66 THE CHIGWELL ROW MEDICINAL SPRINGS.
then left off [digging] and, in one night's time, I suppose there
might be 6 or 8 Hhds. of water in the well. It had a steely and,
at the same time, a saline tast; a thick scum on the top, re-
flecting various colours; and its smell [was] volatile and
sulphureous.18
The Reader may now, perhaps, expect the natural history
of waters, their origin, the cause of springs, the nature of all
mineral waters, with their analysis, specific gravities, etc.,
etc.; but, as these matters would lead me far beyond the bounds
of a pamphlet, I hope I shall be excused from entering upon a
work that would fill a folio. However, the subject naturally
leads me to say something of water in general, which will give
some information to the reader and which he may compare and
contrast wth such as are render'd medicinal—i.e., by being
mixed wth metalline and fossil substances. . . .
[The writer then discourses at length on various kinds of
waters—Rain water, Spring water, River water, Pump water,
Pond or Stagnant water, and so on. He next proceeds to set
forth (with what was certainly, for those days, considerable
chemical knowledge) the various tests by means of which the
purity of waters and their mineral or saline constituents are
ascertained. He concludes:—]
Chigwell row water, by the addition of [Aleppo] galls, turns
black; with urinous salt, greenish; with lime water, turbid
and bluish; [and], with Sal Saturni, milky. This water, by
being exposed in an open bottle, drops its ocrey sediment and
with it a great deal of its power of tinging with galls. In about
12 hours time, by exhaling of three 4ths. away, the remaining
part shot into a figured salt, which tasted bitterish and astringent,
"mass, but often segregated into nodules or impregnating fossil wood. The 'particles'
"are most probably crystals of selenite (sulphate of lime), formed by the oxidation of the
"pyrites into sulphate of iron and by the action of this on carbonate of lime, either native
"to the clay or derived by the infiltration from the overlying Boulder Clay. Lower down,
"the diggers found the soil becoming 'more yellowish and okery.' They had corne upon
"one of the sandy bands in the upper portion of the London Clay (indicating the
"approaching change into the Bagshot Sands), and this brought in from its outcrop a feeble
"supply of water, the oxygen dissolved in which first helps to form the sulphate of iron,
"as mentioned, and then to break up some of it or of the carbonate into ochreous peroxide,
"leaving the rest in solution, with other salts unaltered.'
18 Mr. Dalton writes:—"The term volatile, as applied to smell, may imply pungency, but
"more probably means evanescent, the smell disappearing on the escape of the sulphuretted
"hydrogen, which is generally present in such chalybeate waters. The taste would be due
"predominantly to carbonate of iron, partly to the sulphate, and partly to the Epsom salts
"(sulphate of magnesian, which is largely present in many Essex waters. Some sulphate of
"alumina may also occur. The iridescent colours are due to the formation of a film of
"insoluble peroxide of iron in contact with the air."