From his sister's diary we gather a few particulars illustrative of his mode of life.
On the 4th of October 1806 she writes:—
"My brother came from Brighton. The same night two parties from the castle [Windsor] came to see the comet, and during the whole month my brother had not an evening to himself. As he was then in the midst of polishing the forty-foot mirror, rest became absolutely necessary after a day spent in that most laborious work; and it has ever been my opinion, that on the 14th of October his nerves received a shock of which he never got the better afterwards; for on that day (in particular) he had hardly dismissed his troop of men, when visitors assembled, and from the time it was dark till past midnight he was on the grass-plot, surrounded by between fifty and sixty persons, without having had time for putting on proper clothing, or for the least nourishment passing his lips.
"February 6th, 1807.—When I came to Slough to assist my brother in polishing the forty-foot mirror, I found my nephew[3] very ill with an inflammatory sore throat and fever.
"February 9th.—Still very ill; and my brother obliged to go on with the polishing of the great mirror, as every arrangement had been made for that purpose.—Mem. I believe my brother had reasons for choosing the cold season for this laborious work, the exertion of which alone must put any man into a fever, if he were ever so strong.
"February 10th.—From this day my nephew's health kept on mending.
"February 19th.—My nephew mending, but my brother not well.
"February 26th.—My brother so ill that I was not allowed to see him, and till March 8th his life was despaired of; and by March 10th I was permitted to see him, but only for two or three minutes, as he was not allowed to speak.
"March 22nd.—He (Sir William) went for the first time into his library, but could only remain for a few moments."
Afterwards Sir John Herschel.