William S. Davis observes that Shelley's ideal island is "a place without gaps or fissures of any kind, another 'fantasy of untouchable fullness.' The poet is careful to point out to Emily that there are no empty spaces here, even at the atomic level, as is filled by the smile of the 'Soul' that 'burns at the heart' of the island--a smile we feel but do not see, 'O'er the gray rocks, blue waves and forests green, / Filling their bare and void interstice' [...]. The aqueous soul of the island [...] is able to fill all fissures and cracks because it is itself not limited by material boundaries" (63).
Davis, William S. "Living Landscapes: Schelling, Goethe, Shelley." 2002. 49-71.