Sentence:  In the mean time I have another trouble to give you, if you will <WSD>oblige</WSD> me in it; and that is to get me a sight of the famous Orrery, which I have heard you and others so often speak of; and which I think was made by Mr. Rowley, the famous Mathematical Instrument-Maker. 
Meaning of the word marked with <WSD> tags:  To do someone a service or favour (hence, originally, creating an obligation).