invisible state, and one-tenth per hundred of carbonic acid gas, and several local compounds. The 
proportions of oxygen and azote have never been known to vary. It is the stability of these gases 
that enables both the animal and vegetable Idngdoms to flourish ; for an alteration in their proportions 
would cause universal destruction. 
The height of our atmosphere is a question much disputed : — M. Biot conceives it to be 18 miles. 
Sir John Lubbock scarcely 22i miles, some extend it to 50, others to 80, and Dr. Dick to 200 miles. 
The great meteor of February 11, of the present year (whose path was so beautifully traced by James 
Glaisher, Esq., of the Royal Observatory) when fh-st seen in the north of England, was at a height of 
90 miles above the earth's surface, finally bm-sting in Bedfordshire, at an elevation of 23^ miles; yet 
the noise resulting from the explosion was so loud as to be heard at the distance of 100 miles, not only 
proving that the body was of great size,* but that the atmosphere must have extended beyond this 
ele%'ation ; however, as our atmosphere rapidly decreases in density upwards, om- highest clouds floating 
in an air of only two-thii'ds the density of that at the sea level, and as vegetation cannot exist in such 
a rarified medium, it is unnecessary to linger on this subject, which is one likely to be doubtful for 
some time. 
The pressm-e of the atmosphere is the combined weight of gases, and the elastic force of vapour 
contained in the air. If the gaseous atmosphere were destroyed, there would yet be an aqueous 
atmosphere, although life would under these circumstances be extinguished. This atmosphere of water 
in hot countries would be held in the condition of invisible vapour-, consequently those skies would be 
cloudless ; but, as we approached colder regions, clouds would appear, and in the temperate (in which 
England is included) and polar regions there would be incessant rain or snow. There is one remark- 
able difference between the gaseous or di-y air and vapom-ous or wet air ; the dry air flows from the cold 
to the warm regions, and the wet air from the warm to the cold. These two atmospheres are well 
mingled together, and are borne along to great distances ; and the latter is only precipitated in the form 
of rain, hail, or snow, when an atmosphere is entered which is much colder than that which involves 
them. By calculation we are enabled to separate the weight of dry air from that of moist air ; 
from which we find that with the mean height of the barometer in round numbers at 29 j inches, 29 
of this will be dry air, and half an inch wet aii'. 
There are wonderful properties of the atmosphere constantly at work for the benefit of the vegeta- 
tion of the world, some of which are now to be sho'svn.t The carbonic acid we are exhaling, in a few 
short hom's will be travelling along to the north and to the south of us, endeavouring to traverse the 
world. The Cedars of Lebanon, the Ai'aucarias of the Andes, and the beautiful Pines of the Himalaj^as 
will take of it to increase theii' size ; the Date trees of the valleys of the Nile will drink it in by their 
leaves ; the Cocoa-nuts of Tahiti, and the Mangoes of the Amboyna Islands wOl ripen upon it ; the 
Ericas of the Cape, the Cacti of the New World, and the Orchidaceous plants of the Indian Archipe- 
lago will change it into flowers. The oxygen we are inhaling has been but lately distilled for us by 
the jNIagnolias of the Susquehana and the Passifloras of Texas. The huge Rhododendrons of the 
Himalayas, the Cinnamon trees of Ceylon, and the Roses of Cashmere, with forests older than the 
Flood, bui'ied deep in the heart of Africa, have contributed to it. The rain we see falling around us 
was thawed from the mountainous icebergs of the polar seas; and aquatic plants have sucked up fi-om 
the Nile, the Mississippi, and the Tigris, and exhaled as vapours the mighty snow-fields of the Andes, 
the Atlas, and the Alps. 
* Mr. Glaisher calculates it to be three-quarters of a mile in circumference. 
+ It is proper to state that the substance of this illustration has been enlarged from some beautiful ideas which appeared in the 
Quarterly Itevlew. 
3JIisrtllniitntis Untte. 
Disease in Fears, ^o. — The pistillary necrosis, men- 
tioned in the work which is in the course of translation 
in the Gardeners' Olironiclc (January oth, 1850), is a dis- 
ease of great importance and interest to the cultivators 
of Pears, Apricots, Peaches, &c., and also to those who 
are engaged in making experiments for the producing 
new varieties. I am not aware that the natine of this 
disease has been ascertained with reference to these 
pouits : the pistil in the flowers of the fruits I have 
mentioned is veiy apt to be injured in early seasons by 
fi'osts, when the blossom is opened, and even before it 
is opened : the pistil is not so protected as the male 
organs, and the shape of the corolla iu the Pear will 
afford less protection to the organs of fructification 
than is found in the Apricot, Peach, or CheiTy ; hence 
the greater uncertainty of the crop of Pears than is the 
case with the other fruits. 
The author of the work I have referred to, oh- 
I) 
''^ 
