Dungal, like the two others named above, was an astronomer. He
probably belonged to Bangor, and left his native land early in the
ninth century. In 811 he wrote a remarkable work, _Dungali Reclusi
Epistola de duplici solis eclipsi anno 810 ad Carolum Magnum_. This
letter, which is still extant, was written at the request of
Charlemagne, who considered its author to be the most learned
astronomer in existence and most likely to clear up the problem
submitted to him.

Before passing to the next period, a word should be said as to the
medieval physicians, often if not usually belonging to families of
medical men, such as the Leahys and O'Hickeys, and attached
hereditarily to the greater clans. These men were chiefly compilers,
but such works of theirs as we have throw light upon the state of
medical knowledge in their day. Thus there is extant a treatise on
_Materia Medica_ (1459); written by Cormac MacDuinntsleibhe
(Dunleavy), hereditary physician to the clan of O'Donnell in Ulster.
A more interesting work is the _Cursus Medicus_, consisting of six
books on Physiology, three on Pathology, and four on Semeiotica,
written in the reign of Charles I. of England by Nial O'Glacan, born
in Donegal, and at one time physician to the king of France.

O'Glacan's name introduces us to the middle period, if indeed it does
not belong there. _Inter arma silent leges_, and it may be added,
scientific work. The troublous state of Ireland for many long years
fully explains the absence of men of science in any abundance until
the end of the eighteenth century. Still there are three names which
can never be forgotten, belonging to the period in question. Sir Hans
Sloane was born at Killileagh, in Ulster, in 1660. He studied
medicine abroad, went to London where he settled, and was made a