AESTIVATION. 
they are sold under the name of scarlet-flowered 
horse chestnuts, the only really scarlet-flowered 
variety at present known is that called Whit- 
ley’s fine scarlet, and recently introduced from 
America. ‘Two well-marked varieties of the yel- 
low-flowered horse chestnut are known. ‘The 
American horse chestnut is a very good sort, with 
red or pink flowers; the variegated-flowered, is 
a desirable kind; and the long-spiked flowers 
freely, and is a compact and erect grower. 
A group of ornamental shrubs or small trees 
shares with the esculus the more general botanic 
| name of Hippocastanee, or plants of the horse 
chestnut family ; and, though now made a separ- 
ate group or genus of that family under the name 
of Pavia, they formerly shared even the generic 
name of zesculus, and were popularly called scar- 
let horse chestnuts. These shrubs grow to the 
| height of about 16 or 18 feet; their growing 
shoots in summer are of a reddish hue; their 
leaves are palmated, and somewhat similar to 
those of the <esculus, but smaller; and their 
_ flowers bloom from April till about the middle of 
_ June, are of a bright red colour, and continue in 
succession during upwards of six weeks. The 
principal species or varieties of the Pavia—some- 
| times popularly called the Buck’s Eye Tree—are 
seven in number, and designated rubra, carnea, 
humilis, hybrida, flava, neglecta, and macrostachya. 
—Treatise on Planting in Library of Useful Know- 
ledge.—Marshall on Planting —Miller’s Gardener’s 
Dictionary.—Loudon’s Gardener's Magazine, vol. 
ii.— The Gardener's Chronicle, 1843.— Loudon’s 
Hortus Britannicus. 
AESTIVATION. The flowering or summer 
condition of plants; as vernation or leafing is 
their spring condition, ripening or fructification 
is their autumn ccndition, and sleeping or hyber- 
nation is their winter condition. 
AUTHIOP’S MINERAL. The black sulphuret 
of mercury. It is occasionally used as an alter- 
ative in cases of mangy affections in any of the 
animals of the farm, and in cases of surfeit or 
foulness of skin in the horse. The dose of it is 
three drachms daily for the horse ; and an accom- 
panying dose of four drachms of cream of tartar 
is advantageous. 
AETHRIOSCOPE. A recently invented in- 
strument for detecting and indicating pulsations 
or sudden streams of altered temperature in the 
atmosphere. Pulsations or dartings of heat up- 
ward from the earth to the higher regions of the 
atmosphere, and of cold downward from the higher 
regions of the atmosphere to the earth, are now 
believed to be a distinct phenomenon in meteor- 
ology, and to possess a very intimate connexion 
with changes of weather, and particularly with 
the fall of dews ; and as they are undetected by 
our ordinary weather-glasses, and unindicated by 
all our other means of prognostication, an instru- 
ment which shall really detect and measure them, 
promises to be of considerable value to the far- 
mer. The aethrioscope, however, has not yet been 
AEKTHRIOSCOPE. ol 
sufficiently tried to establish confidence in its 
powers ; and even if in principle a successful in- | 
vention, it will probably admit of material im- 
provement. The following somewhat florid ac- 
count of it, taken from the article ‘ Climate’ in 
the seventh edition of the Encyclopedia Britan- 
nica, rather speculates as to what an improved 
instrument may effect, than states what the pre- 
sent instrument has actually accomplished ; and 
is introduced here less for the sake of what it 
says respecting the instrument itself, than for 
sake of the notice which it contains of the pulsa- 
tions of the atmospheric temperature. “ The 
aethrioscope opens new scenes to our view. It 
extends its sensations through indefinite space, 
and reveals the condition of the remotest atmo- 
sphere. Constructed with still greater delicacy, 
it may perhaps scent the distant winds, and de- 
tect the actual temperature of any quarter of the 
heavens. The impressions of cold which arrive 
from the north will probably be found stronger 
than those received from the south. But the 
facts discovered by the aethrioscope are nowise 
‘at variance with the theory of the graduation of 
heat from the equator to the pole, and from the 
level of the sea to the highest atmosphere. The 
internal motion of the air, by the agency of oppo- 
site currents, still tempers the disparity of the 
solar impressions ; but this effect is likewise ac- 
celerated by the vibrations excited from the un- 
equal distribution of heat, and darted through | 
the atmospheric medium, with the celerity of 
sound. Any surface which sends a hot pulse in 
one direction, must evidently propel a cold pulse 
of the same intensity in an opposite direction. 
The existence of such pulsations, therefore, is in 
perfect unison with the balanced system of aerial | 
The most recondite principles of har- | 
mony are thus disclosed in the constitution of | 
In clear weather, the cold | 
pulses then showered entire from the heavens | 
will, even during the progress of the day, prevail | 
currents. 
this nether world. 
over the influence of the reflex light, received on 
the ground, in places which are screened from 
the direct action of the sun. Hence at all times 
the coolness of a northern exposure. Hence, 
likewise, the freshness which tempers the night | 
in the sultriest climates, under the expanse of an 
almost azure sky. The coldness of particular 
situations has very generally been attributed to | 
the influence of piercing winds which blow over 
elevated tracts of land. This explication, how- 
ever, is not well founded. It is the altitude of 
the place itself above the level of the sea, and not 
that of the general surface of the country, which 
will mould its temperature. A cold wind, as it 
descends from the high grounds into the valleys, 
has its capacity for heat diminished, and conse- 
quently becomes apparently warmer. The pre- 
valence of northerly above southerly winds may, 
however, have some slight influence in depress- 
ing the temperature of any climate. In our 
northern latitudes, a canopy of clouds generally 
— 
