258 Mr Charles Tomlinson on Lightning Figures.. 
originals which I produced in his presence, which I have no 
hesitation in pronouncing to be accurate. Since the date of 
these publications, M. Poey has brought out a new edition of 
his Memoir in a separate form, and has had the politeness to 
send me a copy, together with other meteorological papers of 
great interest and value. The Memoir now makes a small 
volume of 110 pages, and its title is as follows :—“ Relation 
historique et Théorie des Images Photo-électriques de la 
Foudre; observées depuis l’an 360 de notre ére jusqu’ en 1860. 
Par M. Andres Poey,” &c., Paris, 1861. 
Let us now return to these tree-like impressions produced 
by the discharge of a Leyden jar on the surface of glass. 
However rapid and instantaneous the discharge, time is occu- 
pied in making it. In the first place, the jar sends out 
ramifying feelers in all directions, to prepare the line of least 
resistance ; and this being accurately chalked out, the prin- 
cipal discharge takes place. In some cases the discharge 
bifurcates, and we then have two trunks, each with its own 
system of branches. I have also had instances of trifurca- 
tion, forming admirable illustrations of the modes in which 
lightning often attacks several points at once. That these 
feelers precede the main discharge, is evident from the fact, 
that should the glass be too thick, or present too large an 
area, these ramifications only are formed; we get, in fact, 
those lines which produce the sensation of cobwebs being 
drawn over the face, which seamen describe as the forerunners 
of the ship being struck. Another most important fact is, that 
the main trunk is hollow. The breath-figure shows this very 
decidedly ; it consists of two outer boundary lines, and two 
inner lines bounding a hollow core. I have made the dis- 
charge on a pane of smoked glass, and have thus obtained a 
permanent figure of the trunk, consisting of a couple of 
channels on each side of a black dotted line. Now, if we 
examine the stereotyped effects of a lightning stroke, as seen 
in the siliceous tubes or fulgurites, specimens of which are to 
be found in most museums, they too will be found to be 
hollow. The tubes found in a sandhill at Drig, in Cumber- 
land, are described in the “ Transactions of the Geological 
Society” for 1812 as being hollow, with a rough and uneven 
outer surface, containing deep furrows like the. bark of a 
