Your automobile's differential is easily one of its most important components. This becomes crystal clear to anyone that has ever had to pony up to replace one. The differential, that mathy-driven, mechanically complex system that keeps axles and pinions running smoothly was invented by a watchmaker - for a watch.

Question: Could you explain what is meant by "horological gearing"? I never heard of this before, although I understand it has something to do with watches. Could you also explain the meaning of a "going gear train"?