TRANSACTIONS OF THE SECTIONS. 31 
The mode adopted iv these researches of finding the height of waves, is, I believe, 
quite satisfactory, and, observed with care and with relation to numbers or propor- 
tion of waves, as accurate as need be. The depression of the horizon in respect to 
the elevation of the observer is too small to form even a correction. As the horizon 
from the paddle-box, S=15 feet, had only a depression of 3! 49", the distance of 
the visible horizon, as seen from this elevation, would be 4°45 statute miles, and the 
actual depression in feet due to the distance of the summit of the wave when the 
ship was in the midst of the hollow, could only be 0°18 foot or 2°16 inches. 
Other modes of determining the width of a wave, or the extent betwixt summit 
and summit, much preferable to that described (the only available one I could de- 
vise), might easily be adopted where the management of the ship was in the hands 
of the observer. In steam ships, the simplest mode for high seas, perhaps, would 
be altering the speed of the ship when going in the direction of the wave or against 
the wave; the ratios of the times of transit of wave-crests under different rates of 
sailing of the ship might yield very close results to the truth. 
In moderate-sized waves, the plan adopted by Captain Stanley, whose observa- 
tions I did not meet with before this meeting, seems satisfactory. But in calms or 
moderate weather, after a storm, that is for the determination of the velocities of 
less elevated waves, a variety of processes might be available. 
The author referred, in conclusion, to the waves near shore, the effect of shallow 
water — waves entering narrow channels betwixt smooth shelving shores, different 
from waves entering betwixt rocky (pointed) sides, such as Brassa ‘Sound. 
On Cometary Physics. By Prof. Suytu, F.R.S.E. 
Account of the Edinburgh Observatory. By Prof. Smyru, F.RS.E, 
METEOROLOGY. 
On the Attempts to resolve the Pressure of the Atmosphere into two parts, that 
of Vapour and Dry Air. By J. A. Broun, F.R.S.E. 
On some extraordinary Electrical Appearances observed at Manchester on 
the 16th of July 1850. By Peter Crarsz, F.R.AS. §e. 
About four o’clock p.m., on the 16th of July, the weather having been fine and 
warm for four days, the wind blowing from the north-east, and the clouds constantly 
moving from the east, some dense clouds appeared in the east, north, and also to the 
west, when one or two peals of thunder were heard at a distance. About this time 
a violent storm of thunder, lightning and very heavy rain commenced at Bolton, 
twelve miles N.N.W. of Manchester, extending westward and to the W.S.W. for 
many miles, and continued for two or three hours. 
Afterwards the clouds extended to the south-west and south, and distant thunder 
was heard over a considerable extent of country to the south-west of Manchester, 
for several hours. 
About nine o’clock, the clouds being very dark to the west and south-west of 
Manchester, but not so dense to the south and south-east, very frequent flashes of 
sheet lightning were observed, whilst for a period of nearly half an hour there were 
frequent coruscations of lightning observed between the south and south-west, all 
moving in a direction from south-west towards south, at an elevation of from 14°to 20° 
above the horizon ; sometimes the appearances were like the roots of a tree, and oc- 
casionally with bright balls at the termination of all or some of the branches. On 
several occasions, immediately after a stream of light seemed to pass from near the 
south-west towards the south, through a space of 10° or 12°, a luminous ball of 
considerable size suddenly appeared and moved along the line of the stream with a 
velocity so slow that its progress was easily observed, and this was repeated several 
times near the same place. 
