The face of Mr. Henchard beamed forth a satisfaction that was almost fierce in its strength. "Now you are my friend!" he exclaimed. (9.43)
Henchard both loves and hates with fierceness. He's hardly met Farfrae, yet he proclaims that they're friends with "fierce" satisfaction.
"I am the most distant fellow in the world when I don't care for a man," he said. "But when a man takes my fancy he takes it strong." (9.44)
Henchard realizes this about himself – he loves passionately, strongly, and suddenly. He tends to go with his gut about people. It sometimes guides him well (such as when he trusts Farfrae to manage his business when he hardly knows him) and sometimes guides him badly (such as when he suspects that Farfrae is trying to undermine his authority and flies into a jealous rage).
He was plainly under that strange influence which sometimes prompts men to confide to the new-found friend what they will not tell to the old. (12.9)
Henchard trusts Farfrae completely from the very beginning of their friendship – not only with his business, but with his personal secrets. The narrator describes this as a fairly commonplace, if "strange" impulse. It's something that could happen to many people.
"Now what would you do – I want your advice?"
"I think I'd run the risk, and tell her the truth. She'll forgive ye both."
"Never!" said Henchard. "I am not going to let her know the truth." (12.31-33)
Henchard asks for Farfrae's advice, but when Farfrae doesn't tell him what he wants to hear, he rejects the advice instantly: "Never!"
Her quiet eye discerned that Henchard's tigerish affection for the younger man, his constant liking to have Farfrae near him, now and then resulted in a tendency to domineer, which, however, was checked in a moment when Donald exhibited marks of real offence. (14.27)
Henchard's fierce affection for Farfrae is now described as "tigerish." Sounds like he could become dangerous.
"'Od d--n it," cried Henchard, "what's all the world! I like a fellow to talk to. Now come along and hae some supper, and don't take too much thought about things, or ye'll drive me crazy." (14.27)
If you're confused about the beginning of Henchard's speech here, don't worry – you're not alone. "'Od" is just Henchard's dialect: it's his way of saying "God" when he's going to swear. D--n is the way writers and publishers wrote the word "damn" to avoid censorship. Henchard invites Farfrae to supper because he wants the company – he "like[s] a fellow to talk to." Henchard was lonely for a long time before Farfrae showed up.
She looked from the window, and saw Henchard and Farfrae in the hay-yard talking, with that impetuous cordiality on the mayor's part, and genial modesty on the younger man's, that was now so generally observable in their intercourse. Friendship between man and man; what a rugged strength there was in it, as evinced by these two. And yet the seed that was to lift the foundation of this friendship was at that moment taking root in a chink of its structure. (15.7)
Once again, Henchard and Farfrae's friendship is observed from above by Elizabeth-Jane. She notices that it has a "rugged strength" in it. The narrator warns us that something is about to come between them.
Henchard's manner towards Farfrae insensibly became more reserved. He was courteous – too courteous – and Farfrae was quite surprised at the good breeding which now for the first time showed itself among the qualities of a man he had hitherto thought undisciplined, if warm and sincere. (16.1)
Henchard begins to feel jealous of Farfrae's popularity and superior intelligence. He starts acting overly polite to him. Farfrae, though, is so far from being suspicious that he just thinks that Henchard is showing "good breeding" by being polite and courteous.
Henchard was a little moved. "I – sometimes think I've wronged ye!" he said, in tones which showed the disquietude that the night shades hid in his face. He shook Farfrae abruptly by the hand, and hastened away as if unwilling to betray himself further. (32.38)
Even after their friendship has collapsed, Farfrae is capable of acting with generosity toward Henchard. After all, he never did anything to deserve Henchard's hatred, and he never understands where it came from. So when he offers to give Henchard any of his household furniture that he still wants, Henchard is touched by his generosity.
Henchard looked down upon him in silence, and their eyes met. "O, Farfrae – that's not true!" he said, bitterly. "God is my witness that no man ever loved another as I did thee at one time. [. . .] And now – though I came here to kill 'ee, I cannot hurt thee! Go and give me in charge – do what you will – I care nothing what comes of me!" (38.34)
Henchard has beaten Farfrae in a fight, even with one hand tied behind his back. Farfrae tells him to go ahead and kill him, since he's wanted to for so long. But Henchard can't bring himself to do it. Even though they're no longer friends, he can't forget how close they used to be.