of the Line of the Second Order. 31 
nates of transformation, to obtain the several values required 
by the proposition. 
It may be remarked that the coordinates x,y, are only con- 
nected by a single equation, that of the parabola; and hence 
another condition might be introduced, some one perhaps 
which would usefully simplify the results. Several such may 
be suggested; as for instance, 2, y, to be such a point in the 
curve as should render P a minimum: but this is not the 
proper place for such details. 
Postscript, 
I take this opportunity (the earliest and the most proper 
one that has occurred) of correcting a mistake into which 
Professor De Morgan has fallen with respect to the author- 
ship of a paper on the works of Alexander Anderson, which 
was published in the ‘ Ladies’ Diary’ for 1840 (Companion to 
the Almanac, 1843, p. 9.). That paper was written by my 
late friend Dr. Gregory, and not by me, as stated in the place 
referred to. It was, Iam pretty sure, the very last dissertation 
he ever published. Jam the more anxious to disclaim it early, 
as the authority of Mr. De Morgan would otherwise render 
it a matter of history, and I am by no means desirous to have 
the works of other geometers, however valuable, ascribed 
to me. 
Whilst I am on this subject, I have to correct a mis-state- 
ment of my own in the Philosophical Magazine for August 
last. I had attributed the theorem of which I there gave a 
demonstration to Dr. Wallace, mainly on his own authority. 
I have since found that the same theorem had been given 
about thirty years earlier by Lambert (in his Insigniores orbite 
cometarum proprietates, section i.), together with the other 
theorems published in the ‘ Mathematical Repository’. (Pon- 
celet, Traité de Propriétés Projectives, p. 268.). 
It may also be worth noticing, that amongst the foreign 
proofs of Pascal’s Hexagram, I have found since my own was 
printed (Phil. Mag., July 1842.), two very elegant ones, which 
deserve to be known in this country; one by Magnus in Crelle’s 
Journal, which is copied into the ‘ Ladies’ Diary’ for 1843; 
and the other by Levy in ¢om. iv. Quetelet’s Correspond- 
ence, p.24. Five others also are given in the ‘ Diary’ by 
English writers. 
Royal Military Academy, Dec. 3, 1842. 
