86 
In order to support this undertaking the 
more effectually, an increased number of 
subscribers is most desirable. 
Collections of plants from Chili and 
Juan Fernandez, made by Dr. Bertero, in 
the years 1828—30, are likewise offered 
by the Unio Itineraria: viz., collections of 
two hundred species at £3, or one hundred 
species at 30s., being named either by the 
late Dr. Bertero or Dr. Steudel. They 
will also be supplied with numbers on 
their tickets, and the more exact determi- 
nation of them will afterwards appear in 
the Regensberg Botanical Journal, with 
Which these numbers will correspond. 
Caucasian and American specimens of 
plants at 22s. per hundred ; and collections 
of Caucasian specimens only, to the num- 
ber of one hundred and seventy species, 
at 40s., are still to be obtained. 
COMPARISON BETWEEN THE UP- 
PER, OR TERMINAL LINES OF 
TREES AND SHRUBS IN BRI- 
TAIN, AND THEIR GEOGRAPHIC 
EXTENSION TOWARDS THE 
ARCTIC REGIONS. 
By H. C. Watson, Esq. F. L.S. 
In the extreme South-west of Cornwall, 
the mean annual temperature of the British 
coast appears to rise so high as 52° Fahr.; 
on the South coast of Hants, it may be 
estimated as 51°; and at the mouths of the 
Thames and Severn, as 50°. Hence it 
decreases northwards, until we have it 
scarcely 48° at the mouth of the Forth ; 
and probably it is not more than 45° or 46° 
on the North coast of Scotland. The inte- 
rior of the country, however little elevated, 
has a lower mean temperature than the 
WATSON ON THE DISTRIBUTION 
tude nor altitude can there give a satisfac- 
tory clue to the real temperature.. More- 
over, very little is ascertained regarding 
the decrease of temperature, in proportion 
to height above the sea level. It has been 
stated as 1° for seventy yards, for eighty 
yards, and for ninety yards. (Mag. Nat. 
Hist. VIL 493.) Adopting the medium 
scale of eighty yards, and taking 48° as the 
average temperature of the coast in lat. 
53—56°, and 47° in lat. 57—58°, we find a 
temperature of about 29° for the highest 
point of Scotland, 83° for that of Wales, 
and 35° for that of England. The full 
range of mean atmospheric temperature in 
Britain may therefore be stated at 52—29°, 
In general, it may also be said, that the 
mean temperature of the three coldest 
months (Dec., Jan., Feb.) is 10° below that 
ofthe degrees above. But on the coasts, 
and especially on the western coasts, the 
differences are less; while in the inland 
counties, perhaps (more particularly those 
bordering the Thames, and thence to the 
Trent,) the three winter and three summer 
months are 11? to 13? below or above the 
annualmean. Tothegreatestheightat which 
accurate observations have been made for a 
sufficient period, (Lead Hills,in Lanarkshire, 
at 1,280 feet, ) these g ] lusionshold _ 
good, as to the comparative temperature 
of the seasons ; but the application of them 
to greater altitudes is mere assumption. 
In low situations, the air and earth have 
nearly the same temperature; but in as- 
cending the mountains, the latter is found 
to cool more slowly, probably losing 19 of 
temperature for about one hundred and 
twenty-five yards of ascent. 
As to the humidity of the air and quan- 
tity of rain, both are less on the East than 
on the West side of the island, and, in 
general, both increase about the mountain 
tracts. It is possible that a less quantity 
of rain may fall at great elevations, than in 
the valleys, or on the western declivities of 
the mountains; yet, from the frequency of 
mists, and constant deposition of moisture, 
owing to ascending currents of warm aif, 
the climate is more humid than below. 
The general conclusion to be drawn from 
