ADDRESS. 21 



At first siglit one would be tempted to say that the density of the air 

 on the underside of a shot must, notwithstanding its motion of descent, 

 be so nearly the same as that of the air upon the upper side as to cause the 

 difference to be unworthy of consideration ; but we know that the projectiles 

 from rifled guns tend to travel sideways as they pass through the air, and 

 that the direction of their motion, whether to the right or to the left, de- 

 pends on the ' hand ' of the rifling. We know also, that the friction against 

 liquid or against gaseous bodies varies with the densities of these bodies, 

 and it is believed that, minute as is the difference in density to which I have 

 referred, it is suSicient to determine the lateral movement of the 

 projectile. This lateral tendency must be allowed for, in these days of 

 long ranges, in the sighting and laying of guns, if we desire accuracy of 

 aim, at those distances at which it is to be expected our naval 

 engagements will have to be commenced, and perhaps concluded. We 

 can no longer afford to treat the subject as Nelson is said to have treated 

 it, in one of his letters to the Secretary of the Admiralty, who had 

 requested that an invention for laying guns more accurately should be 

 tried. Nelson said he would be glad to try the invention, but that, as 

 his mode of fighting consisted in placing his ship close alongside that of 

 the enemy, he did not think the invention, even if it were successful, 

 would be of much use to him. 



While upon the question of guns, I am tempted to remark upon that 

 which is by no means a small thing (for it is no less than the rotation 

 of the earth), which in long-distance firing may demand attention, and 

 that to an extent little suspected by the civilian. 



Place the gun north and south, say in the latitude of London, and fire 

 a 12-mile round such as I have mentioned, and it will be found that, 

 assuming the shot were passing through a vacuum, a lateral allowance of 

 more than 200 feet must be made to compensate for the different velocity 

 of the circumference of the earth at 12 miles north or south of the place 

 where the gun was fired, as compared with the velocity of the circum- 

 ference of the earth at that place itself — the time of flight being in round 

 numbers one minute. 



At the risk of exciting a smile, I am about to assert that engineering 

 has even its poetical side. I will ask you to consider with me whether 

 there may not be true poetry in the feelings of the engineer who 

 solves a problem such as this : Consider this rock, never visible 

 above the surface of the tide, but making its presence known by the 

 waves which rise around it : it has been the cause of destruction to many 

 a noble vessel which had completed, in safety, its thoasands of leagues 

 of journey, and was, within a few score miles of port ; then dashed to pieces 

 upon it ? Here is this rock. On it build a lighthouse. Lay your founda- 

 tions through the water, in the midst of the turmoil of the sea ; make 

 your preparations ; appear to be attaining success, and find the elements 

 ure against you and that the whole of your preliminary works are ruined 



