68 THE CHIGWELL ROW MEDICINAL SPRING.
when it did not operate this way, it did by urine; and wd at
first occasion sickness and make her reach once or twice about
an hour after taking it.
I drank half a pint of it myself for several mornings. It
gave me at first a kind of uneasiness and sickness for an hour
or more, as if it wanted to pass off or come up again, but it
did not. I increas'd the dose to near a pint. This found its
way and purged me two or three times a day moderately and with-
out griping or any uneasiness. I decreas'd the dose again and
found a little more than half a pint wd keep me regular once a
day. It seem'd to give me spirits and appetite. I continue
it at times and always with the same effect.
I order'd a countryman (from some place near Collier Row)
who ask'd my opinion upon a very obstinate erysipelatous
humour in both legs to drink a full pint every morning for 3
weeks or a month; but he came to thank me at the end of the
fortnight, quite well and in great spirits.
From the manner of the operation of this water and the ex-
periments I have try'd to discover its analysis, I am of opinion
it is a compound, being a chalybeate extinction22 and a nitrious
salt blended together. Two grains of Alleppo Galls, finely
powdered, strew'd upon the surface of 16 oun8 of this water,
gave a dark purplish colour inclining to black, but soon
became turbid; but, by standing about 14 hours, it pretty nearly
recover'd its first clearness and complexion, and a reddish ocrey
sedimt precipitated to the bottom. If a few drops of oil of
vitriol be added, it will become clear as at first, without any pre-
cipitation: from hence, I conclude the dark purplish colour is
effected by alkali salts united to the acid. That the salt of
this water is rather of a nitrious kind appears plain to me from
its turbidness, and more so from its precipitation, which spt of
vitriol prevents, tho' it destroys the colour. Upon its standing
quiet for some hours, there arises a fine film or scum upon its
surface, reflecting different colour'd lights, as upon lime water;
wch is pretty comon to all chalybeate waters, and wch may
probably be occasion'd upon the seperation of the nitrious and
vitrioline parts by ye air.23 Scarbro' water discovers the same
22 "Extraction" is. perhaps, meant.
23 Mr. Dalton writes:—"By 'nitrious' must not be understood any nitric or nitrous
"compeunds, although the former might be present in small amount. From the context, the
"term 'nitrious' may be supposed to be used for the sulphate of magnesia, resembling
"nitre in some external aspects. The oxidation of the iron tannate into ochre would result