_pleyed.—Vol. II. 
£796.) Preferving Water . 
will the cetnent be: for fome kinds of 
work, it will be better to ufe fine fand 
alone, and for others coarfe fand alone, 
remembering, that the finer the fand is, 
the greater quantity of lime is to be em- 
Pp. 289. : 
dn December; 1780 (term expired) 
R. Williams, M.D. obtained a patent 
for the invention’ of a new mortar, or 
fiucco. Lhe ingredients made ufe of, are 
the following: To 12/b. of pure lime, 
1olb. of »vater, and 84lb. of pure coarfe 
fand, add alb. of grated fkim-milk cheefe; 
let the whole be worked up together, 
and ufed as foon after as poifible ; care 
muft be taken in applying this kind of 
mortar, that the bricks, 8c. which are 
‘intended to be covered by it, be perfectly 
dry; and the greater the degree of pret- 
fure employed in laying it on, the better. 
—-Vol. LIT. p. 1. / 
1X. PRESERVINGOW ATER: 
On the fubjeé of preferving fea-water 
from putrefaction, we finda paper of 
Mr. Henry’s, of Manchefter, extracted 
from the Manehefter Philofuphical Tranf- 
actions, containing a ferics of ingenious 
experiments, of which the refult is, 
that quicklime, in the proportion of two 
feruples to one quart of fea-water, will 
effectually preferve it, for many months, 
from exhibiting any fign of putridity or 
decompofition.—Vol. I. p. 178. 
The 2d volume centains a memoir of 
M. Lowitz, read at the Gicsnomical 'So- 
ciety of Peterfourgh, on the purilication 
ef corrupted warer; from which it ap- 
pears, that one ounce and a halr of pow- 
dered charcoal, and 24 drops of vitriolic 
acid, are fuificient for the purification 
of three pints and ahalf- of corrupted 
sie ee 
Water._Veki Il. p.6r. ‘ 
N.B. Dhis ditcovery has fince been 
pretty largely carried into execution, 
and with great fuccefs ; but for this pur- 

pole, it is.meceflary to ufe fre/b-gurnt 
charcoal, or at leaft that which has 
been carefully excluded from the atmof- 
phere. 
XI. Enastic Gum. 
On this fubjeét we have a feries of ex- 
periments. made by Mr. Groffart, for 
afcertaining the beft way of making ca- 
theters, and other inftruments, of elaftic 
gum ; the refult of which is, that the 
moft practicable method is to cut a bot- 
tle of the gum into one {piral flip, and 
having macerated it for fome time in 
ether and water, tillit becomes fticky, 
to rollit carefully round the mould, and 
fhen cover it with a bandage of cord; 
‘Ana few days a complete union of the 
i 
~- Gum... Salt-Petre. : 209 
fides of the gum will be effeéted, the 
bandage may be taken off, and the 
mould withdrawn by the affiftance of 
hot water. Mr. G.has alfo met with 
equal fuccefs, when the gum was laid in 
boiling water for a quarter of an hour, 
without making ufe of ether.—Vol. I. 
Jerson 
A patent was granted, in January, 
1781 (term expired) to Mr. Albert 
Angell, of Bethnal-Green, Middlefex, 
fora compofition, called Britannic Elaf— 
tic Gum, of which the follawing are the 
ingredients: Linfeed, or nut oil, one 
gallon; bees-wax, ilb.; glue or fize, 
61b.; verdigrife, a quarter of a pound ; 
litharge, a quarter of a pound; rain 
water, two quarts; the whole to be 
melted down in an iron kettle till it be- 
comes of the proper confiftence.—Vol. 
PA pasa 
MIE. SALT-PETRE. 
The third volume contains a valuable 
effay on this fubje€i, by James Maffey, 
Kifq. (extracted from the Manchefter Phi- 
lofophical Tranfaétions) the leading ideas 
of which are the following: Salt-petre 
is formed by an union of the nitric acid 
with vegetable alcali; the alcali exifts in 
wood afhes ; the acid in thofe fubftances 
that have undergone the whole putre- 
faciive fermentation, fuch as the earths 
of ftables and cow-ftalls, and the foil at 
the bottom of graves; the common pea- 
fants of France and Germany, who are. 
almoft all falt-petre makers, {crape toge- 
ther the offals of their farm-yards, and 
throwing them under open fheds, drench 
them occafionally with urine and muck 
water, till they find them capable of an- 
{wering their purpofe. Thefe mate- 
rials, with the wood athes which their 
hearths fupply, are thrown intoa large 
tub, and water poured upon them, which 
runs out ata hole fiuffed with ftraw at the 
bottctn of the veffel; the leys being 
thus procured, are boiled down and fer 
by to cryftallize. The falt-petre mak- 
ers at Paris, cniefly make ufe of the rub- 
bifh of old houtes, &c. which having 
reduced to a coarfe powder, and fitted, 
they preceed as follows : they prcvide a 
number of {mall open tubs, which are 
placed on ftillages infuch a manner, that 
one vefiel may receiye the ley that runs 
from two of them. Tn each tubnear the 
bottom, is placed a {piggot and faufet; 
and, to prevent its being choaked by the 
wood afhes, a parcel of the round earth 
is thrown in firft, and the/afhes upon it’: 
they then add the remainder of the earth 
in the proportion of two buthels : the 
atter, 
