256 
Proceedings of the Royal Society 
To take a particular example, let ^ = 1000 feet a second, and let 
p = the density of water, so that 
p=ghp 
when h is the height of the column of water producing an equal 
pressure — 
ghp = pv* 
If w be the weight of a cubic foot of water, p = ivh = w— is the 
g 
pressure on the square foot. 
Now, w— 72 lbs. and g = 32 and v 2 = 1,000,000 ; 
79 
p = -^x 1,000,000 lbs. on the square foot ; 
Or, 144 — 2240 X ^2 X tons on s 4 uare i nc h 
= 7 tons on the square inch. 
A pressure which the muzzle of a shot gun is not constructed to 
withstand, and the theory shows that this great pressure can be pro- 
duced even by a plug of snow or grease of the shortest length ! 
movable inside the barrel with the greatest facility. If the velocity 
of the ball or wad be less than that of sound the snow-plug is not 
driven out quite suddenly, and if the velocity be small enough the 
snow-plug is driven out before the ball or wad reaches the muzzle. 
5. On some New Bases of the Leucoline Series. Part III. 
By G. Carr Bobinson and W. L. Goodwin. 
Monday , 7 th July 1879. 
Professor MACLAGAN, Vice-President, in the Chair. 
The following Communications were read : — 
1. Notice of Striated Rocks in East Lothian and in some 
adjoining Counties. By David Milne Home, LL.D. 
I know no more interesting problem in geology than the ques- 
tion, What was the great agency which brought the surface of 
