our friend and host on May 5, three weeks before
the final catastrophe, of which he wrote me a graphic description.
As the barricades were stormed by MacMahon, the Communist line of
retreat was through the region of the observatory. The walls of
the building and of the yard were so massive that the place was
occupied as a fort by the retreating forces, so that the situation
of the few non-combatants who remained was extremely critical.
They were exposed to the fire of their friends, the national troops,
from without, while enraged men were threatening their lives within.
So hot was the fusillade that, going into the great dome after the
battle, the astronomer could imagine all the constellations of the
sky depicted by the bullet-holes. When retreat became inevitable,
the Communists tried to set the building on fire, but did not succeed.
Then, in their desperation, arrangements were made for blowing it up;
but the most violent man among them was killed by a providential
bullet, as he was on the point of doing his work. The remainder
fled, the place was speedily occupied by the national troops, and
the observatory with its precious contents was saved.

The Academy of Sciences had met regularly through the entire Prussian
siege. The legal quorum being three, this did not imply a large
attendance. The reason humorously assigned for this number was that,
on opening a session, the presiding officer must say, _Messieurs,
la seance est ouverte_, and he cannot say _Messieurs_ unless there
are at least two to address. At the time of my visit a score of
members were in the city. Among them were Elie de Beaumont, the
geologist; Milne-Edwards, the zoologist; and Chevreul, the chemist.
I was surprised to learn that the latter was in his eighty-fifth
year; he seemed a man of seventy or less, mentally and physically.
Yet we little thought that he would be the longest-lived man of equal
eminence that our age has known. When he died, in 1889, he was nearly
one hundred and three years old. Born in 1786, he had lived through
the whole French Revolution, and was seven years old at the time of
the Terror. His scientific activity, from beginning to end, extended
over some eighty years. When I saw him, he was still very indignant
at a bombardment of the Jardin des Plantes by the German besiegers.
He had made a formal statement of this outrage to the Academy of
Sciences, in order that posterity might know what kind of men were
besie