‘To a Wreath of Snow’ shows Emily Brontë (1818-48), some ten years before the publication of her sole novel Wuthering Heights (1847). Written when she was still a teenager, ‘To a Wreath of Snow’ deserves some words of analysis to illuminate the language and imagery Brontë so deftly uses in what might be described as a late Romantic poem.
To a Wreath of Snow
O transient voyager of heaven!
O silent sign of winter skies!
What adverse wind thy sail has driven
To dungeons where a prisoner lies?
Methinks the hands that shut the sun
So sternly from this mourning brow
Might still their rebel task have done
And checked a thing so frail as thou
They would have done it had they known
The talisman that dwelt in thee,
For all the suns that ever shone
Have never been so kind to me!
For many a week, and many a day
My heart was weighed with sinking gloom
When morning rose in mourning grey
And faintly lit my prison room
But angel like, when I awoke,
Thy silvery form so soft and fair
Shining through darkness, sweetly spoke
Of cloudy skies and mountains bare
The dearest to a mountaineer
Who, all life long has loved the snow
That crowned her native summits drear,
Better, than greenest plains below –
And voiceless, soulless messenger
Thy presence waked a thrilling tone
That comforts me while thou art here
And will sustain when thou art gone
Emily Brontë wrote ‘To a Wreath of Snow’ in December 1837, when Emily’s sister Anne fell ill at Roe Head school and had to be withdrawn by her sister Charlotte, who was teaching there. Emily was just 19 years old when she wrote ‘To a Wreath of Snow’, but she was clearly already in full control of her gifts.
The poem had its roots in the Brontës’ childhood, and their creation of fantasy worlds based on the brother Branwell Brontë’s tin soldiers. 
Each sibling was given a toy soldier and created a life for him. A split opened up between the siblings, with Emily and Anne pairing up to create Gondal, a fairy-tale land inspired by the rugged, brooding landscape of Yorkshire they knew so well.
‘To a Wreath of Snow’ is actually written in the voice of an invented character from this fictional world of Gondal. The speaker is not Emily herself, but Augusta Almeda, the Queen of Gondal. Gondal was a fantasy world created by Emily and Anne three years previously. Augusta Almeda is in a prison cell and looking out at the snow outside, wishing herself elsewhere.
The speaker apostrophises this ‘wreath of snow’ as she sees it from the window of her prison cell: that is, she addresses the snow, in rhetorical terms. It is a ‘transient voyager of heaven’ because the snow will soon melt; Almeda is capturing passing beauty. Although the snow is cold and the sun is warm and bright, Almeda finds this ‘wreath of snow’ far more comforting and, indeed, heartening to her in her state of mourning than she does the sunshine. There’s a bit of pathetic fallacy going on: the fact that she describes it as a wreath of snow suggests funeral wreaths and mourning, a word that the speaker uses more than once about herself. The snow reflects the speaker’s mood far more closely than the glaring sun, which merely heralds another day trapped within her prison cell. She identifies with the snow and its transience perhaps reminds her of the brevity of her own life – and of all life.
The snow also reminds her of the beauty of snow-capped mountains, which she admires, as the next stanzas highlight. The snow is ‘voiceless’ and ‘soulless’: the worth of nature is that it is resolutely not human, but instead reminds the speaker of the landscapes of mountains and snow. Although she is solitary in her prison cell, she doesn’t pine for human contact, but it’s the natural world that she misses, rather than other people, such as a beloved or her family. (Where’s the King of Gondal in all this, one wonders? Or did Almeda’s imprisonment precede her accession to the throne of that fictional land?) The poem is decidedly Romantic: it’s about the individual’s relationship with nature.
‘To a Wreath of Snow’ is written in quatrains rhymed abab (alternating rhyme), in iambic tetrameter. There is, however, the odd trochaic substitution, as in the third line of this stanza:
But angel like, when I awoke,
Thy silvery form so soft and fair
Shining through darkness, sweetly spoke
Of cloudy skies and mountains bare
A trochee (‘TUM-ti’, e.g. as in the word ‘Shining’) is the opposite of an iamb (‘ti-TUM’, e.g. as in the word ‘awoke’): in a trochee, the first syllable rather than the second is stressed. This means that we get a strong, forceful opening to the line describing the snow ‘Shining through darkness’: the disruption to the usual metrical pattern mirrors the welcome arrival of the bright snow.