Summary
After everyone goes to sleep, the snow begins. It covers the brown city in white, which falls slowly, unceasingly, and quietly. The snow muffles the familiar urban sound of traffic and disguises the forms of buildings, making everything appear smooth and similar, and disguising anything unusual.
Analysis
These nine lines collectively create a long, winding, and unusual sentence. The sentence's relatively simple declarative content—that snow fell on the city while its people were sleeping—is very nearly obscured by its mass of descriptive language. Snow, the poem explains, makes everything look similar and sound muted. On every level, Robert Bridges recreates and imitates the blanketing, blurring quality of snowfall within the poem. One way in which he does this is clear from just a glance at the page. Rather than splitting the poem into discrete stanzas, Bridges uses one long stanza in which every line has a roughly similar length. The poem, therefore, looks like a cascading, undifferentiated sheet of text. Long sentences contribute to this effect too: while shorter ones might give the sense of a fractured, abrupt aural landscape, long ones add to the impression of ceaselessness. However, long sentences can also create a feeling of speed, which isn't exactly what Bridges is going for—he emphasizes slowness with words like "lazily" and "drifting." In order to slow down the long sentences, he uses end-stopped lines (that is to say, lines with punctuation at the end). The commas, semicolons, and colons concluding the lines of "London Snow" make its pace feel slow and leisurely while preserving its essential seamlessness.
Grammatically, this first long sentence is absolutely packed with gerunds (verbs ending in "ing") and adverbs. For instance, the line "Into angles and crevices softly drifting and sailing" contains an adverb (softly) and two gerunds. Poets actually tend to avoid these grammatical tendencies, precisely because they often create a feeling of imprecision or abstraction. A word like "drifting," for instance, offers less vividness than a verb like "drift," and conveys a feeling of temporal vagueness: the action is undefined and ongoing, creating a perpetual, suspended present. Adverbs, too, are often considered inferior to active and precise verbs when it comes to creating a vivid, dynamic scene. So why does Bridges go out of his way to choose these infamously imprecise forms? Well, probably because abstraction and imprecision are exactly what he wants to get across. He's dealing with an almost paradoxical poetic problem: he wants to portray a scene defined by inactivity, sameness, and inaction, but he doesn't want it to feel boring or monotonous. Gerunds and adverbs create a kind of vivid mutedness, helping him with that difficult task. Meanwhile, the sheer repetitiveness of this first sentence, so dominated by gerunds and adverbs, mimics the repetitiveness of falling snow.