Within the last twenty-five years, and more especially since the Franco-German war, when the French made such good use of balloons, there have been somewhat frequent rumours that the problem of aërial navigation, comprised in the possibility of guiding and propelling a balloon in a given direction, had been solved. The machine in each case is carefully described, and generally it is represented as having risen gracefully in the air, travelled about a little, and then returned to its starting-point. Then, nothing more is heard of it. Such an event is said to have occurred last month in France. The gas-vessel—it can hardly be called a balloon, for it is cigar-shaped—is nearly two hundred feet long. A platform is hung below, upon which is a screw propeller, worked by a dynamo-machine and a large rudder. This description tallies almost exactly with the form of so-called steerable balloons which have been constructed, tried, and found useless by M. Giffard, M. Tissandier, and others in previous years. The French government have spent much money in experimental ballooning, and this last achievement is the result. Perhaps the authorities were obliged to show something for the money that was being spent, but we fear that that something is not anything new or profitable. Until an aërial machine be produced which shall make its way _against_ strong currents, balloon navigation will remain as it has hitherto been. Here is a clever American notion, and one which will probably have a wide application. It consists of a noiseless door-closer. In the ordinary metal or india-rubber spring, so commonly fixed to doors, the greatest energy is exerted at first, and the door generally slams with a noise which is very distressing to any one with nerves. In the new arrangement, the spring is fixed to the piston attached to a small air-cylinder, so that as the door closes, the resistance of the air in the cylinder checks its motion before the terrible bang arrives. A small opening in the cylinder then lets in the air, so that the spring once more asserts its authority with sufficient persuasion to gently close the door.