110 Effects of Lightning on Wood, 



On the 20th of July of the same year the lightning struck a 

 large oak in the forest of Rambouillet. On this occasion the 

 branches were totally separated from the trunk, and dispersed 

 around with a certain degree of regularity. They did not appear 

 to be withered, and their bark seemed sound. The trunk itself 

 had not been pealed clean, but, hke the oak of the island Adam, 

 it had become a mere bundle of laths : there was also this dif- 

 ference, they were prolonged in this form to the very ground, 

 instead of the process being arrested at a certain height. 



I cannot resist the desire I feel to cite a third case, of which 

 Professor Munke has given an account, in Poggendorff's 

 Annals. The diameter of the oak examined by the Ger- 

 man philosopher was upwards of three feet, at the level of the 

 ground. The entire trunk of this great tree disappeared ; or, 

 to speak more accurately, the lightning had separated it in- 

 to shreds many yards long, and between a line and a line and 

 a half in thickness, similar to the portions that a gouge would 

 have detached. Three branches, from 20 to 24 inches in dia- 

 meter had fallen vertically, cut clean through as if by a single 

 stroke of a hatchet ; they preserved their leaves and branches. 

 Not the slightest traces of inflammation or carbonization were 

 perceived. The total absence of carbonization, the division of 

 the trunk of the tree into such numerous and delicate filaments, 

 the dispersion of these filaments into a thousand different di- 

 rections, all this, I repeat, appears to be the necessary conse- 

 quence of the action of some elastic force which had developed 

 itself between the fibres of the wood. By means of a flash of 

 lightning suddenly transformed into steam, the hygrometric wa- 

 ter which is contained in the old rafters of a roof, and in the sap 

 which fills the longitudinal capillary tubes of a growing tree, 

 and you will produce in every particular the phenomena of the 

 rafters at the Abbey of St Medard de Soissons, and of the oaks 

 of the island Adam, of the forest of Compiegne, &c. &c.* 



* Lightning often strikes trees quite dead, whilst the external and con- 

 spicuous damage is altogether trifling. Mr Tull, the author of The Philo- 

 sophy of Agriculture^ is of opinion that this effect is the consequence of the 

 rupture of the small vessels, across which the lightning has forced its way. 

 According to our view, the lightning in this case acts mechanically, as does 



