What's the difference between thereat and whereinto?

Thereat

Definition:

• (adv.) At that place; there.
• (adv.) At that occurrence or event; on that account.

Example Sentences:

• (1) Factors and methods being complementary and such having an effect of contrary sence are thereat especially described.

Whereinto

Definition:

• (adv.) Into which; -- used relatively.
• (adv.) Into what; -- used interrogatively.

Example Sentences: