Proceedings. 7-3 



recent paper on " The Damage by Lightning to Trees," pub- 

 lished in the Yahresheft des Vereins fur vaterlandiscJi Natur- 

 kunde in Wiirtembiirg, 1893. Mr. Tonesco's conclusions are 

 that the amount of water contained in the wood of various 

 trees does not cause the difference in liability to be struck, 

 which is noticeable in trees, but that the presence or absence 

 of oil in the wood is the chief cause of this difference. Fischer 

 had shown {PringsheinCs Yahrbuch, 1891) that the reserve 

 starch contained in the wood is in many trees converted 

 into oil, which, being a bad conductor, protects these trees 

 from lightning, which would select those trees which are 

 the best conductors. Thus beeches, in which oil is present 

 in large quantities, are very rarely struck by lightning, while 

 oaks are, perhaps, the most frequently damaged by this 

 cause. Among the conifers the Scotch fir, in which the oil 

 disappears in the summer, is more liable to be struck than 

 the stone pine, in which a considerable oil remains in the 

 summer. For these reasons trees are worse conductors in 

 the winter than in the summer, and are also less frequently 

 injured by lightning in winter thunderstorms than in those 

 taking place in the summer. The course taken by the 

 lightning is, as Cohn had shown, along the cambium, which, 

 containing most water, is the best conductor. The sub- 

 stratum on which the trees are growing is in no direct 

 connection with the frequency of injuries by lightning. 

 The leafy portion of trees, being a bad conductor, is usually 

 not struck, the lightning striking below the main branches, 

 but if the leaves have been thoroughly wetted the lightning 

 often strikes this upper portion of the tree. Dead branches 

 seem to attract the lightning most frequently, both in trees 

 which are rich in oil, and such as are poor in that substance. 

 Dr. G. H. Bailey remarked that pines appeared to be 

 peculiarly liable to lightning strokes, and Dr. BOTTOMLEY 

 suggested that this might be a consequence of the pointed 

 form of the leaves. 



