In his book, published in 1892, Grey used the same metaphor that Jordan used in her book, which was published in 1885. The metaphor is so unusual that there is little chance that two different people independently created it. Ttherefore, it is highly likely that Grey read Jordan' s book.
A text that was probably known to both Jordan and Grey was published in 1860 and also contained the same unusual metaphor most weakens the argument.