A HISTORY OF SALT-MAKING IN ESSEX. 203
a brass skimmer. Soon after the water has boiled, salt-crystals
begin to form on the surface, in a manner which is most interest-
ing to watch. These crystals (Pl. xxxii) are extremely curious
objects—thin, white, shell-like, quadrangular at base, rising in
the shape of a pyramid with a truncated cone.29 In size, they
vary greatly—some being as much as two inches square: others,
equally perfect, no more than one-eighth of an inch. The form
is invariable, but the size seems to be determined at the com-
mencement of crystallization; and, after a crystal has started to
form, it does not grow. The gentler and shorter the boiling, the
finer and more perfect the crystals: violent boiling breaks them
into fragments. Such crystals as these are often called "hopper-
crystals" (in French, tremis). Maxwell Lyte says30 that they
tend to form only in still brine. It is said,31 too, that the addition
of a small quantity of alum to the brine tends to increase
their size, but this is not done, I believe, at Maldon.
Finally, those crystals which have formed on the surface
are skimmed off and set aside for use as the finest
table-salt; those lower down are next taken out and used as
pickling-salt; while the residue then left in the pan, being less
pure, serves for agricultural purposes. This operation
is repeated daily, two pans being boiled, the daily yield of salt
being about half a ton, or about eighty tons annually.
This output is, of course, insignificant in quantity when
compared with that of the Cheshire and Worcestershire rock-
salt industry, amounting to hundreds of thousands of tons
annually; but, in respect of purity and attractive appearance,
Maldon Crystal Salt is far superior to any other produced in
Britain, and this enables it to hold its own on the market.
Practically, indeed, it reaches the standard of absolute chemical
purity, consisting of common salt (chloride of sodium) with an
admixture of no more than 0.383 per cent. of other matter, as
the following analysis by Dr. A. H. Hassall shows:—
Maldon Crystal Salt Company's Pun Table Salt.
(100 parts by weight)
Chloride of Sodium............................. 99.617
Chloride of Magnesium.......................... 0.198
Sulphate of Magnesium.......................... 0.067
Sulphate of Lime .............................. 0.118
Total 100.000
29 A salt-crystal forms the trade-mark of the company. 
30 Spoil's Cyclopaedia, ii, p. 1710 (1882).
31 Thorpe's Dic. of Applied Chemistry, iii, p. 436.