I was reading "The Man who was Thursday" from G. K. Chesterton when I found this sentence which I have not been able to fully understand because of the use of the word 'inroads'. I don't really understand how does the word 'inroads' work, neither in this sentence, nor in general.

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> "If in a few moments this table begins to turn round a little, don't put it down to your inroads into the champagne. I don't wish you to do yourself an injustice." 
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Thank you in advance for your help.