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586 PHIPPS’S JOURNAL.
the ufe of it was impracticable during any confiderable motion of the fhip. The water
obtained, likewife, poffeffed all the difadvantages common to the preceding methods.
«¢ About the fame time experiments were made with a ftill of the common conftruc-
tion, and Mr. Dove’s ingredient. ‘This method was attended with no advantage over
any that had been formerly ufed ; the diftilled was moft unpalatable; and the enormous
fize of the apparatus, which occupied a {pace of thirteen feet feven inches by fix feet one
inch, and fix feet five inches in height, rendered it impracticable on board fhips. An
experiment was immediately afterwards made with the fame ftill without any ingredient ;
the refult, however, was uniformly a moft unpalatable tafte of the water.
«* About this period, alfo, M. Poiflonnier of Paris introduced into the French
marinea ftill, three feet fix inches long, two feet wide, and eighteen inches deep. A
portion of the chimney pafled through the upper part of the {till, much in the fame
manner as that of Mr. Hoffman: thefe gentlemen fuppofed that by this means they
fhould fave fuel. The mouth of M. Poiffonnier’s ftill was thirteen inches wide, on
which he placed a tin plate, pierced like a cullender, with thirty-feven holes of fix lines
diameter each; to thefe were fixed tin pipes, of the fame bore and feven inches long,
terminating within the ftill-head. ‘The intention of this contrivance is to prevent any
of the water in the {till from pafling over into the worm, while the fhip is in confider-
able motion.
“¢ In every other refpet M. Poiffonnier employs a ftill-head, worm-pipe, and worm-
tub, with all its ufual apparatus; and he directs fix ounces of fo/fil alcali to be. mixed
with the fea water at each diftillation, to prevent the acid of the magnefia falt from
rifing with the vapour, when falt begins to form on the bottom of the {till It is pro-
bable that in M. Poiffonnier’s ftill, which was even more fhaliow in its form that Mr.
Hoffman’s, fome of the water might be thrown up toward the worm; in which cafe.
the pierced plate with pipes might be of fome fervice in breaking the direction of the
water. But by Doétor Irving’s tube this inconvenience is entirely prevented, as expe-
rience fully evinces, viz. in a voyage to Falkland’s Iflands, where it has been ufed in
diftillation every day ; in feveral voyages to the Eaft Indies; and in this voyage, as is
mentioned in the journal.
.“ M. Poiflonnier, in correéting this error in the con{tru€tion of his ftill, has intro-
duced another of the moft capital nature in diftillation. For by means of the pipe-cul-
lender, the vapour will meet with the greateft refiftance to its afcent, which will retard.
the progrefs of diftillation in a very high degree, and increafe the Empyreuma.
‘* From all the experiments above-mentioned, it is evident, that no method had
hitherto been invented of making fea water frefh, which was not attended with fuch in-
conveniencies as rendered the feveral proceffes of fcarce any utility. ‘Vhe defects ot
the various methods above enumerated, may be reduced to the following heads :
‘©, The {mall quantity of water produced by the ordinary methods of diftillation
with a ftill-head, and worm, could never be adequate to the purpofes of fhipping,
though the apparatus fhould be kept in conftant ufe ; and at the fame time, this mode
of diftillation required a quantity of fuel, which would occupy greater {pace than
might be fufficient for the ftowage of water.
“2, A ftill-burnetafte, which always accompanies this method of diftillation, and
renders the water extremely unpalatable, exciting heat and thirft, if drank when re.
cently diftilled.
«3. A total ignorance with refpeét to the proper time of ftopping the diftillation,
whereby falt was permitted to form on the bottom of the boiler ; which burning, and
corroding the copper, decompofed the felenitic and magnefia falts, caufing their acids ta
5 afcend.
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