That the brother and sister were still the first to each other is shown by their correspondence, the manner in which they always consulted each other, and kept each other informed of the incidents in each other's lives. On the morning of his marriage Frederick writes to inform his sister of the event:-- "_Salzdalum, Noon, 12th June, 1733._ "MY DEAR SISTER,--A minute since the whole ceremony was got finished, and, God be praised, it is over! I hope you will take it as a mark of my friendship that I give you the first news of it. I hope I shall have the honour to see you again soon, and to assure you, my dear sister, that I am wholly yours. I write in great haste, and do nothing that is merely formal. Adieu. "FREDERICK." For some years succeeding this period Wilhelmina and her brother do not seem, apart from their correspondence, to have had much personal intercourse. An important and interesting factor in their lives was their acquaintance and correspondence with Voltaire. This appears to date from the year 1736. Doubtless, during their youthful studies, pursued together years before, in spite of prohibition and difficulty, they had become acquainted with the writings of this great author. Now Frederick opened a correspondence, which, after continuing for four years, ripened into a closer acquaintance. They, however, never met until Frederick became King of Prussia. This event took place upon the death of his father, in May, 1740. In the month of November following Wilhelmina paid a memorable visit of several months to her brother, the King, at Rheinsburg, his stately and charming residence near Berlin, when he introduced Voltaire to her with the words, "I here present you to my loved sister." In connection with this visit we have the following pleasing picture:--"When evening comes, with the rough and chilly autumn air so common to that part of Germany, the candles are lit in the Queen's apartments, beautifully decorated by Pesne. The King, who has all day sat brooding over serious undertakings against the House of Hapsburg, now makes his appearance. The concert begins. The King leads the Margravine to the piano, and then takes his flute. During the pauses between the different pieces the Margravine holds philosophic and other discussions with Maupertis, Algarotti, Jordan, and Keyserling; but chiefly with Voltaire, whose society was so new, interesting, and invigorating."[2] The friendship thus formed, though Wilhelmina and Voltaire did not often meet, was continued by an interesting correspondence until the close of her troubled life. [2] "The Margravine of Baireuth and Voltaire." By Dr. George Horn. Translated by H.R.H. Princess Christian. p. 171.