"Paul Hyett" wrote:

Well, the full list of observations are : Barometer, Attached
Thermometer (attached to the barometer I assume), External Thermometer,
Rain Gauge. For the first two, there are morning & evening readings, and
max/min for the ext.thermometer.

When were thermometers that logged max/min temperatures invented,
anyway?


FYI, the 'external temperature' readings for the first several weeks of
Jan 1840 :
Max Min
01/01/1840 53 50
02/01/1840 50 40
03/01/1840 49 41
04/01/1840 48 41
05/01/1840 41 36
06/01/1840 38 28
07/01/1840 38 27
08/01/1840 32 20
09/01/1840 32 22
10/01/1840 37 33
11/01/1840 35 31
12/01/1840 39 32
13/01/1840 46 33
14/01/1840 43 38
15/01/1840 50 43
16/01/1840 49 41
17/01/1840 45 40
18/01/1840 44 32
19/01/1840 50 39
20/01/1840 52 41
21/01/1840 53 41
22/01/1840 50 44
23/01/1840 54 40

I don't know if anyone here has access to data from another English
location during this period, to see whether they sound reasonable.
--
Gives a mean for 1st-23rd of about 4.7°C. The CET for
Jan 1840 is 4.1°C, so, with an element of caution 'cos we
don't know what the rest of the month was like, they look
OK. The ranges between mild and cold spells and between day
and night look OK too.

The principle of the max-min thermometer dates back to
James Six who produced them (commercially?) in the late-18th
century, though the form was rather different from those you
can buy in garden-centres today, and they were pretty
unreliable.

The individual minimum thermometer with an index was
developed around 1790, and the maximum thermometer with
an interrupted mercury column first appeared in 1832. There
were also various, mostly unsatisfactory, instruments which
claimed to do the job before these dates.

Philip