Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. In one treatise, for example, chapter after chapter is devoted to Deep and Musical Tones, while another author extols the address of Abraham Lincoln, on the occasion of the dedica tion of the Soldiers’ Cemetery at Gettysburg, but fails to give the speech itself or point out in what its excellence consists.