224 < 
Royal Irish Acadeiny, 
having formed on the top of a large cross of common crystals, 
they must have been generated under circumstances either on a 
lower temperature or a less concentrated solution than that 
by which the common variety is produced. If the new- 
formed cr^^stals be dissolved in water, it is under the ordinary 
form that they recrystallize. 
When iodide of potassium is crystallized in leaden or tinned 
iron vessels, Mr. Scanlan has informed me that the crystalline 
form is altered, from the presence of a minute quantity of 
iodide of tin or lead ; but what the alteration is exactly, I do 
not believe has been determined. Having heard the fact, 
however, from my friend Mr. Scanlan, I sought for metallic 
impurity in the crystals now described, but in vain. They are 
chemically pure. 
XLII. Proceedings of Learned Societies, 
ROYAL IRISH ACADEMY. 
Nov. 11, EV. Dr. Dickinson gave a verbal account of a remark* 
1839. able waterspout, which he had observed at Killiney 
during the last summer. 
Towards the end of the month of July, about 10 a. m., while 
standing on the shore of the bay of Killiney, his attention was di- 
rected by a friend to a waterspout, distant about a quarter of a mile 
from the land. It was not similar in form to the representations of 
waterspouts usually given, and may therefore deserve to be noticed. 
It was shaped like a double siphon, the whole being suspended at 
a considerable elevation in the air ; the longer end of the siphon 
reached towards the sea, and appeared to approach it nearer and 
nearer, till, at length, its waters were distinctly seen rushing into 
the deep. The loop gradually lowered, as if sinking and lengthen- 
ing by its own weight, while the upper part of the siphon seemed 
not to lose in elevation. At length the loop burst, and there were 
three streams of water pouring into the sea, two of those streams 
still continuing united by the arch at the top. I'he breadth of these 
streams gradually diminished till they became invisible, but their 
length seemed undiminished as long as they were at all seen. The 
quantity of water poured down must have been very considerable, 
as the bubbling of the sea beneath could be distinctly observed. 
Dr. Dickinson was informed that a waterspout fell a few days 
after inland, towards the Three-Rock mountain. It is said to have 
done some injury ; but his informant did not see it, and he could 
not, therefore, ascertain its shape. 
November 30, 1839. Mr. Clarke read a paper ‘‘ On Atmospheric 
Electricity.” 
The author commenced his paper with a description of the appa- 
ratus which he had employed in the experimental investigation of 
this subject. He showed the inapplicability of the electrometers 
