A circle is an ellipse in which the two Foci have been brought together.
"A Text-Book of Astronomy"
George C. Comstock
It appears from the figure that during this time the one star has gone completely around the other, as a planet goes around the sun, and the true orbit must therefore be an ellipse having one of its Foci at the center of gravity of the two stars.
"A Text-Book of Astronomy"
George C. Comstock
Later, there would have been great loss of life in the streets, and the more numerous Foci of conflagration would have burned the city in one day instead of four, and made things vastly worse.
"The Letters of William James, Vol. II"
William James