SHEA-WATER. 
and never fails to vindicate the expectations of 
its effects.” 
SEA-WATER. The water of the ocean and 
of its inlets, A specimen of it analysed by Mar- 
cet contained 2°666 ‘per cent. of chloride of so- 
dium, 0°466 of sulphate of soda, 0°1232 of chloride 
of potassium, 0°5152 of chloride of magnesium, 
and 0:0153 of sulphate of lime; and a specimen 
from the North Sea, analysed by M‘Clemm, con- 
tained 2°484 per cent. of chloride of sodium, 
| 0135 of chloride of potassium, 0°242 of chloride 
of magnesium, 0°12 of sulphate of lime, and 0:206 
of sulphate of magnesia. Sea-water, as a compari- 
son of these two analyses may suggest, varies some- 
what widely in constituency in different latitudes 
and in different seas ; it also varies, in any one sea 
near the coast, in rainy and in dry seasons, or 
within or without the sweep of fresh-water cur- 
| rents from rivers; and, in addition to its main 
saline constituents mentioned in the two analyses 
which we have quoted, it usually contains very 
minute or inappreciable quantities of ammonia, 
| carbonic acid, silica, magnesia, iron, manganese, 
_ sulphuretted hydrogen, organic matter, carbonate 
_ of lime, phosphate of lime, and iodides and bro- 
mides. It has a specific gravity of from 1:0269 to 
1-0285; and is heavier in the higher latitudes of the 
torrid zone than at the equator. It owes its saline 
taste to its chlorides and sulphates,—and chiefly 
to its chloride of sodium ; and it owes its nause- 
ousness to the combination of these with its 
small quantity of organic matter. 
The continual evaporation of the ocean, aided 
by the action of winds, sends a supply of the 
salts of sea-water over the whole surface of the 
world, and constantly contributes them, through | 
the medium of rain, for the enriching of soils, 
and for the nutrition of all salt-loving plants. 
The air hanging over any part of the sea always 
contains enough of common salt to make a solu- 
tion of nitrate of silver turbid; and the leaves 
of plants growing to windward of sea-storms, 
even at the distance of from 20 to 30 miles from 
the shore, are sometimes covered with crystals 
of salt. Mere ordinary evaporation from the 
ocean, therefore, and especially a prevalence of 
sea-breeze in any stated direction, must be al- 
ways an appreciable and sometimes a highly valu- 
able source of the chlorides of sodium, potassium, 
and magnesium, and the sulphates of lime and 
soda and magnesia to the plants of the garden 
and the farm. Though the carbonate of lime in 
sea-water amounts to less than a twelve-thou- 
sandth part of the water’s weight, it affords the 
incalculable myriads of corals and marine mol- 
luscs a sufficient supply for the construction of 
their habitations; and though the iodine in sea- 
water amounts to less than one-millionth of the 
water’s weight, it is everywhere readily enough 
collected, absorbed, and assimilated by the Fu- 
coidex which require it as an aliment; so that if 
the quantity of salts evaporated from the ocean, 
and distributed by wind and rain throughout 
SECRETION. 
165 
the world, were vastly less than it is, it could 
not fail to exert an appreciable and constant in- 
fluence on vegetation. The comparative saline 
wealth or poverty of any piece of land, therefore, 
must materially depend on its distance from the 
ocean, or on the degree in which it is swept and 
watered by breezes and exhalations and rains 
from the sea. 
Sea-water is sometimes used for saturating 
dung -heaps and fold- yards, at short intervals 
during dry weather, in places upon the coast 
where it can be obtained and applied at a trifling 
expense of labour. But the main or only useful 
purpose which it can serve in this way is to im- 
pregnate the heaps with its saline principles; 
and either this purpose may be quite unneces- 
sary on account of the heaps themselves or the 
soil to which they are to be applied already con- 
taining a sufficient quantity of these principles, 
or it may be more facilely and cheaply accom- 
plished by means of a sprinkling of bathing salt. 
A farmer should consider, also, whether his dung- 
heaps may not get more injury from the exces- 
sive moisture of the saturations than they can | 
get good from the impregnations of saline prin- | 
ciples. See the article Sanur (Common). 
SHA-WRACK. See Sza-Warz and Fuct. 
SEA-WRACKGRASS. See Wrackerass. 
SEBAIA. A genus of ornamental, exotic, an- 
nual plants, of the gentian family. Five species, 
all late-bloomers and only a few inches in height, 
have been introduced to Britain, from Australia 
and Southern and Western Africa; and they 
require greenhouse treatment, and have severally 
white, yellow, brown, and red flowers. 
SEBESTEN PLUMS. See Corpta. 
SECALE. See Rye. 
SHCAMONE. A genus of exotic, evergreen, 
twining plants, of the swallow-wort tribe. The 
emetic species, S. emetica, possesses medicinal 
properties. It has a height of 6 or 7 feet, and 
carries white flowers, and was introduced to 
British collections about 32 years ago from India. 
SECHIUM. See Cuoxo. 
SECRETION. The function by which a living 
organ selects and separates certain principles 
from the fluids which pass through it or upon 
it; also, the amassment of the principles which 
this function selects and separates, or the sub- 
stance into which they are transmuted in their 
separated state. Secretion, in the former sense, 
either assimilates or expels,—either appropriates 
the separated principles as part of the living body 
to which the organ belongs, or drives them into 
a course of being rejected from it on account of 
their unfitness for its nutrition; and a secretion, 
in the sense of the principles themselves, is a 
proper or recremental secretion when destined 
to assimilation, and an excremental secretion or 
an excrement when destined to expulsion. The 
secreting organs, in both animals and plants, 
are principally glands, cells, membranes, and in- 
finitesimal tubes. 
