lliwell in his _Rara Mathematica_--not a
fac-simile, but a rule and type representation of it, ciphers being used
by him for the circles in the original. Mr. Halliwell gives it without
note or remark; and evidently had not divined its meaning. This was
done, however, soon after in a review of Mr. Halliwell's book in the
_Philosophical Magazine_. I am not able at this moment to refer to
either, so as to give exact dates: but is was somewhere from 1838 to
1840.

Perhaps, however, I am giving "E.V." information that may be irrelevant
to his purpose; though it may of some use to another class of inquirers.
I proceed, therefore, to one or two notices that seem to have a more
direct bearing on his object:

1. Chasles' _Apercu Historique sur l'Origine et le Developpement de
Methodes en Geometrie_; passim, but especially in note xii.: 4to.,
Bruxelles, 1837.

2. Chasles' several notices in _Comptes Rendus des Seances de l'Acad.
des Sciences._ All subsequent to the "Apercu."

His _Catalogue des Manuscrits de la Bibliotheque de Ville de Chartres_
should also be consulted, if accessible to "E.V." Copies of it, however,
are very rare in the country, as it was privately printed and never
published. If, however, your correspondent have any serious inquiry in
view which should render his consultation of it desirable, I can put it
in his power to do so personally through you.

3. Libri, several notices in the same series of papers.

4. Libri, _Histoire des Sciences Mathematiques en Italie_. Several
places. Bactulica. Paris, 1838-1841. 4 tomes. 8vo.

5. Peacock (Dean of Ely), "Arithmetic," in the _Encyclopaedia
Metropolitana_. This is now, I believe to be had either separately, or
in the volume devoted to pure "Mathematics."

6. De Morgan, _Penny Cyclopaedia_ in loc., and occasionally elsewhere in
the work.

7. Leslie's _Philosophy of Arithmetic_.

8. Humboldt, in a paper which is translated in the _Journal of the Royal
Institution_, vol. xxix.

I believe a good many other references might be made, with little
trouble, to foreign Memoires; and (perhaps still more to your
correspondent's apparent purpose) to some amongst the Memoires that
relate to inscriptions and topography, rather that amongst those
relating directly to science or literature. However, the two parts of
the subject cannot be effectively studied separately from each other;
and I am not without a hope that these straggling notes may be of some
use to "E.V."