Former posting: I also felt curious about a stereotyped repetition (stemming from VN!) when he mentions motor engines.  The word "powerful" appears twelve times in PF. In six of them he is describing his car (there's another one, related to the King's powerful motorboat). He seems to be excessively aware of the relation between engine power and speed of locomotion, as we also find it in his note about the forces that propelled the verbal advance of Gradus (the assassin employs cars, trains, escalators and airplanes but he is felt as if he were maintaining a "sustained glide over sea and land" thanks to the sensuous form endowed to him by inexorable fate - through CK's or J.Shade's moving pencils) [...] CK's note to lines 131-32: "Although Gradus availed himself of all varieties of locomotion — rented cars, local trains, escalators, airplanes — somehow the eye of the mind sees him, and the muscles of the mind feel him, as always streaking across the sky with black traveling bag in one hand and loosely folded umbrella in the other, in a sustained glide high over sea and land. The force propelling him is the magic action of Shade’s poem itself, the very mechanism and sweep of verse, the powerful iambic motor. Never before has the inexorable advance of fate received such a sensuous form (for other images of that transcendental tramp’s approach see note to line 17). What about electricity? That's how the "muscles of the mind" work, no?

Jansy Mello: An adjective applied to Gradus in CK's note to lines 131-132 (see above), "transcendental tramp", caught my interest. In line 17, where his approach is described, we read:
"We shall accompany Gradus in constant thought, as he makes his way from distant dim Zembla to green Appalachia, through the entire length of the poem, following the road of its rhythm, riding past in a rhyme, skidding around the corner of a run-on, breathing with the caesura, swinging down to the foot of the page from line to line as from branch to branch, hiding between two words (see note to line 596), reappearing on the horizon of a new canto, steadily marching nearer in iambic motion, crossing streets, moving up with his valise on the escalator of the pentameter, stepping off, boarding a new train of thought, entering the hall of a hotel, putting out the bedlight, while Shade blots out a word, and falling asleep as the poet lays down his pen for the night."

How could I have missed it before? Gradus is part of the thoughts,words, rythm and structure of "Pale Fire." This, of course, is no novelty as a construct but, for me, the emotional experience suffered a turn with the addition of "transcendent," most probably associated to the "inexorable advance of death."  Kinbote's commentary also reveal the project of representing, and controlling death by the means of literary devices.

At the end of Kinbote's commentary, indicating line 1000 (returning to the first line of the poem), this transcendental Gradus will reappear:  

" 'And you, what will you be doing with yourself, poor King, poor Kinbote?' a gentle young voice may inquire.

God will help me, I trust, to rid myself of any desire to follow the example of two other characters in this work. I shall continue to exist. I may assume other disguises, other forms, but I shall try to exist. I may turn up yet, on another campus [...] I may pander to the simple tastes of theatrical critics and cook up a stage play, an old-fashioned melodrama with three principles: a lunatic who intends to kill an imaginary king, another lunatic who imagines himself to be that king, and a distinguished old poet who stumbles by chance into the line of fire, and perishes in the clash between the two figments. Oh, I may do many things![...]. But whatever happens, wherever the scene is laid, somebody, somewhere, will quietly set out — somebody has already set out, somebody still rather far away is buying a ticket, is boarding a bus, a ship, a plane, has landed, is walking toward a million photographers, and presently he will ring at my door — a bigger, more respectable, more competent Gradus."

It seems to me that the Author, along with his characters, recognizes that - inspite of all his efforts and despite of the transcendent power of literature and the fictional world - he is doomed to disappear because death is also a part of the process of creation.