and splin- 

 ters of wood were thrown to a distance of many metres ; the 

 bark had disappeared ; the tree appeared entirely white. M. 

 Boussingault does not doubt that it was the vapour of water 

 which made this tree fly in pieces. I am entirely of this 

 opinion. It appears to me that cleft trees may be compared 

 to boilers burst by the expansion of steam. 



In cleft trees the sap mostly evaporates, the trunk is split 

 into a thousand pieces, and the wind acts on the cleft por- 

 tion, which evidently offers less resistance than the rest of 

 the trunk. This evaporated sap resembles thick smoke, hence 

 the mistake of the onlookers at Montville, who all supposed 

 that a fire had broken out in the forests over which the storm 

 passed. 



The deep colour of the evaporated sap was probably owing 

 to the eai*thy particles which the wind and the electrical 

 attraction raised into the air. Lastly, to finish the demon- 

 stration, MM. Becquerel, father and son, have succeeded in 

 reproducing, by means of strong electrical discharges, clea- 

 vage of trees, in branches of tlie size of the little finger. 



