... the Consul remembers a make of golfball called the Zodiac Zone, a lot more evidence in [Chapter] XI. ... The scorpion is an image of suicide: (Scorpions sting themselves to death) .... I now see the whole book takes place "in Scorpio" ... the action of the book is one day, exactly 12 hours, seven to seven; the first chapter takes place 12 months later on the same day, so, is also in Scorpio... Malcolm Lowry, Letters.
Under the Volcano gives numbers a great significance. In particular, the number seven, branded on the horse that kills Yvonne, stands out, also representing the Pleiades cluster to which Yvonne feels herself rising upon her death. [The Pleiades are also known as the Seven Sisters, derived from the Greek myth which names the brightest seven stars in the cluster the daughters of the titan Atlas and the sea-nymph Pleione.]
(Interestingly, given the Consul's constant struggle with alcohol, the Pleiades along with the seven Hyades were nursemaids and teachers to the infant Bacchus, or Dionysus, god of wine.)
Below: The Pleiades in a colour-composite image, courtesy NASA / ESA / AURA / Caltech
Here, 1 + 8 = 9, a number which would not be of special significance had not Lowry changed, on p. 17 his original 366 churches to 306 (3 + 6 = 9), for esoteric reasons only partially clarified by Aleister Crowley's The Sword of Song, p. 10: "TRINITY OF TRIADS with MALKUTH pendant to them, manifesting their influence in the Material Universe" (that is, Nine is the number of Sephiroth, or emanations from the godhead, on the Cabbalistic tree of life above Malkuth, the kingdom or material universe.
Also, 5 + 7 = 12, the number of chapters in the novel, but the number 57 is also a remnant of a cross-reference deleted from the final version: in the short story version of the novel, the Consul was going to drown his remorse by having "fifty-seven drinks at the earliest opportunity." There is also the invincible Tomás Aguero (Sp. "omen of drink"?), who weighs 57 kilos and appears (by coincidence) on p. 57. In 1939, 57 would be an everyday reminder of the 57 varieties of Heinz, and Lowry undoubtedly intended a provate allusion to Aiken's Blue Voyage, where this is cited in the context of one who is a dabbler in black arts and all known perversions: "the fifty-seven varieties were child's play to me."
As Lowry would have known from Lewis Spence, the number 400, in the phrase "four hundred rabbits," was among the Aztecs a figure of total drunkenness, an offence punishable by death.
Perle Epstein writes that Lowry's preoccupation with numbers was stimulated by the works of Frater Achad.