The sun line, also called the line of Apollo, runs vertically toward the ring finger, and the tradition reads it for reputation, artistic capacity, public recognition and good fortune; like the fate line it is absent in many hands, and its presence is read favourably. The naming again borrows the astrological significations of the Sun. Palmistry belongs to a family of divinatory arts that read the body, alongside physiognomy, phrenology and metoposcopy, the reading of the lines of the forehead, and of these it is the only one still widely practised. Phrenology, its nineteenth-century sibling, is now the standard textbook example of a discredited science, and the comparison is instructive: both were systematic, both attracted serious adherents, and both failed for the same reason, that their claimed correspondences did not hold when tested.
India's samudrika shastra gives the line its own name, surya rekha, and some texts also call it yasha rekha, the line of fame, an association with recognition that matches the Western reading. Cheiro himself used Line of Apollo and Line of Brilliancy as alternative names for what other writers of his period simply called the Sun line, following the Greek attribution of the mount beneath the ring finger to Apollo rather than to the Sun itself. Multiple lines running parallel are read by some schools as an indication of several talents or interests rather than as intensifying a single one, one more instance of the ambiguity that runs through the whole art.
Sources Les Mysteres de la MainAdolphe Desbarrolles with Palmistry for AllCheiro (William John Warner)