mercy = lovingkindness, or grace (as in Psa_36:7).
LORD. Hebrew. Jehovah.App-4. mountains: i.e. great and mighty.
Thy judgments = And Thy just decrees. The "And" was cancelled by the Massorites (see the Babylonian Talmud Nedarim, 37b-38a). Ginsburg Int. (pp. 307-8).
LORD = Jehovah, because of preservation, which is more than creation. See App-4.