THE OPERA.--Immediately upon the departure of JENNY LIND, Mr. Maretzek opened the doors of the Astor Place Opera House for a short season, preparatory to his summer campaign in Castle Garden. Under his auspices BOSIO has reappeared, and BETTINI has made his bow. BOSIO is so beautiful a woman, she has a voice so subtly sweet and sympathetic, a style of singing so simple and sufficient, and an instinctive feminineness of feeling fine enough to make her acting always agreeable, that her impression as a Prima Donna is the most symmetrical we have known in New-York. Her womanliness is her charm and her success. Even in characters of so grandiose proportions in the imagination, as _Lucrezia_, she never drops for a moment the interest of the spectator, although it is new to him to find a tender feeling in his regard for the Borgia. This tenderness, however, is not fatal to the artistic effect. It is that quality of feeling which he would have for a lost but lovely Magdalen. BOSIO'S _Zerlina_ is another quite perfect representation. Its arch grace and sparkling beauty have never been surpassed by any Zerlina we have seen. BOSIO, however, sketches rather than colors. Her acting is a suggestive outline which the imagination naturally fills--and, within the range of singers possible to us, we could select none so singularly fascinating as Bosio for the summer moonlight at Castle Garden. BETTINI is a young man, with a fresh, sweet, sympathetic tenor voice, which happily harmonizes with BOSIO'S. He has rather too magniloquent a style both of acting and singing, but is a very agreeable artist. We could lay in the shadows of his portrait delicately, yet deeply enough, by saying that he is _young_. He has made a decided hit upon the town, and the first evening at Castle Garden attracted an audience of not less than three thousand. Donizetti's opera of _Marino Faliero_ has been produced at Castle Garden, for the first time in America. It is only second rate music, but was admirably sung by the company. MARINI looks the Doge and wears the ducal robe with great dignity and success. NICHOLAS VON DER FLUE. WRITTEN FOR THE INTERNATIONAL MONTHLY MAGAZINE BY THE AUTHOR OF "RURAL HOURS." The fifteenth century proved an eventful and important period of Swiss history. The age which preceded it gave birth to the people, and brought them an independent existence and a name; but it left them at its close the mere skeleton of a political body, and it was not until a later day that their national constitution received fulness and development--it was not until the fifteenth century that the people acquired a clearly distinct character and position among the countries of Europe.