In chapter twenty-four of Mary Shelley's novel Frankenstein, Victor gives two speeches. The first speech is given to Walton and the second is given to Walton's men.
In the speech to Walton, Victor thanks Walton for his friendship (important given this is one thing Walton openly desired as noted in Letter III). Victor's speech details the difference between childhood friends and friends made later in life. Essentially, Victor believes that childhood friends are those which can be fooled and friends made later in life may possess suspicions. The final lines of Victor's speech refer to the two things on earth which he must do: kill his creature and die.
The tone of this speech mirrors Victor's sadness (given his loss of all he loved). Now, looking back, Victor realizes the catastrophic mistakes he made.
In his second speech to Walton's crew, Victor denounces them for questioning the desire of Walton. Victor recognizes Walton's greatness and desire (the crew does not). Given that Walton and Victor share a desire (a quest for knowledge), Victor finds it necessary to defend Walton's decisions to his crew. Victor, in the closing of the speech, tells Walton's crew to have the strength which Walton does.
The tone of this speech is one of disappointment and reproachfulness. Victor understands what it means to be questioned and not believed in. His knowledge with what this evokes in a person leads him to scrutinize Walton's crew.