78 ANNUAL OF SCIENTIFIC DISCOVERY. 



drical heads countersunk into the plating and flush with the outside. 

 Several of these screw-bolts have been struck directly on the head with- 

 out causing any damage ; whereas, if the ordinary plan of using through 

 bolts or rivets had been adopted, it is very probable that some persons 

 would have been injured by fragments of the bolts being projected 

 inside the ship. In the case of the monitors, the most serious acci- 

 dents that have occurred on board them have arisen from the displace- 

 ment and breaking of the bolts that hold together the plates of their 

 turrets, through the impact of heavy shot. An idea of the fighting 

 capabilities of the Ironsides may be formed from the circumstance that 

 she threw, in the various attacks in which she participated from April 

 to September, upwards of 4,400 shells. 



It is understood that one result of the attack on the fortifications of 

 Charleston, by the U. S. iron-clad fleet, has been the withdrawal from 

 the monitors of the fifteen-inch guns, with which their turrets were 

 armed, and the substitution of thirteen-inch guns in place. 



New Port-Closer for Vessels of War. An ingenious device for 

 closing the ports of iron-clads and other vessels of war has recently 

 been patented by Mr. W. S. Auchincloss, of New York City. The 

 nature of the invention will be readily understood from the following 

 clause of the patent : The employment or use for a port-hole closer 

 of two rollers, each being made to rotate independently of the other, 

 and provided with a cavity, so that by turning the rollers to the proper 

 position an opening is obtained which allows of giving to the gun any- 

 desired elevation, or of training the same to an angle of 45 or more. 



