Explanation:

 In the 1860s, cotton was a key import, supplying Britain’s busy textile mills. The majority of raw cotton supplies came from America.
However, during the American Civil War (1861–65) raw cotton was no longer being grown and shipped. The British needed to find new sources for their mills, so turned to India to supply their needs.
In 1860, India was supplying 31% of British cotton imports, but the outbreak of war in America saw that supply escalate to 90% in 1862.
Although it declined somewhat, India’s cotton growers were still supplying 67% of Britain’s cotton imports in the later years of the war.