Why did axel not want to go on the trip?

is a novel by ,
originally published in French in the year 1864. The story is narrated by Axel Lidenbrock, a
young man who lives in Hamburg, Germany with his uncle Otto Lidenbrock, a professor of
mineralogy.

Axel assists Otto with his experiments, and definitely takes
after his uncle in terms of having a scientific mind. As he says himself:

I will admit that I devoured geological science with great relish; I
had mineralogists blood in my veins, and never felt bored in the company of my precious
pebbles.

When Otto finds a manuscript written in
Icelandic runes in a shop, he takes it home, and a separate piece of parchment with a message
jumbled in a runic code falls out. Axel, almost by accident, figures out how to decode its
secret message before Otto does. Axel reads it and finds that the message describes a way to
travel in order to reach the center of the earth. Knowing immediately that his Uncle will want
to take this journey, he says the following:

€˜No! Im not
going to tell my uncle. It would be terrible if he got to know about such a journey. Hed just
want to have a go himself. Nothing would stop a geologist of such determination. He would leave
anyway, against all obstacles, whatever the cost. And hed take me with him, and we wouldnt come
back. Never. Not nohow!

Later on, after Axel eventually
gives in and tells his uncle how to read the code, and Otto declares that they're going to go on
this journey, Axel tries to reason with him, saying:

All
right, I accept that this Saknussemm wrote the message, but does it necessarily follow that he
actually carried out the journey? Couldnt the old parchment just be a practical joke?

And so, we see that Axel does not want to try to go to the center
of the earth because he doesn't fully believe that the feat is possible, and thinks that they
would die trying.

(Note that any quotes I used in this answer may be slightly
different from the ones in your own copy of the book, as there are multiple different English
translations of Journey to the Center of the Earth.)