THE art of letter writing, we are constantly being told, is dying fast. Telegrams, telephones and modern transport have killed it. Certainly the social history of this age, when it comes to be written, will not be illumined by those graceful letters whose very turn of phrase is witty, with which our ancestors crossed and crossed again their paper before it was sanded, folded and sealed, and entrusted to the courier who would carry it down miry roads and across desolate heaths to convey the news of the town to some lonely country house. But even today letter writing is still indulged in to a limited extent, and after all, by the time they write the social history of our age, they will probably admire even our limited capacity, for in those days even the conventional ' Writing' at the end of the telegram will have passed away.