Three more slyly suggestive episodes--the most distinctive yet--in the life of boyish terrier Alex and the inscrutable cat. In ""Alex's Bone,"" he keeps misconstruing the cat's meaning--as who wouldn't? ""'Did you ever bury a bone and then forget where?' he asked the cat. 'Never,' said the cat. 'That's amazing,' said Alex."" But the cat, it transpires, can be mistaken too. (Alex isn't digging to dig up the bone, he just wants to find out where it is.) ""Alex's Phase"" is about chewing--mittens, magazines, ""everything."" Out of that phase, he gets into cat-chasing, very briefly. Another mitten? ""Oh, well, what good is one mitten?"" ""Alex and the Cold Air"" is sheer exuberance: Alex in his winter element--after a brief try at hibernation, brief talk of migrating--and the cat hunching down. Laconic, offside--but based on familiar verities and much amplified by Carrick's naturalistic, almost painterly illustrations which impart dignity and character, lightly tinged with humor, to Alex and the cat.