27 
SEA- WATER. 
“ Behold the sea, 
The opaline, the plentiful and strong, 
Yet beautiful as is the rose in June, 
Fresh as the trickling rainbow of July ; 
Sea full of food, the nourisher of kinds, 
Purger of earth, and medicine of men ; 
Creating a sweet climate by my breath, 
Washing out harms and griefs from- memory, 
And, in my mathematic ebb and flow, 
Giving a hint of that which changes not ''—Emerson. 
jpSfejlHO that has ever taken a dip in the sea is not aware 
iVVfVjSI that its wa * er is distinctly salt in taste and more 
buoyant than fresh water ? These two characteristics 
are intimately connected. Let us examine them a 
little more closely. If we fill a good-sized bottle first with pure 
water and afterwards with sea-water and weigh it carefully on 
each occasion, we shall find that it is heavier when filled with 
salt water. Quantitatively accurate experiments will inform us 
that if a given measure of pure water weigh 1,000 lbs. the same 
measure of sea-water will weigh from 1,024 to r >° 2 7 lbs., accord- 
ing to the nearness of large rivers, melting ice or hot winds. 
River water, it is true, is by no means pure. Thames water, in 
fact, contains about 21 grains of saline matter per gallon; but 
this is not perceptible to the taste, and sea-water contains more 
than a hundred times as much, from 3! to 4 per cent., that is, 
of its entire weight. In consequence of this greater density of 
sea-water, not only is it easier for us to float or swim in the sea 
than in a river, but heavy rain falling on a calm sea, or the water 
carried down by a swift river, will float for a time on the 
surface and may even be bailed off it. 
If we compare the taste of sea-water to that of ordinary salt 
and water, we shall detect that the former is not only salt but 
bitter, and we may also notice a certain flatness or alkalinity, 
reminding us of the taste of carbonate of soda in water. A 
little sea-water boiled down till a considerable proportion has 
passed off as steam will taste decidedly more salt and more 
bitter ; and a very pretty, though simple, experiment is to take 
a drop or two of this concentrated sea- water, having first stirred 
it well so as to mix its constituents completely, and finish its 
evaporation under the microscope. In a warm room the water 
will soon evaporate; but the salts it contains will not do so. 
As we watch the vanishing water, numbers of beautiful sym- 
metrical crystals will be seen to shoot into being. The first to 
appear will be oblong, pointed at one end, and barbed like an 
arrow at the other. These are precise miniatures of those 
limpidly transparent arrowheads of selenite that occur near the 
surface of the clay of Oxford or of Sheppey. They are gypsum 
or hydrous calcium-sulphate, and, though by no means the 
most abundant of the salts present in the water, they appear 
