TRANSACTIONS OF THE SECTIONS. 189 
at the muzzle, and the object aimed at; and these three being at very unequal di- 
stances from the eye, cannot be seen all equally distinct at the same time. 
2nd. Unless the barrel is of inordinate length, there is not sufficient radial length 
between the sights to give the opportunity of pointing accurately. 
3rd. As only one of the breech-vanes can be raised at a time, there are no means 
of making allowance for distances intermediate between those for which the vanes 
are calculated. 
4th. In sunshine there is a phase of the muzzle-sight which is very prejudicial to 
correct aiming. 
All these difficulties may, however, be got over, by applying to the barrel a small 
telescope with cross wires, for— 
Ist. There are only ¢wo objects to deal with, the cross wires and the image of the 
object aimed at, and these are both at precisely the same distance from the eye. 
2nd. The accuracy of pointing depending on the magnifying power of the tele- 
scope, the shortest barrel may be made equal to the longest. 
3rd. The whole system of wires being in view at once, afford a very convenient 
scale for the intermediate distances. 
4th. The wires being in the tube of the telescope, can be affected by no phase from 
sunshine. 
A convenient size of telescope is about 1 foot long, including a direct eyepiece ; 
the aperture of the object-glass being 3 inch. 
The author exhibited a small rifle to which he had applied the telescope sights six 
years ago; but stated that he had lately found that he had been preceded by Capt. 
D. Davidson, Bombay Army, at present in Scotland, who had moreover carried the 
subject much further, and had had several telescopes made and applied to various 
rifles by Mr. Adie, optician, and Mr. Dickson, gunmaker of this city. 
The author likewise took this opportunity of mentioning that the introduction of 
the sugar-loaf ball was due to Capt. D. Davidson, as it seemed to be another in- 
stance of the propriety of taking into account the resistance of the air; a matter, 
the neglect of which, in the simple motion of projectiles, had so utterly confounded 
all the results of theory, that until Robins at last took it into account, we cannot 
say that anything was known of gunnery. 
But Robins computed, and many others have done 50 since his day, that if a ball 
be made long and heavier at one end than the other, the heavier end will always go 
foremost; accordingly egg-shaped and sugar-loafed and conical balls were fired out 
of rifles and smooth bores with the expectation of their going much straighter than 
spherical ones; but they went far worse, and tumbled over and over, instead of 
having the thicker end always first. 
At length Capt. Davidson tried one of them with the point foremost, and it went 
perfectly straight, with the point first at all distances; and sugar-loafed balls fired 
point first are now not only used extensively in this country, but are coming into 
use on the continent also. 
The reason of theory being apparently at fault here, seems to be that the greater 
resistance of the air to the larger end of the ball overbalances the advantage due 
merely to its superior weight. 
Observations on the Force of the Waves. 
By Tuomas Srevenson, F.R.S.E., Civil Engineer. 
The author, after some introductory remarks, described the action of the marine 
dynamometer, the self-registering instrument with which the observations were 
made, and one of the instruments was exhibited. He stated that a theoretical ob- 
jection might perhaps be started to referring the action of the sea to a statical value; 
but contended that in designing sea-works the attempt of the engineer is to oppose 
the dynamical action of the sea by the dead weight or inertia of the masonry, so that 
the indications of the marine dynamometer furnish exactly the kind of information 
which the engineer requires. The greatest result registered in the Atlantic Ocean 
was at Skerryvore during the westerly gale of the 29th of March, 1845, when the 
force was 6083 105., or 3 tons per square foot. The greatest result registered in the 
German Ocean was 3013 lbs., or about 14 ton per square foot. It further appeared, 
from taking an average result for five of the summer months during the years 1843 
