of the body ; the former constitutes the pulmonic, 
the latter the systemc circulation. Before the 
blood can be employed in the various functions 
of the body, it is necessary for it to undergo a 
certain change, which is effected in the lungs. 
After it has undergone this change, it is brought 
back to the heart, and is again propelled from 
this organ, along the arteries of the systemic 
circulation, to all parts of the body. The arteries 
which perform this office of conveying the blood 
from the heart, are flexible elastic tubes, princi- 
pally composed of membrane, but—as is gener- 
ally supposed—containing also a quantity of mus- 
cular fibres, which give them, to a certain extent, 
| the power of contracting, and consequently of 
propelling their contents. 
ARTESIAN WELL. A flow of water to the 
surface of the earth, from strata situated beneath 
|| the lowest subsoil, through a perpendicular boring 
made with a long auger and rod. It is called 
artesian from the supposition, that the art of 
making it was first known and practised in the 
district of Artois in France; yet it appears to 
have been known in Italy at a very ancient period, 
and it belongs, in modern times, fully more to the 
United States of America than to the old world. 
The artesian well is of great value on farms and 
in districts in which a summer supply of good 
water is scarce; and it has, within a recent period, 
refreshed and enriched many a spot whose soil 
was comparatively infertile with aridity, and 
whose inhabitants suffered unhappiness and dis- 
ease from thirst or from noxious water. Some 
artesian wells have been bored to the depth of 
2,900 feet before a plentiful and permanent flow of 
g. od water has been obtained; and many, at both 
gieat depths and small, have brought up in arid 
districts such copious supplies as have provoked 
the astonishment of all unscientific observers. 
The Abattoir de Grenelle in Paris being at too 
high a level to obtain an adequate supply of water 
by the ordinary means, it was proposed to sink 
an artesian well within the premises, which pro- 
posal having been agreed to, the work was per- 
severingly carried forward through many difficul- 
ties during eight years, until the boring was 
terminated by the auger penetrating the water- 
bearing strata on the 26th February, 1841, when 
a sudden and violent rush of water occurred, 
overflowing at the surface of the ground. As the 
boring progressed, tubes of rolled iron, and sub- 
sequently of copper, were inserted to support the 
sides; the first being 12; inches diameter, and 
the lowest about 65 inches diameter, reaching to 
a depth of 1,7945 English feet. The quantity of 
water thrown up while the bore remained in this 
state was about 880,000 imperial gallons per day, 
at a temperature of 824° Fahrenheit. At a re- 
cent meeting of the Paris Academy of Sciences, a 
letter was read from M. de Humboldt, on the 
boring for an artesian well in Westphalia. It is 
intended, he says, to bore to a depth of 2,000 
metres, about a mile and a quarter English, and 
ARTESIAN WELL. 
at that depth it is supposed that the water will | 
be of the great heat of 70° centigrade. The 
borers had reached to a depth of 622 metres. To 
that depth the increase of temperature had not 
followed the ordinary law, which, according to 
M. de Humboldt, resulted from the cooling of the 
column of atmospheric air by the waters of filtra- 
tion from above; but having arrived at 622 
metres, the ascensional force was sufficiently 
great to force back the water from above, and 
the ordinary law was re-established. M. Arago 
announced that it was the intention of the French 
government to form an artesian well in the Jar- 
din des Plantes. It is intended to be 900 metres, 
that is, 200 metres deeper than the Grenelle, and 
a temperature of 31° centigrade is anticipated. 
The water will be employed to heat the hot- 
houses of the gardens, and to supply the hospi- 
tals of La Pitié and La Salpetriere. 
The principle of these wells is exactly that of | 
natural springs or fountains; and is very closely 
exemplified in the ascent of water through a fault 
or fissure or natural orifice in the strata of a 
slanting, hilly mass of rock. Water absorbed into 
the ground from the surface of a hill or superior 
piece of plain, descends till it meets an imper- 
vious stratum ; it then flows slowly through the 
portion of porous strata immediately incumbent 
on the impervious bed, following the dip or in- 
clination of that bed, and proceeding, in some | 
instances, for miles before finding an outlet; and | 
whenever it arrives at an orifice, whether natural 
or artificial, it ascends to any level not greater 
than that from which it has descended. In most 
of the terrestrial parts of the world, therefore, 
streams of water, of greater or less volume, are 
flowing beneath the surface, to well up in the 
myriads of springs which constitute the sources 
of rills and rivers; and wherever an artificial 
boring can be so made as to connect any of these 
substrata streams with a spot on the earth’s sur- | 
face not higher than the spots at which their 
waters entered, an artesian well will be formed. 
But in some cases the stream is so small, and in 
others it flows at so enormous a depth, that a | 
tolerably good geological knowledge of a district | 
is requisite for determining when an attempt to 
form an artesian well is likely to be cheap and 
successful, or when it is likely to be either very 
costly or altogether vain. At the Plymouth 
meeting of the British Association, Professor 
Sedgwick, after reviewing the general principle 
of artesian wells, noticed two districts, in the one 
of which attempts to form the wells are emi- 
nently successful, and in the other totally ineffec- 
tive. “In the eastern part of Essex, the chalk is 
covered by sandy beds of the plastic clay, and 
these by several hundred feet of impervious strata | 
of London clay, all dipping together towards the 
east. The arenaceous beds. below the London clay 
rise higher towards the chalk than the clay does, 
and absorb a considerable part of the water from 
the high grounds. By boring through the clays 
