SEA SAND. 
45 
The drying may be more completely effected in an open 
evaporating basin, the sand being stirred with a test-tube of 
cold water until it no longer adheres to the outside of this 
tube. A sample of such dried sand was first cooled in dry air, 
then weighed, and left exposed to the atmosphere; it gained 
weight. It is reasonable to suppose that some sea salt was 
on the surface of the grains of sea sand, and that just as the 
properties of sea weed (changing wet or dry with the weather) 
appear to depend upon the sea salt on its surface, so perhaps 
the sea sand may change its weight with the moisture of the 
air. But this we have not proved. 
The familiar spade and bucket experiment of moulding sand 
into sand pies depends for its success on the grains being 
slightly damp. Really dry sand is quite loose, and foundry 
sand is purposely made damp for moulding. 
The suspicion that salt exists on the surface of sand can 
easily be verified. We have only to compare the result of 
running some distilled water through a clean filter paper and 
some more water through unwashed sea sand. The milky 
cloud in the presence of silver nitrate reveals the difference 
usually attributed to sodium chloride. But here let us beware 
lest because the school books call common salt sodium chloride 
we should rashly conclude that it is the sodium chloride on 
the salt grains which keeps them moist. There are many 
A. 
salts in sea water, and the damp detaining properties may be 
chiefly due to magnesium or calcium compounds, either alone 
or in conjunction with sodium chloride. It is, I believe, this 
damp detaining power which, in conjunction with its round¬ 
ness, disqualifies sea sand for making mortar. 
So far then we find that sea sand contains water and salts 
as well as sand. Now for the sand.— 
We have worked with sand washed free from salt and then 
dried. A curious change of tint occurs in the drying if the 
temperature gets needlessly high, the yellow tinge changing 
to pink, but of this more presently. 
We h ave inquired into the size of sand grains. These are 
most conveniently measured by strewing them on a micro¬ 
meter—a sheet of glass ruled with lines of an inch apart 
-—which may then be observed through the microscope. The 
