Are historians of 19th century important ? if yes do cute the names & their works .

read utilitarianism , especially Jeremy Bentham and J. S. Mill

you can also read a bit on Auguste Comte and postivist history

should be study writers of science like Robert Darwin & Henry Huxley ?

No. you will not be asked questions on historians . but you may be asked a question on E p Thompson , a historian whose book The history of the English working class is considere...