What do conclusion does the cartoon support about the historical context of great britain at the time it was made

The iconic cartoon that you are talking about is probably a man standing on top of a country with his legs spread wide. 

This cartoon suggests that Europeans are powerful enough to subdue an entire continent. This was a satirical image that was drawn during the time of the colonization of the British Empire in Africa.
This image was inspired by the plans of the British empire to create Telegraph lines all over Africa promoting the further spread of its colonies through faster communication. The picture depicts the colonial mentality of the British empire in general as well as the struggle of Africans to claim their own land.

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