342 Proceedings of the British Association for 1850. 



lightning strokes ; several other trees having been destroyed 

 there since 1834. The tree examined by the Committee was 

 struck on the 11th of June 1849, on a still sultry day. It is 

 an oak tree. It stood in rather a clear space — the surround- 

 ing trees being chesnut, elm, &c. It was a large tree (14 

 feet in girth), but there were others as high, and of rather 

 greater diameter. When struck it was full of sap. The 

 mechanical effects of the lightning were violent. The main 

 trunk of the tree, which appears to have stood about 12 feet 

 high before sending off branches, was rent from top to bot- 

 tom ; some of the branches were broken off; all were thrown 

 down and implicated together, and for some distance upward 

 fissured and twisted ; some of the roots were split for a yard 

 or more from the stem. A large mass from the northern 

 side of the tree was driven out, and carried through the air 

 127 feet, in the direction of the magnetic meridian to NNW. 

 Its weight was 2^ cwt. The main stem was entirely denuded 

 of the bark, which was scattered widely around, but most 

 abundantly in a direction opposite to that in which the log 

 of wood was conveyed. Shreds of wood were scattered to 

 the north-west, and left hanging in the trees. What re- 

 mained standing of the stem, as well as the parts which had 

 been displaced, was cleft into wedges, by vertical radiating 

 fissures parallel to the laminae of medullary rays; and 

 these wedges were again cleft by other vertical fissures 

 concentric to the axis of the tree, and coinciding with the 

 annual bands of large vertical vessels, which are conspicuous 

 in cross sections of the oak. Where these cleavages pro- 

 duced the fullest effect, the wood was divided into long 

 slender prismatic shreds like lucifer matches. The smaller 

 split masses were much twisted. For all these phenomena 

 a simple mechanical cause appears sufficient, viz., an internal 

 expansion and bursting of the main stem of the tree along 

 the surfaces, which, by the. structure of the tree admitted of 

 the most easy separation, and contained at the time abund- 

 ance of liquid sap capable of assuming the form and force of 

 elastic vapour. Hence, in the first place, the destruction of 

 the main stem by explosion — the projection of the bark and 

 woody fragments, and the minute and regular cleavage of the 



