A Rebbe passes: Not what the eyes of flesh see

On the last time, during his life in this world, that the Rebbe [Rayatz] celebrated his Festival of Liberation [from Russian prison on 12-13 Tammuz], the Rebbe felt it necessary to make the point that matters of holiness are eternal. Moreover (so that no one should misunderstand) he went on to speak specifically of long life, true life that is uninterrupted -- so that we should not think according to what is seen, G-d forbid, by fleshly eyes (for such a situation does not at all apply in the realm of holiness); rather, that we should know that even after the histalkus [passing] there is life without interruption, eternal life, in the case of the Leader of the generation, and through him eternal life is drawn forth for the entire generation....

There is "an extension of Moshe in each and every generation," up to and including the Moshe in our generation, namely, my revered father-in-law, the Rebbe [Rayatz]: Now, too, as before, he is present and diffuses light (like the sun, which at night, too, is present and radiates light).

If we were proceeding together with him we would see that he is now radiating light with all the intensity as previously (and, indeed, in an even higher way). However, since he has ascended, elevation beyond elevation, whereas we did not accompany him but have remained where we were, he is not visible to our fleshly eyes (just as we do not see the sun at night). Nevertheless, in this situation, too, his light extends to all the Children of Israel...

We, admittedly, do not perceive the diffusion of his light. However, as in the above-quoted maxim of the Rebbe Rashab, "If the horse is a horse and the wagon-driver is a wagon-driver, does that mean that the angels aren't angels?!" 

From a talk of the Rebbe following the histalkus (passing) of the Previous Rebbe (Rebbe Rayatz) in 5710 (1950)

http://www.sichosinenglish.org/books/proceeding-together-2/05.htm#t116