in extremity: excessively

modern: ordinary

sad: serious

emulation: envy

fantastical: imaginative

politick: cunning crafty

nice: wanton, capricious

sundrie contemplations of my travells: sundrie = sundry, meaning several different things; the variety of things I have seen and thought when traveling

most humorous sadnesse: and frequently musing over these envelops me in a very strange seriousness

Yes: yes, but