In general, modern scientific deep-sea exploration can be said to have begun when French scientist Pierre Simon de Laplace investigated the average depth of the Atlantic ocean by observing tidal motions registered on Brazilian and African coasts. He calculated the depth to be , a value later proven quite accurate by echo-sounding measurement techniques. Later on, due to increasing demand for the installment of submarine cables, accurate measurements of the sea floor depth were required and the first investigations of the sea bottom were undertaken. The first deep-sea life forms were discovered in 1864 when Norwegian researchers obtained a sample of a stalked crinoid at a depth of .