So M O R 
gins obferves, that M, Loriot corrects the bad quality of 
the old and effete lime, which conftitutes the baiis of his 
mortar, and which has regained a part of the fixed air 
that had been expelled from it, by the addition of frefli 
and non-effervefcent lime, haftily added to it, at the time 
of ufing the compofition, which mull undoubtedly im¬ 
prove the imperfedt mafs. And he adds, that, when an 
ignorant artift makes mortar with whiting inftead of lime, 
he can mend it confiderably by adding lime to it; but his 
mortar will {till be defective. 
Dr. Higgins has made a variety of experiments, in con- 
fequence of the modern difcoveries relating to fixed air, 
for the purpofe of improving the mortar ufed in our 
buildings. According to this author, the perfection of 
lime prepared for the purpofe of making mortar, confifts 
chiefly of its being totally deprived of its fixed air. On 
examining feveral fpecimens of the lime commonly ufed 
in building, he found that it is leldom or never fuffi- 
ciently burned ; for they all effervefced, and yielded more 
or lefs fixed air, on the addition of an acid, and flaked 
flowly, in comparifon with well-burned lime. Dr. Hig¬ 
gins alfo relates fome experiments, which fliow how very 
quickly lime imbibes fixed air from the atmofphere ; on 
its expofure to which, it by degrees foon lofes thofe cha¬ 
racters which chiefly diftinguifh it from mere limeftone 
or powdered chalk; by foon attracting from thence that 
very principle, to the abfence of which it owes its ufeful 
quality as a cement, and which had before been expelled 
from it in the burning. Hence he concludes, that, as 
lime owes its excellence to the expulfion of fixed air from 
it in the burning, it fhould be ufed as foon as poflible af¬ 
ter it is made, and guarded from expofure to the air, as 
much as poflible, before it is ufed. It is no wonder, there¬ 
fore, he fays, that the London mortar is bad, if the im¬ 
perfection of it depended folely on the badnefs of the 
lime ; iince the lime employed in it is not only bad when 
it comes frefh from the kiln, becaufe it is infufficiently 
burned, and the air has accefs to it, but becomes worfe 
before it is ufed, by the diftance and mode of its con¬ 
veyance; and, when flaked, is as widely different from 
good lime as it is from powdered chalk. For a fimilar 
reafon, every other caufe, which tends to reftore to the 
lime the fixed air of which it had been deprived in the 
burning, muff deprave It. It muff receive this kind of 
injury, for inftance, from the water, fo largely ufed, firft 
in flaking the lime, and afterwards in making it into mor¬ 
tar, if that water contains fixed air, from which few wa¬ 
ters are perfectly free, and which will greedily be attracted 
by the lime. The injury arifing from this caufe is pre¬ 
vented by the fubftitution of lime-water, fo far as may 
be practicable or convenient. 
From other experiments, made with a view of afcer- 
taining the belt relative proportions of lime, fand, and 
■water, in the making of mortar, it appeared that thofe 
fpecimens were the bell which contained one part of lime 
in feven of the fand: for.thofe which contained lefs lime, 
and were too fliort whilfl frefli, were more eafily cut and 
broke, and were pervious to water; and thofe which con¬ 
tained more lime, although they were clofer in grain, 
did not harden fo foon, or to fo great a degree, even 
when they efcaped cracking by lying in the lhade to dry 
flowly. It appeared farther, that mortar, which is to be 
ufed where it muff dry quickly, ought to be made as ftiff 
as the purpofe will admit, or with the fmalleft practicable 
quantity of water; and that mortar will not crack, al¬ 
though the lime be ufed in exceflive quantity, provided 
it be made ftiffer, or to a thicker confluence than mortar 
aifually is. 
