Sentence:  He concludes with an account of several experiments he had lately made in the art of gunnery; upon which, in return to Flamstead's remark of his errors in the eclipse, he takes notice of a mistake made by that Astronomer, in a table of horizontal ranges, wherein a <WSD>mounture</WSD> of 42 degrees was put for the utmost random, which he conceived to be demonstrably 45 degrees. 
Meaning of the word marked with <WSD> tags:  The angle of ascension.