By invitation of a well-known official, I visited the Navy-Yard yesterday, and witnessed the trial of some newly-invented rifled cannon. The trial was of short duration, and the jury brought in a verdict of “innocent of any intent to kill.”

The first gun tried was similar to those used in the Revolution, except that it had a larger touch-hole, and the carriage was painted green, instead of blue. This novel and ingenious weapon was pointed at a target about sixty yards distant. It didn’t hit it, and as nobody saw any ball, there was much perplexity expressed. A midshipman did say that he thought the ball must have run out of the touch-hole when they loaded up, for which he was instantly expelled from the service. After a long search without finding the ball, there was some thought of summoning the Naval Retiring Board to decide on the matter, when somebody happened to look into the mouth of the cannon, and discovered that the ball hadn’t gone out at all. The inventor said this would happen sometimes, especially if you didn’t put a brick over the touch-hole when you fired the gun. The, Government was so pleased with this explanation, that it ordered forty of the guns on the spot, at two hundred thousand dollars apiece. The guns to be furnished as soon as the war is over.

The next weapon tried was Jink’s double back-action revolving cannon for ferry-boats. It consists of a heavy bronze tube, revolving on a pivot, with both ends open, and a touch-hole in the middle. While one gunner puts a load in at one end, another puts in a load at the other end, and one touch-hole serves for both. Upon applying the match, the gun is whirled swiftly round on a pivot, and both balls fly out in circles, causing great slaughter on both sides. This terrible engine was aimed at the target with great accuracy; but as the gunner has a large family dependent. on him for support, he refused to apply the match. The Government was satisfied without firing, and ordered six of the guns at a million of dollars apiece. The guns to be furnished in time for our next war.

The last weapon subjected to trial was a mountain howitzer of a new pattern. The inventor explained that its great advantage was, that it required no powder. In battle it is placed on the top of a high mountain, and a ball slipped loosely into it. As the enemy passes the foot of the mountain, the gunner in charge tips over the howitzer, and the ball rolls down the side of the mountain into the midst of the doomed foe. The range of this terrible weapon depends greatly on the height of the mountain and the distance to its base. The Government ordered forty of these mountain howitzers at a hundred thousand dollars apiece, to be planted on the first mountains discovered in the enemy’s country.

These are great times for gunsmiths, my boy; and if you find any old cannon around the junk-shops, just send them along.

There is much sensation in nautical circles arising from the immoral conduct of the rebel privateers; but public feeling has been somewhat easier since the invention of a craft for capturing the pirates, by an ingenious Connecticut chap. Yesterday he exhibited a small model of it at a cabinet meeting, and explained it thus:

“You will perceive,” says he to the President, “that the machine itself will only be four times the size of the Great Eastern, and need not cost over a few millions of dollars. I have only got to discover one thing before I can make it perfect. You will observe that it has a steam-engine on board. This engine works a pair of immense iron clamps, which are let, down into the water from the extreme end of a very lengthy horizontal spar. Upon approaching the pirate, the captain orders the engineer to put on steam. Instantly the clamps descend from the end of the spar and clutch the privateer athwartships. Then the engine is reversed, the privateer is lifted bodily out of the water, the spar swings around over the deck, and the pirate ship is let down into the hold by the run. Then shut your hatches, and you have ship and pirates safe and sound.”

The President’s gothic features lighted up beautifully at the words of the great inventor; but in a moment they assumed an expression of doubt, and says he:

“But how are you going to manage, if the privateer fires upon you while you are doing this?”

“My dear sir,” says the inventor, “I told you I had only one thing to discover before I could make the machine perfect, and that’s it.”

So you see, my boy, there’s a prospect of our doing something on the ocean next century, and there’s only one thing in the way of our taking in pirates by the cargo.

Last evening a new brigadier-general, aged ninety-four years, made a speech to Regiment Five, Mackerel Brigade, and then furnished each man with a lead-pencil. He said that, as the Government was disappointed about receiving some provisions it had ordered for the troops, those pencils were intended to enable them to draw their rations as usual; I got a very big pencil, my boy, and have lived on a sheet of paper ever since.

Yours, pensively,

ORPHEUS C. KERR.