A = 432 Hz, and an 1855 fork gives A = 449 Hz. At La Scala in Milan, the A above middle C rose as high as . 19th- and 20th-century standards The strongest opponents of the upward tendency in pitch were singers, who complained that it was putting a strain on their voices. Largely due to their protests, the French government passed a law on February 16, 1859, which set the A above middle C at 435 Hz. This was the first attempt to standardize pitch on such a scale, and was known as the diapason normal. It became quite a popular pitch standard outside France as well, and has also been known at various times as French pitch, continental pitch or international pitch (the last of these not to be confused with the 1939 "international standard pitch" described below). An 1885 conference in Vienna established this value among Italy, Austria, Hungary, Russia, Prussia, Saxony, Sweden and Württemberg. This was included as "Convention of 16 and 19 November 1885 regarding the establishment of a concert pitch" in the Treaty of Versailles in 1919 which formally ended World War I. The diapason normal resulted in middle C being tuned at about . An alternative pitch standard known as philosophical or scientific pitch fixes middle C at (that is, 28 Hz), which results the A above it being approximately in equal temperament tuning. The appeal of this system is its mathematical idealism (the frequencies of all the Cs being powers of two). This system never received the same official recognition as the French A = 435 Hz and has not been widely used. This tuning has been promoted unsuccessfully by the LaRouche movement's Schiller Institute under the name Verdi tuning since Italian composer Giuseppe Verdi had proposed a slight lowering of the French tuning system. However, the Schiller Institute's recommended tuning for A of 432 Hz is for the Pythagorean ratio of 27:16, rather than the logarithmic ratio of equal temperament tuning. British attempts at standardisation in the 19th century gave rise to the old philharmonic pitch standard of about A = 452 Hz (different sources quote slightly different values), replaced in 1896 by the considerably "deflated" new philharmonic pitch at A = 439 Hz. The high pitch was maintained by Sir Michael Costa for the Crystal Palace Handel Festivals, causing the withdrawal of the principal tenor Sims Reeves in 1877,