1816. ] during the Year 1815, 67 
to its radiating power ; and that those bodies upon which dew falls 
are many degrees (from 14° to 20°) colder than the atmosphere. 
. Hence the cause of the deposition of dew is obvious. Heat is 
radiated from those bodies on which it falls, they become colder 
than the atmosphere; the aqueous vapour in the air is in conse- 
quence condensed and deposited upon them. 
2. It is well known that, in islands, neither the cold of winter nor 
the heat of summer is so violent as on continents in the same lati- 
tude, or even situated nearer the equator, The surrounding sea 
moderates both the winter cold and the summer heat, and makes 
the temperature approach more nearly to a mean. If the islands 
be of small size it it no uncommon thing for the winter to pass, 
even in high latitudes, without any frost: this is often the case in 
the Orkney and Shetland Islands to the north of Scotland. Snow 
seldom falls upon them, and searcely ever lies for any considerable 
time ; but to balance the mildness of the winter, the summer is 
much colder than it is upon the continent in the same, or even in 
much higher latitudes. For example, at Stockholm, nearly in the 
sixth degree of north latitude, nightingales are seen, which shows us 
that the summer for some months is warmer than at York; but the 
winter is so severe that neither the chesput-tree nor the furze can 
resist it, though these plants thrive very well in the northern parts 
of Great Britain. After these remarks the reader will not be sur- 
prised that in Iceland there was no frost in the southern part of the 
island after the beginning of January, 1814. (Annals of Philosophy, 
vol. vi. p. 395.) 
3. The following table exhibits the mean temperature of every 
month, at Plymouth, Sidmouth, and at Tottenham in the neigh- 
bourhood of London, according to the tables published in the 
Annals of Philosophy. The fourth and fifth columns show the 
temperature at Somerset House, and on the Frith of Tay in 
Scotland. 
Plymouth, | Sidmouth, |Tottenham. London, |Kinfaun’s Castle, 
—- 
— 
January ........ 31 26°T 28°8 25°39 
February ...... 38 29°6 35°6 34°50 
Maren se. i, 40°5 37°8 37-5 36:80 
APTS oh “515 50-7 50'3 46°10 
ON apn eee 52°5 504 518 A4*TT 
LT Se eee 590 54-0 56°5 50°50 
PUN es > o oste aoe. 61°5 62°38 64 57°10 
August...../.... 610 58 61°6 54°86 
September .,,... 575 54 575 52°66 
(Oot) 470 A6'8 A9*5 A451 
“November ...:.. 41-0 36°5 AQT 38:16 
December ...... 42°5 396 | 42:6 35°38 
—— a eed i = ee ———— a ee eee 
Mean " 48°2 A7°2 A48°2 43 39 
7a a ee nadia 
From this table it appears that Plymouth was warmer during the 
year 1814 than either Sidmouth or London. It is generally believed 
that the summers in the neighbourhood of London are warmer than 
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