The emperor and empress arrived here on Monday last, and went immediately to Windsor. All London is mad with excitement and enthusiasm, and wherever they move throngs of people follow them. Yesterday they came to Buckingham Palace, and went into the city to be present at a magnificent entertainment at Guildhall. There never was such a crowd seen. In the afternoon at five they received the diplomatic corps at the French Embassy, and I had a long talk with her Majesty, who was most gracious and affable. She is very striking, elegant and graceful. She wore a green silk, flounced to the waist with seven or eight white lace flounces, white lace mantle, and white crape bonnet and feathers. We go to the palace to-night to an evening party, and there I shall even have a better opportunity of seeing them. I was disappointed in the emperor’s appearance—he is very short. Last night they accompanied the queen, in state, to the opera, and there was a grand illumination all over the city. I drove out to see it, but there was such a crush of carriages, men, women and children, that I was glad to get home. They were asking from fifty to one hundred guineas for boxes at the opera, and from ten to forty for single stalls. To-morrow the imperial guests depart, and London will again return to its sober senses. There does not seem to be much gaiety in prospect, but really this visit seems to be the only thing thought of. The Masons are not coming to pay me a visit. Betty has gone to Nice with her father, for his health. It is said the queen will go to Paris at the opening of the exposition in May. Ellen Ward’s marriage is postponed until the fifth of June, by her father’s request. Mr. T. writes he has taken a state-room on the Baltic, which was to sail on the 18th. He has talked of this visit so long that I would not be surprised to hear it ended in nothing. Lu has every thing planned and fixed and _destined_ to take place just as she _wishes_, even that I am to be married in my travelling dress and very quietly. I was at the Crystal Palace on Tuesday, which is truly the most fairy-like and exquisitely beautiful thing that could be made. The royal party go there to-day. The building far exceeds in magnificence the one erecting now in Paris. Mr. —— has lost his favorite sister, and is in great distress, so I have not seen him for a time. I have made another conquest, who comes in the true American style, _every day_. He is rich and keeps a yacht, which costs him £2000 a year. Beaux are pleasant, but dreadfully troublesome...... MAY 3d, 1855. I have yours, dear sister, of March 16th, and really your account of the failures and rascals among your Californians is quite frightful......