Charles Darwin letters reveal his emotional side

In a collection of previously unpublished letters soon to be made available online, naturalist Charles Darwin reveals a highly emotional and personal side.

In letters to his closest friend, the botanist Joseph Hooker, he pours out his grief over the death of his daughter-in-law, Amy. He also speaks of his ideas on evolution for the first time - something he writes was like "confessing to a murder".

Of the many letters that Darwin wrote and received in his life, among the most important were his correspondence with his friend of 40 years, Joseph Hooker. As well as tracking the development of Darwin's scientific ideas, the letters give an intimate insight into a Victorian friendship.

Almost the entire collection - more than 1,400 letters - will soon be published by Cambridge University's Darwin Correspondence Project.

Darwin also used Hooker as a sounding board for his scientific ideas. Because of his position at Kew, Hooker was able to put him in touch with a wide network of scientific contacts. This was vital for Darwin, says Mr White: "It was particularly important because he had chosen to live rather a reclusive life. He didn't have an institutional position, so Darwin relied upon letters more than most people at the time for his window on the world."It is this openness - as well as the light they shed on Darwin's work - that give the letters their fascination.