written in the daytime, or when cloudy nights interfered. Besides this, the twelve-inch speculum was perfected before the spring, and many hours were spent at the turning bench, as not a night clear enough for observing ever passed but that some improvements were planned for perfecting the mounting and motions of the various instruments then in use, or some trials were made of new constructed eye-pieces, which were mostly executed by my brother’s own hands. Wishing to save his time, he began to have some work of that kind done by a watchmaker who had retired from business and lived on Datchet Common, but the work was so bad, and the charges so unreasonable, that he could not be employed. It was not till some time afterwards in his frequent visits to the meetings of the Royal Society (made in moonlight nights), that he had an opportunity of looking about for mathematical workmen, opticians, and founders. But the work seldom answered expectation, and it was kept to be executed with improvements by Alexander during the few months he spent with us. 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 re-measure 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. _July 8._—I began to use the new Newtonian small sweeper, (for a description of this instrument see note to Neb. No. 1, V. class, at the end of the catalogue of first 1000 Neb. and Cl.), but it could hardly be expected that I should meet with any comets in the part of the heavens where I swept, for I generally chose my situation by the side of my brother’s instrument, that I might be ready to run to the clock or write down memorandums. In the beginning of December I became entirely attached to the writing-desk, and had seldom an opportunity after that time of using my newly-acquired instrument.