"The summer months passed in the most active preparation for getting the large twenty-foot ready against the next winter. The carpenters and smiths of Datchet were in daily requisition, and, as soon as patterns for tools and mirrors were ready, my brother went to town to have them cast, and, during the three or four months ALEXANDER could be absent from Bath, the mirrors and optical parts were nearly completed.
"But that the nights after a day of toil were not given to rest, may be seen by the observations on _Mars_, of which a paper, dated December 1, 1783, was given to the Royal Society. Some trouble, also, was often thrown away, during those nights, in the attempt to teach me to remeasure double stars with the same micrometers with which former measures had been taken, and the small twenty-foot was given me for that purpose. . . . I had also to ascertain their places by a transit instrument lent for that purpose by Mr. DALRYMPLE; but, after many fruitless attempts, it was seen that the instrument was, perhaps, as much in fault as my observations."
"I have now finished my third review of the heavens. The first was made with a Newtonian telescope something less than seven feet focal length, a power of 222, and an aperture of four and a half inches. It extended only to stars of the first, second, third, and fourth magnitudes. My second review was made with an instrument much superior to the other, of 85.2 inches focus, 6.2 inches aperture, and power 227. It extended to all the stars of HARRIS'S maps and the telescopic ones near them, as far as the eighth magnitude. The Catalogue of Double Stars and the discovery of the _Georgium Sidus_, were the results of that review. The third was with the same instrument and aperture, but with a power of 460. This review extended to all the stars of FLAMSTEED'S Catalogue, together with every small star about them, to the amount of a great many thousands of stars. I have, many a night, in the course of eleven or twelve hours of observation, carefully and singly examined not less than 400 celestial objects, besides taking measures, and sometimes viewing a particular star for half an hour together."
The fourth review began with the twenty-foot, in 1784.