Although both rebellions were put down in short order, the British government sent Lord Durham to investigate the causes. He recommended self-government be granted and Lower and Upper Canada be re-joined in an attempt to assimilate the French Canadians. Accordingly, the two colonies were merged into the Province of Canada by the "Act of Union 1840", with the capital at Kingston, and Upper Canada becoming known as Canada West. Parliamentary self-government was granted in 1848. There were heavy waves of immigration in the 1840s, and the population of Canada West more than doubled by 1851 over the previous decade. As a result, for the first time, the English-speaking population of Canada West surpassed the French-speaking population of Canada East, tilting the representative balance of power.