crowded parts of towns. The healthiness or ess of the air seems to depend much on the f ozone which is present.

ider next the carbonic acid gas. When a al is set on fire, it burns away until nothing le ash is left behind; or when a candle is continues to burn until the whole is conNow, what has become of the original subthe coal and the candle? It seems to have pletely lost; yet in truth we have not dehe atom of it. We have simply, by burning, t into another and invisible form; but it is ally existent as ever.

e substance of a piece of coal or of a candle is of different elements, one of which is called This element forms one of the main ingrediof which the substance of all plants and aniuilt up. Our own bodies, for example, are in made of it. In burning a bit of coal, therech is made of ancient vegetation compressed ed into stone), or a candle (which is prepared nal fat), we set free its carbon, which goes off O mix with the air. Some of it escapes in the ttle solid particles of soot. at the largest part does not go off in smoke. ile in the act of burning, seized by the oxyhe air, with which it enters into chemical ion, forming the invisible carbonic acid gas. deed, this very chemical union which conwhat we call burning, or combustion. The we prevent the flame from getting access of rops down and soon goes out, because the of oxygen is cut off. All ordinary burning

12. The amount thus supplied is o

tively small, for the quantity of veg substance burnt either by man or r but insignificant, when the whole ma phere is considered. An infinitely I furnished by living air-breathing anin

13. In breathing we take air into it reaches our blood. A kind of burn for the oxygen of the air unites wi the blood; carbonic acid is produced, with the exhausted air which we ex taking the next breath. When we air-breathing animal is continually su acid gas to the atmosphere, we perceiv this source of supply must be.

14. Living plants in the presence the power of abstracting from the car air the carbon of which their framew made. When they die, their decay onethe carbon, which, uniting again with carbonic acid gas, and is carried by rain taken up by the air. All decaying pl which are freely exposed to the air fur gas.

15. Lastly, in many parts of the w in volcanic regions, this same gas is g quantities from the ground. From a sources, then, the atmosphere is con ished with carbonic acid gas, to supply by the enormous demands of the veg

carbon.

ertheless, the quantity of this gas present in ery small compared with the volume of the It has been found to amount to

d oxygen. - ordinary pure air than four parts in every nd of air. Yet this small proportion suffices all the luxuriant growing vegetation of the

ace.

the term water vapor, or aqueous vapor, is invisible steam always present in the air. is familiar with the fact, that, when water t passes into vapor, which becomes invisibly the air.

matter how dry the air may appear to be, ess of this invisible water vapor is always rough it. Every mist or cloud which gathsky, every shower of rain, snow, or hail which e ground, every little drop of dew which at athers upon the leaves, bears witness to its

importance of this ingredient of the atmoshe general plan of our world can hardly be ted. It is to the vapor of the atmosphere we all the water circulation of the land, gs, brooks, rivers, lakes, on which the very nts and animals depends, and without which, we know, the land would become as barren, I lifeless as the surface of the moon. It is, to the changes in the supply of this same but ever present substance, that the rise of storms is largely due.

e quantity of water vapor in the air varies to day, and indeed from hour to hour. It is omparatively small in amount, ranging from

germ, the rudiment or first principle | dis-in-fect'in

of a plant or an animal. in-fin-i-tes/i-mal, infinitely small.

in-gre'di-ent, one of the substances

which goes to form a compound.

ever would mi'cro-scope

amining ob viewed with

The four elements (2), according to the old water, fire, and air," and out of these all corporeal su

XC.-DRACHENFEI

BYRON.

1. THE castled crag of Drachenfel
Frowns o'er the wide and wind
Whose breast of waters broadly
Between the banks which bear
And hills all rich with blosson
And fields which promise corn
And scattered cities crowning
Whose far white walls along t
Have strewed a scene which I
With double joy wert thou wit

2. And peasant girls, with deep-b
And hands which offer early f
Walk smiling o'er this paradise
Above, the frequent feudal tow
Through green leaves lift their
And many a rock which steep
And noble arch in proud deca
Look o'er this vale of vintage

one thing want these banks of Rhine,— gentle hand to clasp in mine!

nd the lilies given to me,

igh long before thy hand they touch
how that they must withered be;
yet reject them not as such;
I have cherished them as dear,
use they yet may meet thine eye,
guide thy soul to mine even here,
en thou behold'st them drooping nigh,
know'st them gathered by the Rhine,
offered from my heart to thine!

river nobly foams and flows,
charm of this enchanted ground,
all its thousand turns disclose
Le fresher beauty varying round:
haughtiest breast its wish might bound
ough life to dwell delighted here;
could on earth a spot be found.
nature and to me so dear,

ld thy dear eyes in following mine
I sweeten more these banks of Rhine!

s in cow), appears dark, | corn, here, grain in general.
threatening.
haugh'ti-est, loftiest; proudest.

=ls (drä'khen-felce) (1), or "Dragon's Rock," rises about a above the Rhine, on its right bank, a few miles up the river On the summit are the ruins of a castle of the twelfth century. Che poet's sister. feudal towers (2), towers built when the prevailed. By the feudal system the vassals held lands of condition of giving him military service.

bear the vine (1); vintage bowers (2).