as the shift of an inch in the position of a telescope.  It was her telescope in fact that had gained in range—­just as her danger lay in her exposing herself to the observation by the more charmed, and therefore the more reckless, use of this optical resource.  Not under any provocation to produce it in public was her unremitted rule; but the difficulties of duplicity had not shrunk, while the need of it had doubled.  Humbugging, which she had so practised with her father, had been a comparatively simple matter on the basis of mere doubt; but the ground to be covered was now greatly larger, and she felt not unlike some young woman of the theatre who, engaged for a minor part in the play and having mastered her cues with anxious effort, should find herself suddenly promoted to leading lady and expected to appear in every act of the five.  She had made much to her husband, that last night, of her “knowing”; but it was exactly this quantity she now knew that, from the moment she could only dissimulate it, added to her responsibility and made of the latter all a mere question of having something precious and precarious in charge.  There was no one to help her with it—­not even Fanny Assingham now; this good friend’s presence having become, inevitably, with that climax of their last interview in Portland Place, a severely simplified function.  She had her use, oh yes, a thousand times; but it could only consist henceforth in her quite conspicuously touching at no point whatever—­assuredly, at least with Maggie—­the matter they had discussed.  She was there, inordinately, as a value, but as a value only for the clear negation of everything.  She was their general sign, precisely, of unimpaired beatitude—­and she was to live up to that somewhat arduous character, poor thing, as she might.  She might privately lapse from it, if she must, with Amerigo or with Charlotte—­only not, of course, ever, so much as for the wink of an eye, with the master of the house.  Such lapses would be her own affair, which Maggie at present could take no thought of.  She treated her young friend meanwhile, it was to be said, to no betrayal of such wavering; so that from the moment of her alighting at the door with the Colonel everything went on between them at concert pitch.  What had she done, that last evening in Maggie’s room, but bring the husband and wife more together than, as would seem, they had ever been?  Therefore what indiscretion should she not show by attempting to go behind the grand appearance of her success?—­which would be to court a doubt of her beneficent work.  She knew accordingly nothing but harmony and diffused, restlessly, nothing but peace—­an extravagant, expressive, aggressive peace, not incongruous, after all, with the solid calm of the place; a kind of helmetted, trident-shaking pax Britannica.