I can't figure out the vocabulary and imagery of "The Darkling Thrush." Please help.
The vocabulary and imagery of the poem are directed mainly toward creating a sense of the bleakness and sadness of the winter landscape. For example, the "Frost" is described as "specter-gray." How else does Hardy's language give to the wintry scene, a dreariness that is more than just visual or physical?
In the first stanza of "The Darkling Thrush," the "dregs" are the least valuable part of something, the sediment or grounds left at the bottom of a liquid. A common phrase is "the dregs of society" which means the criminal element, the worst of the worst. In this first stanza, the dregs of winter are the most desolate aspects of a winter scene: frost, grey skies, cold wind, bare trees, etc. The simile of the tangled bine-stems (shrub branches) and the broken strings of a lyre add an audible sense of disharmony.
The second stanza compares the deathly scene to a funeral for the closing 19th century. The poem was published in 1901. In lines 13-16, the speaker notes that the usually inevitable transition from winter to spring (and the analogous transition from the 19th to the 20th century) seems less likely because of how desolate things appear. The analogy with the close of the century supposes a lack of hope for the next century.
The ancient pulse of germ and birth,
Was shrunken hard and dry,
And every spirit upon the earth
Seemed fervourless as I.
"Germ" refers to the seeds which will replant and regrow in the spring. Given the desolate landscape and low expectations for the future, the speaker supposes that every person and/or creature on earth has no hope in a rebirth or spring.
In the third stanza, the speaker hears the thrush's song. It is an "evensong" which just means an evening song. But the theme of winter, death, and the close of the day/century is carried on as it is evening. Like the century, the thrush is "aged." Like the barren scene, the thrush is frail and gaunt. However, despite all this hopelessness, the thrush flings his soul "upon the growing gloom" and his joy is "illimited" (has no limit).
In the fourth stanza, the speaker is bewildered by this joyous song at such a hopeless time. That is, there was nothing "written on terrestrial things" (nothing happy about the landscape) which could suggest a happy song because everything look desolate and dark. In the last few lines, the speaker supposes that the thrush knows something he doesn't; something to be hopeful for.
One of Hardy's themes in this poem was his dismay with British imperialism and the growth of industrialization. In a more general context, and one which does not depend upon Hardy's authorial intent, the poem is about a hopeless situation. In such a desolate and desperate time, a hopeful sentiment (or song) would seem odd, a stark contrast, or it might even seem inappropriate. But perhaps in such a hopeless moment, this is the best time for a joyful song.