The last application of rock-oil is a petroleum engine, which we saw working lately in London. In general appearance, it is like a gas engine; but it has a tank fixed above the cylinder which contains a supply of petroleum. This liquid is conveyed by a small pipe and pump to the cylinder at the rate of about four drops per stroke of the piston rod. It is ignited by a spirit-lamp after having been mingled with sufficient air to form an explosive mixture. The working cost of the engine is calculated at three-halfpence per horse-power per hour for petroleum, and one-sixth of that sum for lubricating. The engine will be valuable where gas is not to be obtained and where steam is inadmissible. Mr William Anderson lately delivered an interesting lecture before the Royal Institution ‘On New Applications of the Mechanical Properties of Cork to the Arts.’ He showed that cork was unique among solid substances in being capable of cubical compression both from forces applied in opposite directions and from pressure from all sides. This is shown when cork is immersed in water and is subjected to hydraulic pressure. The phenomenon in question is due to the peculiar cellular structure of the material, which causes it to behave more like a gas when under pressure than like a solid. Mr Anderson proposes to use cork instead of air in the air-vessels of water-raising machinery, and he showed by experiment how well fitted it was for doing this duty. He also proposes to use it in connection with gun-carriages in the following way: the carriage is to be furnished with hydraulic compressors in the customary manner, but the water in the cylinders is to be driven by the recoil of the gun into a vessel filled with cork. This will represent a store of energy which will run the gun out again when loaded, by the aid of a tap which will liberate the water from the compressed cork. The lecture certainly exhibited cork in a new character, and called attention to many ways in which it can be used with advantage. The nebula in the Pleiades, so strangely discovered by photography, although it was quite invisible to ordinary telescopic scrutiny, has now been detected by more than one observer. It is, however, as may be guessed, an extremely faint object. MM. Perrotin and Thollon, of the observatory at Nice, say that they have seen it, but admit at the same time that this was only because they knew from the Paris photograph that it existed.