It has long been suspected that the famous star 61 Cygni, which is a double star, forms a binary system--that is, that the two stars composing it revolve round their common centre of gravity and move together through space. But measures of parallax made by Herman S. Davis and Wilsing seem to show a difference of parallax between the two components of about 0·08 of a second of arc. This difference of parallax implies a distance of about 2¼ "light years" between the two stars, and "if this is correct, the stars are too remote to form a binary system. The proper motions of 5"·21 and 5"·15 seem to show that they are moving in nearly parallel directions; but are probably slowly separating." Mr. Lewis, however, thinks that a physical connection probably exists.[303] Dante speaks of the four bright stars of the Southern Cross as emblematical of the four cardinal virtues, Justice, Temperance, Fortitude, and Prudence; and he seems to refer to the stars Canopus, Achernar, and Foomalhaut under the symbols of Faith, Hope, and Charity. The so-called "False Cross" is said to be formed by the stars κ, δ, ε, and ι of the constellation Argo Navis. But it seems to me that a better (although larger) cross is formed by the stars α Centauri and α, β, and γ of Triangulum Australis. Mr. Monck has pointed out that the names of the brightest stars seem to be arranged alphabetically in order of colour, beginning with red and ending with blue. Thus we have Aldebaran, Arcturus, Betelgeuse, Capella, Procyon, Regulus, Rigel, Sirius, Spica and Vega. But as the origin of these names is different, this must be merely a curious coincidence.[304] And, to my eye at least, Betelgeuse is redder than Arcturus. The poet Longfellow speaks of the-- "Stars, the thoughts of God in the heavens,"[305] and Drayton says-- "The stars to me an everlasting book In that eternal register, the sky."[306] Observing at a height of 12,540 feet on the Andes, the late Dr. Copeland saw Sirius with the naked eye less than 10 minutes before sunset.[307] He also saw Jupiter 3{m} 47{s} before sunset; and the following bright stars--Canopus, 0{m} 52{s} before sunset; Rigel (β Orionis) 16{m} 32{s} after sunset; and Procyon 11{m} 28{s} after sunset. From a height of 12,050 feet at La Paz, Bolivia, he saw with the naked eye in February, 1883, ten stars in the Pleiades in full moonlight, and seventeen stars in the Hyades. He also saw σ Tauri double.[308]