WHEN internal combustion engines can drive anything from a liner to a wheel-chair; when they can carry an aeroplane miles above the earth's surface, and propel a car along it at speeds approaching two hundred miles an hour-there does not seem to be room for very extensive improvement in its achievement. Yet from the scientific point of view much remains to be done in the way of perfecting the efficiency of the engine and raising the ratio of power obtained to heat supplied. Professor Burstall will examine possible lines of advance in this evening's talk.