In the development of war material it has more than once happened that weapons of destruction have shown that they can be quite as harmful to friend as to foe. A notable instance of this is found in the destructive effects which the larger pieces of artillery mounted UJlon warships sometimes exercise upon the vessels themselves. It is not an uncommon experience (though not so frequent of late years as it was a decade or two ago) for a new warship to return from her gun trials with a large proportion of her gun mounts so badly racked and loosened up by the recoil as to need a thorough readjustment, if not the design of new mountings and attachments. Equally, if not even more destructive has been the effect of the blast at the muzzle, where the impact of the expanding gases has proved sufficient to wreck superstructures, and bodily force down a large area of the deck of the ship. A recent instance of these destructive effects is recorded in Cosmos as having occurred in the Italian navy upon the old battleship "Morosini," now desig nated as a coast-defense vessel. The "Morosini" is one of the early battleships, upon which were mounted the huge 17:)Hnch 100-ton guns, manufactured by Armstrong, which created such a furor over two decades ago. According to our contemporary, the question had arisen as to what would be the effect upon the ship and crew of the simultaneous discharge of these four huge pieces; and it was resolved to put the matter to a thorough test. The "Morosini" carries her four guns in two turrets arranged en eche16n, or diagonally, on the main deck amidships. Each one was loaded with a charge of about 770 pounds of powder, and at a given signal the four guns were discharged simultaneously, and the effects of the explosion of over 3.000 pounds of powder noted. The results as given by our contemporary must, we think, have been samewhat exaggerated, or else the guns had never be- fore been fired with fllll charges. It is stated that there was considerable dislocation of the armor, rivets being started as by the pressure of an interior explosion, and that parts vf the machinery were rendered inoperative. We think it is more than likely that this damage must have referred to that portion of the deck located below the muzzles of those guns which were trained across tUe deck. In this connection it is interesting to bear in mind that the three large cruisers of the "Invincible" type, which are being completed for the British navy, have four of their guns arranged to train across the deck. We understand that in rein-troducing this system, special attention is being given to the strengthening of the deck and such portions of the ship as will be exposed to the impact of the gases. The Armstrong guns, referred to above, were built in the days of the old quick-burning powder, which gave a high breech pressure but low muzzle pressure. In these days of smokeless powder, where the muzzle llressures are high, the racking effects of "blast" are proportionately more severe, and call for special structural strength in the parts of the ship that may be affected.