Although we have no guide to Mary Shelley's thought processes as she wrote this passage,
it is probable that the stanza from Percy Shelley's poetry she quotes at the end of
the paragraph caused her to think of another from the volume in which it was published
(or the causality might have been reversed, with that other passage first coming to
mind and prompting the remembrance of this stanza): whatever the case, this description
of mountain conifers strongly resembles the desolate final scene, actually drawn from
Shelley's experiences in Wales before he met Mary, of his poem "Alastor" (see lines
550-70). An early sketch of this same subject is contained in a poem in the early
notebook known as the Esdaile Notebook, a poem Shelley wrote in 1811 and never published,
called after its first line "Dark spirit of the desart rude."
On the other hand, the scenery of Switzerland, far more sublime than that of Wales,
afforded ample opportunity for Mary Shelley to observe the desolation that alpine
storms and glacial movement could visit on the pine forests of the mountains. There
is a description of such shattered trees in Letter 4 of A History of Six Weeks' Tour.
Byron offers another such passage in the second scene of Manfred, I.ii.66-74, which,
though begun later than Frankenstein, indicates at many points a common conceptual
origin.