The River Thames at London Bridge, choked by ice floes some 2 metres thick, in early February, 1895. The severe winter of 1894 -1895 ended on March 1st. Many climatologists have come to view this winter as the end of the Little Ice Age and the culmination of a decade of harsh winters in Britain. This winter also affected most of Europe and North America very severely, causing mass unemployment. Shipping on the River Thames was greatly disrupted and most workers were without sustenance. The Little Ice Age is defined as the climate interval that existed between the 14th century and the mid 19th century. Thereafter there was a change in climate and subsequently the Thames has not frozen over. Among the scientists in the 19th century who proposed various theories on the causes of climate changes were Joseph Fourier (in 1824) and John Tyndall (in 1859).