98 
which they are the organs of reproduction must have con- 
tributed very largely to tlie production of such beds of coal. 
They doubtless were floated in water with other vegetable 
remains to the places where they are now found, and owing 
to their coriaceous covering have been preserved whilst 
their accompanying plants have only left traces of their 
remains in the black charcoal dispersed throughout the 
shale. The macrospores are compressed, but their upper 
surfaces are minutely tuberculated, and their under ones 
marked by a tri-radiate ridge. They yet contain sufficient 
combustible matter to afford a brilliant flame in a burning 
candle. 
Ordinary Meeting, March 9th, 1875. 
Edwakd Schunk, Ph.D., F.RS., President, in the Chair. 
“On Mr. Millar’s Method of finding the Axes of an 
Ellipse when two conjugate diameters are given,” by 
Robert Rawson, Esq., Honorary Member of the Society. 
At the ordinary meeting of the Society, February 9th, 
1875, Professor 0. Reynolds communicated a paper on “A 
Method of finding the Axes of an Ellipse when two conju- 
gate diameters are given,” by J. B. Millar, B.E. 
Of this solution of an ancient and useful problem it is 
necessary to observe that it is accurate, simple, but not 
new. 
It may be found in Waud’s Algebraical Geometry, art. 290, 
page 139. The construction here referred to is the same as 
that employed by Mr. Millar, with the exception of the 
generating circle OKEF, which, however, is not necessary 
in the construction of the principal axes. Waud’s solution 
depends upon the well known property, viz., the equal areas 
of all parallelograms whose diagonals are conjugate diame- 
ters in position and magnitude. 
