You want to know, then, what chalk is?
I suppose you mean what chalk is made of?
Yes.

That is it.
That we can only help by calling in the help of a very great giant whose name is Analysis.
A giant?
Yes.

And before we call for him I will tell you a very curious story about him and his younger brother, which is every word of it true.
Once upon a time, certainly as long ago as the first man, or perhaps the first rational being of any kind, was created, Madam How had two grandsons.

The elder is called Analysis, and the younger Synthesis.

As for who their father and mother were, there have been so many disputes on that question that I think children may leave it alone for the present.
For my part, I believe that they are both, like St.Patrick, "gentlemen, and come of decent people;" and I have a great respect and affection for them both, as long as each keeps in his own place and minds his own business.
Now you must understand that, as soon as these two baby giants were born, Lady Why, who sets everything to do that work for which it is exactly fitted, set both of them their work.