Fol. 192
Hond Sr Upminster 13 Feb: 1730/1
The late Frost having been almost as in-
tense as any that hath been for many years, I send
you my Account of it: wch if you think worth the cogni-
zance of the R.S. be pleased to impart it to them.
In the Philos: Transact: for Novr. & Decr. 1709
326. I have given an Account of some of the
most remarkable Frosts, that I could fin any
relation of, & particularly of that great and
I had almost said universal one in 1708, wch
the Soc. had very good Histories of from divers
parts, & wch, in that Transactions, I have given an
account of from the original Papers, wch the Soc-
iety as pleased to do me the honr to entrust me wth.
In that Trans: I have made it very pro-
bable, yt the greatest Descent of the Spirits in
the Thermometer, was on Decr 30 1708, when
y Glass was within one tenth of an inch
low as it is wth Artificial Freezing with
now or Ice & Salt. And in the late Frost
was almost, if no altogether, as low.
The Freezing-Point of my Thermometer
Is 10 inches (wch I call 100 degrees) above the Globe
of Spirits; & the most intense Freezing (ac-
cording to the methods I have mentioned in
at Transaction) is just at, or very little
within the Ball. And on Jan. 30 about Sun-rising
the Thermometer was but an inch, or 10gr above
the point of extreme Freezing; & on Febr. 3,
at only half an inch, or 5gr. And considering that
Fol. 193
the Thermometer I observed with in 1708, was
much less accurate, & differenlt graduated from
that wch I now have, I am apt to think, that the
Frost on Feb. 3 last, was altogether as intense
as yt on Dec 30 1708. For although a Frigori-
fick Mixture sunk the Spirits but one tenth
lower in the Old Thermometer, & about 5 or 6
tenths in that I now observe with, yet I take
the Difference to be little, or none at all, by
reason of the tenderness of the New above the
Old Glass.
And this degree of Cold, I take to be as ex-
cessive, as in any of the years mentioned in the
said Transactions; yea any of the Years, what
the Thames at London was frozen over: I am
sure than in the year 1716, when that River
was frozen over for several miles, and Booths
& streets were made on the Ice; an Ox roasted there-
on, &c. For the lowest point of Freezing in
1716 was on Jan 7, when the Spirits fell to 35gr on-
ly of the Glass I now make use. But the true
cause of the Freezing of the Thames yt year,
was not barely the Excess of the Cold, but ye
long continuance of it. Which also was the
principal cause of those remarkable Congela-
tions of yt River in 1683, & 1708, when I saw
coaches driven over the Ice, large Fires
made on it, &c.
I am wth great respect
Hond Sr Yours
Wm Derham
I have just rigged up & tryed
the Reflecting 8 foot Telescope I
had of Mr Molyneuxes grinding, & find it admirable.
Derham was a Church of England clergyman and a natural philosopher, interested in nature, mathematics, and philosophy. He frequently requested medical advice from Sloane, and likely served as a physician to his family and parishioners (Marja Smolenaars, Derham, William (16571735), Oxford Dictionary of National Biography, Oxford University Press, 2004 [http://www.oxforddnb.com/view/article/7528, accessed 7 June 2011]).
