July 31.] 
THE COTTAGE GARDENER. 
271 
of 30° the mean temperature is 70°; at 40°, 63° ; at 50°, 
50°; at 60°, 40°. In America, or tlie New World, the 
temperature is lower, ranging from 3° less at the lati¬ 
tude of 30° to some 12° or 14° less at the latitude of 00°. 
There is also a difference in the temperature of the 
northern and southern hemispheres in the same lati¬ 
tudes, the northern being warmer in summer and colder 
in winter, and the southern being cooler in summer and 
warmer in winter. A temperature too high is just as 
fatal to a plant as one too low; the growing of wheat at 
the level of the sea in the tropics would be equally 
successful with the growing of palms in the open air in 
England, though from different causes. Our correspon¬ 
dent who made the enquiry about Cape shrubs, last 
week, will at once perceive that between the colony and 
his position there may be some 17° of latitude, without 
even noticing that he is situated in a different hemi¬ 
sphere, also that the medium temperature at the Cape 
will he about 05°, while where he lives it may be less 
than 50°; and this is not all, for while the difference 
between the highest and lowest temperature at the Cape 
will not greatly exceed 12° the difference in bis or her 
garden will be nearer 28°, and frequently a great deal 
more. Thus, it is no uncommon thing to see the ther¬ 
mometer in the shade, in England, at 80° in summer, 
and as low, and lower, than 20° in winter. In rearing 
exotics, therefore, the mean temperature of the year, or 
even of every month in the year, is of far less moment 
than the ascertaining, Secondly, what is the highest and 
lowest temperature to which a plant is naturally sub¬ 
jected. So far as this goes, there is a great deficiency of 
information, but much will, ere long, be done to remedy 
it. In our climate, other things being equal, one degree 
of latitude is nearly synonymous with one degree of 
temperature. In insular situations, the summers are 
cooler and the winters warmer, though the mean tempe¬ 
rature of the year may be nearly similar to what is seen 
in similar latitudes in the middle of a continent. Thus, 
though Vienna be three degrees nearer the equator than 
London, there is very little difference in the mean 
temperature, but the summers are hotter and the winters 
colder, and, therefore, many fruits will ripen there; 
whilst, on the other hand, shrubs will thrive here which 
would be destroyed there. In Cornwall, again, where a 
misty vapour hangs over it, by being so nearly sur¬ 
rounded by sea, there is such a mild climate, that 
myrtles and hydrangeas flourish out of doors in winter, 
which would be killed in a similar latitude on the 
continent; but in the latter much better fruit could be 
obtained than by possibility could be ripened in the 
mistier atmosphere of Cornwall. The temperature at 
Quito, in Peru, some eight thousand feet above sea 
level, though beneath the equator, is somewhat similar 
to the temperature of France, when the mean of the 
year is taken, and yet many plants flourishing in Quito, 
would be killed out of doors in France, because there 
the thermometer sinks often to 23°, while at Quito, the 
temperature partaking of the equability of the tropics 
seldom falls to 40°. The firmness of texture imparted 
to plants from a high temperature, and a clear atmo¬ 
sphere in summer, enables them to bear a degree of 
cold which they would not do with us, because we 
cannot command the bright sunlight of such a summer. 
There is a most valuable paper by Dr. Lindley, on the 
temperature to which plants in New Holland are ex¬ 
posed, in the number of the journal referred to. The 
low temperature indicated by the thermometer at sun¬ 
rise would be a surprise to many. We could only trust 
such plants in such a temperature here, after being able 
to give them the clear dry atmosphere, and high tempe¬ 
rature of a New Holland summer. Thirdly. Altitude 
must be taken in connection with latitude ; and here, in 
many respects, our information is limited, though few 
things could be more important. The matter of 500, or 
1000 feet elevation, is of consequence even in our own 
island. As heat decreases from the equator to the Poles, 
so also does it decrease from the surface of the earth to 
the highest experimented-upon limit of our atmosphere. 
Some of the notes of Mr. Green, the veteran balooner, 
are in this respect most interesting. The decrease was 
gradual for the height of ten thousand feet, after that 
most rapid. It has been said that rising in altitude 
000 feet reduces the temperature as much as the distance 
of one degree of latitude from the equator. This is, 
however, far from being generally correct. Measuring 
from the level of the sea into the air, we come to a point 
where the moisture in the atmosphere remains congealed 
in ice or snow. At the equator, this point is at the 
height of 15,000 feet; at 35° north latitude, it is 11,000 
feet; at 45°, it is 8400 feet; in the 50th degree, 0000 
feet; in the 60th degree, 3000 feet; and in the 70th 
degree, from 1200 to 2000 feet. Taking these facts into 
consideration, we come to the conclusion, that the 
altitude sufficient to lower the temperature equal to one 
degree of latitude, will depend upon the distance of that 
degree of latitude from the equator, and other considera¬ 
tions, such as insular and continental, northern or 
southern hemisphere. According to Decandolle, heat 
decreases in France at the rate of one degree of latitude 
to 540 feet of altitude. But Humboldt states, that 
in the middle of the temperate Zone, heat decreases 
in the ratio of one degree of latitude for 300 feet 
of altitude. No certain data, no progressive ratio, 
that I am aware of, has yet been demonstrated. We 
shall not go greatly wrong if, on ascertaining the alti¬ 
tude of a place, we reckon 600 ft. of altitude at the 
equator, 500 ft. at the extremity of the tropics, lat. 23£°, 
400 ft. at the latitude of 30°, 350 ft. at 40°, and 300 ft. 
at the latitude of 50°, as equal to the lowering of the 
mean temperature of the year, by the recession of one 
degree of latitude from the equator. It has also been 
said, that plants flourishing within the tropics at the 
height of 7000 feet, ought to flourish in the climate of 
England; but this should be adopted with the reservation, 
that even at a high altitude within the tropics, the ele¬ 
vation is distinguished for equability, and, consequently, 
there is not the difference between the hotter and colder 
seasons as there is with us. The farther we recede from 
the tropics, this difference becomes more striking, and 
is seen more upon continents than islands. This chang¬ 
ing of climate with altitude, gives to the tropics a gran¬ 
deur and variety, of which we who have not seen them 
can form but an inadequate conception. There, in the 
plain near the sea-level, flourish the Banana, the Palm, 
and the Cocoa-nut; at a higher elevation, will be found 
trees and shrubs, which, instead of a warm stove, will 
flourish with us in ordinary greenhouses; while at an 
altitude of from 7000 to 8000, and 9000 feet, may 
be cultivated with success the fruits and corn of our 
own climates. At such altitudes, where in our lati¬ 
tudes existence would be next to impossible, owing 
to the coldness and rarity of the atmosphere, are 
placed some of the finest cities of Spanish America. 
Fourthly. Several other characteristics of the climates of 
exotic plants deserve mentioning, but our space is filled. 
General as the remarks have necessarily been, they will 
in some measure be a guide to the receivers of plants 
and seeds from abroad, who have hitherto paid no atten¬ 
tion to the subject. Amateurs, by attending to the 
subject, would soon be able to enlighten us in return 
for our practical lessons. One more characteristic we 
merely mention. The difference of mean annual tem¬ 
perature on the east and west sides of our continents. 
For instance, barley will ripen well frequently in Nor¬ 
way, at the 70th degree of north latitude, but in Russia 
it seldom ripens beyond the 60th, while on the eastern 
shores of America, it is said that wheat can scarcely be 
grown beyond the 53rd degree of latitude. There is a 
