The love of Catherine and Heathcliff

"... It would degrade me to marry Heathcliff, now; so he shall never know how I love him; and that, not because he's handsome, Nelly, but because he's more myself than I am. Whatever our souls are made of, his and mine are the same, and Linton's is as different as a moonbeam from lightning, or frost from fire. [...] What were the use of my creation if I were entirely contained here? My great miseries in this world have been Heathcliff's miseries, and I watched and felt each from the beginning; my great thought in living is himself. If all else perished, and he remained, I should still continue to be; and, if all else remained, and he were annihilated, the universe would turn to a mighty stranger. I should not seem a part of it. My love for Linton is like the foliage in the woods. Time will change it, I'm well aware, as winter changes the trees- my love for Heathcliff resembles the eternal rocks beneath- a source of little visible delight, but necessary. Nelly, I am Heathcliff- he's always, always in my mind- not as a pleasure, any more than I am always a pleasure to myself- but, as my own being- so don't talk of our separation again- it is impracticable..." 
(Catherine) 

"... I wish you had sincerity enough to tell me whether Catherine would suffer greatly from his loss. The fear that she would restrains me; and there you see the distinction between our feelings- Had he been in my place, and I in his, though I hated him with a hatred that turned my life to gall, I never would have raised a hand against him. You may look incredulous, if you please! I never would have banished him from her society, as long as she desired his. The moment her regard ceased, I would have torn his heart out, and drank his blood! But, till then- if you don't believe me, you don't know me- till then, I would have died by inches before I touched a single hair on his head! [...] You suppose she has nearly forgotten me? Oh Nelly! You know she has not! You know as well as I do, that for every thought she spends on Linton, she spends a thousand on me! At a most miserable period of my life, I had a notion of the kind, it haunted me on my return to the neighbourhood, last summer, but only her own assurance could make me admit the horrible idea again. And then, Linton would be nothing, nor Hindley, nor all the dreams ever I dreamt. 2 words would comprehend my future- death and hell- existence, after losing her, would be hell. Yet I was a fool to fancy for a moment that she valued Edgar Linton's attachment more than mine- If he loved with all the powers of his puny being, he couldn't love as much in 80 years, as I could in a day. And Catherine has a heart as deep as I have; the sea could be as readily contained in that horse-trough, as her whole affection be monopolised by him- Tush! He is scarcely dearer to her than her dog, or her horse- It is not in him to be loved like me, how can she love in him what he has not?..." 
(Heathcliff)

("Wuthering Heights" by Emily Bronte)