TRANSACTIONS. 
85 
the air-pump would lead us to conclude that electricity would 
pervade an actual vacuum without sensible resistance, and 
without exhibiting light. But Mr. Walsh, Mr. Morgan, and 
other experimenters, had asserted that electricity could not 
pervade a perfect Torricellian vacuum. Sir Humphry Davy 
has maintained that the Torricellian vacuum is permeable to 
electricity, with an exhibition of more or less light according 
to the temperature. But as the appearances he describes are 
similar to those given by Mr. Morgan, when a very minute 
portion of air remained in his tube, it must be considered a 
question still open to further investigation. 
From the writer’s experiments, made with the object of 
learning something which might throw a light on the nature of 
Aurora Borealis, it has appeared, in conformity with the pre¬ 
vious experiments of Sir Humphry Davy, Mr. Morgan, and 
others, that the passage of electricity through space containing 
only a very minute portion of air, was attended with a very 
considerable display of light, and this when the mercury in the 
tube stood scarcely perceptibly lower than that in a good 
barometer. 
Dr. Warwick exhibited the method of making a powerful 
temporary Magnet, by coiling round a liorse-slioe of soft iron 
a quantity of copper wire, connecting the poles of a galvanic 
battery, as originally performed by Professor Moll of Utrecht. 
Dr. Daubeny exhibited a new instrument composed of 
finely reticulated wire, intended to illustrate the effects of 
capillary attraction. 
A description of the New Volcanic Island, by Mr. Osborn, 
communicated by Captain Hotham, R.N., was read to the 
Meeting. 
SATURDAY MORNING. 
Mr. Dalton, President of the Manchester Society, read his 
Physiological Investigations arising from a consideration of 
the mechanical effects of atmospheric pressure on the a?iimal 
frame. 
In this essay Mr. Dalton endeavours to answer the question, 
how the animal body is enabled to resist the pressure of the 
external atmosphere, which varies in amount from 15 to 20 
tons on a middle-sized man, without being sensible of the whole 
or any part of this enormous and fluctuating pressure. 
The average specific gravity of the human body being taken 
