Messrs. WALKER, TILDEN, A.W. WHITE & CO., HOOPER, ELDRIDGE, & CO., AND OTHERS. _Gentlemen_,--Your esteemed favor is before us; and, gratefully accepting your high compliment to our humble endeavors, we respectfully name Thursday, Aug. 17, as the time of the proposed benefit at the Salt-Lake Theatre. Respectfully, HYERS SISTERS. While in St. Joseph, Mo., they elicited from "The Daily Herald" of that city the following encomium:-- "Whoever of our readers failed to visit the Academy of Music last evening missed a rare musical treat. The concert of the Hyers sisters was absolutely the best, furnished those in attendance with the choicest music, which has been in St. Joseph since we have resided here. "The Hyers sisters are two colored ladies, or girls, aged respectively sixteen and seventeen years; but their singing is as mature and perfect as any we have ever listened to. We had read the most favorable reports of these sisters in the California papers, but confess that we were not prepared for such an exhibition of vocal powers as they gave us last night. "Miss Anna Hyers, the eldest, is a musical phenomenon. When we tell musicians that she sings E flat above the staff as loud and clear as an organ, they will understand us when we say she is a prodigy. Jenny Lind was the recipient of world-wide fame and the most lavishly-bestowed encomiums from the most musical critics in the Old and New World simply because she sang that note in Vienna twenty years ago. Parepa Rosa, it is claimed, reached that vocal altitude last summer. But the sopranos who did it flit across this planet like angels. Several competent musicians listened to Anna Hyers last evening, and unanimously pronounced her perfectly wonderful. With the greatest ease in the world, as naturally and gracefully as she breathes, she runs the scale from the low notes in the middle register to the highest notes ever reached by mortal singers. Her trills are as sweet and bird-like as those with which the 'Swedish Nightingale' once entranced the world. In Verdi's famous 'Traviata' there was not a note or modulation wrong: her rendition was faultless, her voice the most sweet and musical we ever listened to. "In the duet, 'There's a sigh in the heart,' her voice was exhibited in wonderful range; and, in the tower-scene from 'Il Trovatore,' its great power was singularly and very agreeably apparent. "We do not remember to have been more completely and agreeably surprised than we were last evening in the matchless excellence of the singing of the Hyers sisters. They deserve a crowded house; and we predict that in Boston or New York, by the most severe critics, they will be pronounced musical prodigies."