Before I analyze the essay, let's take a brief moment to clarify the literary device. Tone, is the attitude cultivated by the author, poet, or artist of a work and it is communicated to the audience through diction, syntax, organization, and style.
Emerson's tone in his essay "Nature" meanders as he explores man's relationship with nature. His first section, in which he discusses the stars and nature as a whole, is reverent. He waxes romantic on the seemingly infinite nature of stars, and uses this to transition to the true beauty and amazement of nature.
However, at the end of this transition, he begins to shift into a more analytical tone, exploring the identity of a person who can truly appreciate nature, even as an adult. Through his discussion, he comes to a conclusion: "few adult persons can see nature." Despite the negativity, outwardly apparent in this statement, Emerson does not despair. Instead, he describes the utter beauty of nature to someone who truly appreciates it. This awed and admiring tone is punctuated by his triumphant declaration of being one within nature: "I become a transparent eye-ball; I am nothing; I see all; the currents of the Universal Being circulate through me; I am part or particle of God."
As Emerson's essay draws to a close, his tone reverts to academic and didactic, in which he explains certain truths about nature to his audience, hoping to win them over to his side, the side of nature's true devotees.