In the seventeenth century, India would have seemed impossibly distant from England. A few decades before Andrew Marvell entered Parliament, one of its leading lights had been Sir Thomas Roe, who was sent as a diplomat to the court of the Emperor Jahangir by King James I. Roe returned with extraordinary descriptions of life in India. For someone used to the small Humber River in Northern England, an account of the mighty Ganges with its ghats must have seemed like something from another world. Marvell uses the physical distance between the two rivers, as well as the differences between the two countries they represent, to emphasize how far apart the speaker and the eponymous mistress could afford to be in the slow, unhurried love affair he describes at the beginning of the poem.
The image that contrasts with this one in the third part of the poem, therefore, is the image depicting the greatest physical proximity:
Let us roll all our strength and all
Our sweetness up into one ball,
Rather than being thousands of miles apart, by different rivers in different continents, the speaker wants the two of them to be rolled in a ball together, the essential attributes of each mixed together so that they are united as one. This is an image of amorous union but also of spiritual and emotional connectedness.