ian researches. It is
indeed certain that, if the reckoning by heliacal risings of Sirius
did not begin in 1322, we must go nearly 1460 years back for its
origin; since it must have been adopted when that event preceded
only for a short time the annual inundation of the Nile. But,
according to some, the year 1322 A.C. fell during the reign of
Sesostris, to whom Herodotus ascribes several regulations connected
with the rising of the Nile. Certainly, 2782 A.C. is a more remote
era than we are hitherto warranted to assume for any astronomical
observation.

Believe me, dear Mrs. Somerville,
Very truly yours,
HENRY HALLAM.

I refer you to Montucla, if you have any doubt about the Egyptian
year being of 365 days without bissextile of any kind.

* * * * *

I had sent a copy of the "Mechanism of the Heavens" to M. Poisson soon
after it was published, and I had received a letter from him dated 30th
May, 1832, advising me to complete the work by writing a volume on the
form and rotation of the earth and planets. Being again strongly advised
to do so while in Paris, I now began the work, and, in consequence, I
was led into a correspondence with Mr. Ivory, who had written on the
subject, and also with Mr. Francis Baily, on the density and compression
of the earth. My work was extensive, for it comprised the analytical
attraction of spheroids, the form and rotation of the earth, the tides
of the ocean and atmosphere, and small undulations.

When this was finished, I had nothing to do, and as I preferred analysis
to all other subjects, I wrote a work of 246 pages on curves and
surfaces of the second and higher orders. While writing this, _con
amore_, a new edition of the "Physical Sciences" was much needed, so I
put on high pressure and worked at both. Had these two manuscripts been
published at that time, they might have been of use; I do not remember
why they were laid aside, and forgotten till I found them years
afterwards among my papers. Long after the time I am writing about,
while at Naples, I amused myself by repairing the time-worn parts of
these manuscripts, and was surprised to find that in my eighty-ninth
year I still retained facility in the "Calculus."

The second edition of the "Physical Sciences" was dedicated to my dear
friend, Sir