Compass has a half-life of only about 12 years, so a compass that contains 120 mCi of tritium when new will contain only 60 when it is 12 years old, 30 when it is 24 years old, and so on. Consequently, the illumination of the display will fade. Mariners' compasses can have two or more magnets permanently attached to a compass card, which moves freely on a pivot. A "lubber line", which can be a marking on the compass bowl or a small fixed needle, indicates the ship's heading on the compass card. Traditionally the card is divided into thirty-two points
How Many More Years How Many More Years "How Many More Years" is a blues song written and originally recorded by Howlin' Wolf (born Chester Burnett) in July 1951. Recorded at the Memphis Recording Service – which later became the Sun Studio – it was released by Chess Records and reached no.4 on the "Billboard" R&B chart. Musician and record producer T-Bone Burnett has described "How Many More Years" as "in some ways... the first rock’n’roll song...". It was a double-sided hit with "Moanin' at Midnight", which reached no.10 on the R&B chart. After military service, Chester Burnett performed as a blues singer and