“…I have communicated to him without disguise.” (pg. 13)
Here, Walton speaks of his conversations with Victor Frankenstein, who has recently come aboard the ship. The somewhat cumbersome language Shelley occasionally needs explanation, like here. What Walton is saying is that he was able to tell Frankenstein exactly what he meant without having to hide any of his ideas or thoughts like he might have to do with his crew or another friend. Shelley is trying to show that Walton already trusts and feels a deep bond with Frankenstein even though they have just met.