which the study of Quaternions was making abroad. Especially did the
subject attract the attention of that accomplished mathematician,
Moebius, who had already in his "Barycentrische Calculus" been led to
conceptions which bore more affinity to Quaternions than could be
found in the writings of any other mathematician. Such notices of
his work were always pleasing to Hamilton, and they served, perhaps,
as incentives to that still closer and more engrossing labour by
which he became more and more absorbed. During the last few years of
his life he was observed to be even more of a recluse than he had
hitherto been. His powers of long and continuous study seemed to
grow with advancing years, and his intervals of relaxation, such as
they were, became more brief and more infrequent.

It was not unusual for him to work for twelve hours at a stretch.
The dawn would frequently surprise him as he looked up to snuff his
candles after a night of fascinating labour at original research.
Regularity in habits was impossible to a student who had prolonged
fits of what he called his mathematical trances. Hours for rest and
hours for meals could only be snatched in the occasional the lucid
intervals between one attack of Quaternions and the next. When
hungry, he would go to see whether any thing could be found on the
sideboard; when thirsty, he would visit the locker, and the one
blemish in the man's personal character is that these latter visits
were sometimes paid too often.

As an example of one of Hamilton's rare diversions from the all-
absorbing pursuit of Quaternions, we find that he was seized with
curiosity to calculate back to the date of the Hegira, which he found
on the 15th July, 622. He speaks of the satisfaction with which he
ascertained subsequently that Herschel had assigned precisely the