24 SEVENTH REPORT—1837. 
rod between the ground and the ball, but from the part above, even 
to the top ofthe rod. Some remarks were then made on the theory of 
thunder-storms, as given by the French writers, in which the cloud 
is considered as analogous in action to one coating of a charged glass, 
the earth the other coating, and the air between as the non-conducting 
glass. One very material circumstance has been overlooked in this 
theory,—namely, the great thickness of the intervening stratum, and 
the consequent great quantity of free or redundant electricity in the 
cloud. This must modify the nature of the discharge from the 
thunder-cloud, and lead to doubt if it be perfectly analogous to the 
discharge from an ordinary Leyden jar, since the great quantity of 
redundant electricity must produce a comparatively greater lateral 
action ; and hence, possibly, the ramifications of the flash and other 
similar pheenomena may be but cases of the lateral discharge. 
Some facts were then mentioned, on the phenomena of the spark 
from a long wire charged with common or atmospheric electricity. 
It is well known that the spark in this case is very pungent, resem- 
bling a shock from a Leyden jar. The effect does not appear to be 
produced, as is generally supposed, by the high intensity of the elec- 
tricity at the ends of the wire by mere distribution, since this is in- 
compatible with the shortness of the spark. In one experiment, fifteen 
persons, joining hands, received a severe shock, while standing on the 
grass, from a long wire,—one of the number only touched the con- 
ductor; the spark in this case was not more than a quarter of an inch 
long. Several other analogous facts were mentioned, and the sugges- 
tion made, that the whole were probably the result of an inductive 
action in the long wire, similar to that observed in a long galvanic 
current : the subject now required further investigation. 
Professor Henry concluded by observing, that the facts he had 
given in this communication were such as must have been noticed 
by every person who is in the habit of experimenting on ordinary 
electricity ; but he believed these had never been studied in this con- 
nexion. He was anxious to direct the attention of the Section to the 
subject, as one which appeared to afford an interesting field of re- 
search, particularly in connexion with the recent discoveries of the 
surprising inductive actions of galvanic currents. 
On a convenient and efficient form of Electro-magnetic Apparatus for 
the production of Electricity of high Intensity. By Rrv. J. W. 
M‘Gautey, Professor of Natural Philosophy to the National Board 
of Education in Ireland. 
He remarked that, although he had not altered his opinions on 
the applicability of Electro-magnetism as a moving power, he con- 
ceived we ought not to be satisfied with almost any portion of our 
present electro-magnetic apparatus; but that all that an individual 
