202 
THE GEOLOGIST. 
sand by Mr. Darwin ; but, as the diameter of the whole was nearly- 
equal, it must liave extended to a greater depth. He found one 
deviating from a riglit line at a considerable bend, amounting to 33°; 
and from this tube two small branches about a foot apart were sent 
off, one pointing downwards and the other \ipwards. Tiiis is an 
illustration of the forked character of the electric fluid, which, besides 
its division into two branches, would seem to have turned back in this 
case at an acute angle of 2G° to the line of its main course. At Drigg 
many tubes were found dividing into two branches and pursuing a 
tortuous course into the sand. Some of the tubes gave off several 
small branches, the diameter of which was not a fifth of the tube 
whence they sprang ; othei-s, again, deviated almost at right angles, 
glancing off, as it seemed, by the interruption of a pebble, as in the 
example figured in the Geological Society's Transactions (vol. v. First 
Series, pi. 3). 
It is looked upon as a fact somewhat remarkable, that quite a 
number of tubes have been discovered to enter the surface of these 
sand-hills in comparatively limited areas ; at least, such was the case 
at Drigg, on the shores of La Plata, and also in Gennany. Mr. 
Darwin counted more than four within a space of sixty yards by 
twenty. Three were noticed within an ai-ea of fifteen yards, upon 
a single hillock at Drigg ; and the same number were found in an 
equally limited space in Germany, as described by M. Ribbentrop. 
In considering this peculiarity, Mr. Darwin believes in the improba- 
bility of these tubes being produced by successive and distinct shocks 
— an opinion in which most persons will concur. Yet, whilst acknow- 
ledging the possibility of a division of the lightning into separate 
branches shortly before entering the ground, as suggested by him, I 
still think that the electric fluid may have run along the surface of 
the sand, and then entered it at different spots remotely situated 
from one another. This view is by no means irrational, when we 
reflect upon the truly singular peculiarities associated with this won- 
derfid fluid, which may be seen at times to run along the surface of 
bodies and suddenly disai:)pear. The intensity of its action, too, is 
oftentimes modified hy the amount of resistance offered by substances 
struck by it. On the other hand, the electric fluid may divide into 