Dr. Higgins has alfo fliown, that though the fetting of 
anortar, as it is called by the workmen, chiefly depends 
on the exficcation of it, yet its induration, or its ac¬ 
quiring a ftony hardnefs, is not caufed by its drying, as 
has been fuppofed, but is principally owing to its abforp- 
tion of fixed air from the atmofphere, and is promoted in 
proportion as it acquires this principle; ttys accefliop of 
TAR. 
which is indifpenfably neceflary to the induration of cal¬ 
careous cements. In order to the greateft induration of 
■ mortar, therefore, it muff be fuffered to dry gently, and 
fet; the exficcation muff be effected by temperate air, and 
not accelerated by the heat of the fun or fire; it mult not 
be wetted foon after it fets; and afterwards it ought *to 
be protected from wet as much as poflible, until it is 
completely indurated ; the entry of acidulous gas mult be 
prevented as much as poflible, until the mortar is finally- 
placed and quielcent; and then it mult be as freely ex- 
poled to the open air as the work will admit, in order to 
fupply acidulous gas, and enable it fooner to fuftain the 
trials to which mortar is expofed in cementitious build¬ 
ings, and incrultations. Dr. Higgins has. alfo enquired 
into the nature of the belt fand or gravel for mortar, and 
into the effeCts produced by bone-allies, plafter-powder, 
charcoal, fulphur, &c. and he deduces great advantages 
from the addition of bone-alhes, in various proportions, 
according to the nature of the work for which the com¬ 
pofition is intended. 
In the xxxviith vol. of the Phil. Tranf. we have fome 
methods of making mortar at Madras in the Eall Indies, 
communicated by Ifaac Pyke, efq. at that time governor 
of St. Helena. 
i. Take fifteen bufnels of frefli pit-fand, well lifted: 
add to it fifteen bulheH of fhone-lime: let it be moift- 
ened or flacked with water in the common manner, and 
fo laid two or three days together. Then diffolve twenty 
pounds of jaggery, which is coarfe fugar, or thick rao- 
lafles, in water, and, fprinkling this liquor over the mor¬ 
tar, beat it up together till all is well mixed and in¬ 
corporated; and then let it lie by in a heap. Then boil 
a peck of gram (which is a fort of grain like a tare, 
or between that and a pea) to a jelly, and ftrain it off 
through a coarfe canvas, preferving the liquor that comes 
from it. Take aifo a peck of mvrabolans, and boil them 
likewife to a jelly, preferving that water alfo as the other; 
and, if you have a veil'd large enough, you may put thefe 
three waters together, that is, the jaggery-water, the 
gram-water, and the myrabolan. The Indians ufually 
put a fmall quantity of fine lime in it, to keep their la¬ 
bourers from drinking it. The mortar beaten up, and, 
when too dry, fprinkled with this liquor, proves extra¬ 
ordinary good for laying brick or Hone, keeping fome of 
the liquor always at hand for the workman to wet hie 
bricks with ; and, if this liquor prove too thick, dilute it 
with frelh water. Obferve alfo, that the mortar here ie 
not only to be well beaten and mixed together, but alfo 
laid very well, and every brick, or piece of brick, fluflied 
in with the mortar, and every cranny filled up, yet not 
in thick joints, like the common Englifh mortar; and 
alfo over every courfe of bricks, fome to be throwed on. 
very thin; and where the work has flood, though but for 
a breakfaft or a dining time, before you begin again, wet 
it well with this liquor with a ladle, and then lay on your 
frelh mortar; for this mortar, notwithftanding its being 
thus wetted, dries much fooner than one not ufed to it 
would conceive, efpecially in hot weather. 
a. For fome very ftrong work, the fame mortar above 
is improved as follows: Take coarfe tow, and twift it 
loofely into bands as thick as a man’s finger, (in England 
ox-hair is ufed inftead of this tow;) then cut it into 
pieces of about an inch long, and utitwift it fo as to lie 
loofe ; then ftrew it lightly over the other mortar, which 
is at the fame time to be kept turning over, fo that 
this fluff be beaten into it, keeping labourers continu¬ 
ally beating in a trough, and mixing it till it be well in¬ 
corporated with all the parts of the mortar. And, as it 
will be fubjedt to dry very fall, it mult be frequently l’of- 
tened with fome of the aforelaid liquor of jaggery, gram, 
and myrabolans, and lome frefli water; and, when it is 
fo moiftened and beaten, it will mix Vpell; and with this 
they build (though it be not ufual to build common 
houfe-walls thus) when the work is intended to be very 
ftrong, as for inftance, Madras church fteeple, which was 
4 building 
