IN Mandarin, change is handily expressed: a quick le at the end of the sentence will do it, as in tamen gaozing le - now they are happy. Everywhere there are limits, but the thin fattens, the cloudy clears. What's dry dampens. The barren bears.... Ralph invented his grammar on the fly; even Theresa struggled to put her Chinese thoughts into English. But now she had English thoughts too - that was true also. They all did. There were things they did not know how to say in Chinese. The language of outside the house had seeped well inside - Cadillac, Pyrex, subway, Coney Island, Ringling Brothers and Barnum & Bailey Circus. Transistor radio. Theresa and Helen and Ralph slipped from tongue to tongue like turtles taking to land, taking to sea; though o ne remained their more natural element, both had become essential.