Images Dated 20th February 2006

Abraham Lincoln and his son Tad, 9 February 1864

Abraham Lincoln and his son Tad, 9 February 1864. Lincoln (1809-1865) was the sixteenth President of the United States of America (1861-1865). On Good Friday, 14 April 1865, while at Ford's Theatre, Washington, he was shot by John Wilkes Booth and died the following morning. His son Thomas, also known as Tad (1853-1871), died at the age of 18, probably of tuberculosis

© Art Media / Heritage-Images

Behaviour of a magnetic compass, 1643

Behaviour of a magnetic compass, 1643. If a compass in a box is carried round a globe-shaped magnet (N, centre of picture) with magnetic poles where lines cross (left and right of N), magnets ab at C and D can be set in any position as they are directly between the poles. From Magnes: sive de arte Magnetica by Athanasius Kircher. (Cologne, 1643)

© Ann Ronan Picture Library / Heritage-Images

St Elmos fire

St Elmo's fire. Historical artwork of St Elmo's fire glowing from the tops of a ship's masts. St Elmo's fire is a continuous electrical discharge that occurs towards the end of thunderstorms. The air between the surface and the clouds becomes strongly electrically charged. The electrical fields are most intense at the tips of pointed objects, such as a ship's masts. These very strong electrical fields ionise, or excite, the air molecules, changing them to a plasma state and causing them to release energy as light, resulting in a glow. The ship in this illustration is Christopher Columbus's caravel

© SHEILA TERRY/SCIENCE PHOTO LIBRARY