In this new material one mystic formula, or rather pair of formulae, recurred so often that Willett had it by heart before he had half finished his quest. It consisted of two parallel columns, the left-hand one surmounted by the archaic symbol called "Dragon's Head" and used in almanacks to indicate the ascending node, and the right-hand one headed by a corresponding sign of "Dragon's Tail" or descending node. The appearance of the whole was something like this, and almost unconsciously the doctor realised that the second half was no more than the first written syllabically backward with the exception of