MOE

217

MOE

G t ’ kite lime, and the whitest bone-ash, are to be chosen,tte f n S ^ n< k and gray bone-ash formed of half-burnt bones,of (], e chosen to make cement gray ; and any other colouror fc^ent is obtained, either by choosing coloured sand,tal c in ” 10 ^mixture of the necessary quantity of colouredor P° w <ler; or of coloured, vitreous, or metallic powders,paia ti W durable colouring ingredients, commonly used mXi' -

Cable'' 8 c ® men t> whether the coarse or fine-grained, is nppli-of t b ' n for ming artificial stone, by making alternate layersthe fi Cement and of flint, hard stone, or bricks, in moulds ot80 f 0r ^ °f the intended stone, and by exposing the masses■\yi e< f t0 the open air, to harden. .

of tj, 11 su ch cement is required for water-fences, two-tlnrdsand ; prescribed quantity of bone-ashes are to be omitted ,ter r ’ a fke place thereof, an equal measure of powderedCo ar ’, s to b e used ; and, if the sand employed be not of thesh a q h Sor k more terras must be added, so that the terras'\y. e °ne-8ixth part of the weight of the sand.

* fluid- such “

" for — a cement ' s required of the finest grain, or inPoivde^ o m ’ f° tbat If may be applied with a brush ; flintS * ! '0C(> ^ r foe powder of any quartzy or hard earthy sub-8* lalle <'> m be U8ed in the place of sand ; but in a quantity^ H'at'th P^°P° r tion as the flint or other powder is finer ;p e than . lnt ~P°vvd er , or other such powder, shall not he!■»« i( a s | x times the weight of the lime, nor less than fourQ lase limit 6 i greater the quantity of lime within

A'flck drv; S> more will the cement he liable to crack byWhere anc * T ' ce -versa.

P r °cured 6 above described sand cannot be convenientlySorte'd r ,, w kere the sand cannot be conveniently washedn 0!ll ' Se and fi * at S!m< l which most resembles the mixture ofa, r ,°. v 'ded d " e Sand above prescribed, may be used as directed,*'ch ; g , ue attention be paid to the quantity of the lime,

I Wl lp „ c ° be srre.nto,. ,1- 1:»-c---J .-■>

h °dv. ! e S! >nd

Wl lere -“ °c greater as the quality is finer, and vice vers;!,or b a] cann °t be easily procured, any durable stonyw ll*e sizpi? U , d eai ‘th, grossly powdered, and sorted nearly

—o v~ «™i, grossly powdered, and sorted nearly'v'\ Ce of 8 above prescribed for sand, may be used in theunu’ me ? 8ure fm- measure, but not weight for" * a n<l, 88 su cli gross powder be specifically as heavy

5' 1( be c ' eanse< l from every softer, lighter, and less

to

>0,

1 h

and from that part of the sand which is toovvp 10U8 methods, preferable in certain circumstancesW a t..„ llcb ''as been already described.

^euita Kla y ke found naturally free from fixable gas,

‘Aem.’- 0 ! - cl, ‘" ■ - ’

W -Uce, b g " <i y ’ sucb water may, witliout any great incon-of s ufg(.' Used m tfie place of the lime-water ; or a lime-, lentl y useful, may be made by various methods-yjjy So? tQe au< f water in the described proportions, or

tvl l ; C | an ^'k’me cannot be procured, chalk lime, or shell6 Xc!> ac k irs of r res embles stone - lime in the foregoing

lm Ce t>ti,

J>6 ,. l ' a Ug u' lnie > may be used in the manner described,I'l^tjuireq mirteen pounds and a half of chalk-lime will' v itl l Pr °Portj 0n be .Pl a ce of fourteen pounds of stone-lime.

’'‘cotiv ° • *'me, as prescribed above, may be increasedc<J1 itr. "'li er( , e . nit i nce > when the cement or stucco is to beAtf,. ai X case h -' S not ba fiW t0 dry quickly ; and, in theptice lime ' US P 10 P 0rt *°n may be diminished. The

'‘Ue sun’i' 11 T Uant ity or quality, may be very advan-

n;'' Vu ter t, p md, by - ‘

CV t-° Soak

‘‘e i: “t inf„ — *“io me iSfuf^ater'’? 18 .^- tirae ;

causing a considerable quantity ofinto the work, in successive portions, andso that the calcareous matter of

and the matter attracted from the open air,

Po 'vder I then the work -

T °* almost every well-dried or burnt animal3 K

substance, may be used instead of bone-ash ; and severalearthy powders, especially the micaceous and the metallic ;and the elixated ashes of divers vegetables whose earth willnot burn to lime, as well of the ashes of mineral fuel, whichare of the calcareous kind, but will not burn to lime, willanswer the ends of bone-ash in some degree.

The quantity of bone-ash described, may be lessened with-out injuring the cement; in those circumstances especially,which admit the quantity of lime to be lessened, and in those 1wherein the cement is not liable to dry quickly. The art of ■remedying the defects of lime, may be advantageously prac-tised to supply the deficiency of bone-ash,' especially inbuilding, and in making artificial stone with tiiis cement.

As the preceding method of making mortar differs, in manyparticulars, from the common process, it may be useful toinquire into the causes on which this difference is founded.

When the sand contains much clay, the workmen find thatthe best mortar they can make must contain about one-halflime ; and hence they lay it down as certain, that the best ;mortar is made by the composition of half sand and halflime.

But with sand requiring so great a proportion of lime asthis, it will be impossible to make good cement ; for it isuniversally allowed, that the hardness of mortar depends onthe crystallization of the lime round the other materials whichare mixed with it; and thus uniting the whole mass into one ’solid substance. But if a portion of the materials used beclay, or any other friable substance, it must be evident that,as these friable substances are not changed in one single par-ticular by the process of being mixed up with lime and water, jthe mortar, of which they form a proportion, will consequently |be more or less of a friable nature, in proportion to the quan- jtity'of friable substances used in the composition of the mor- jtar. On the other hand, if mortar be composed of lime and jgood sand only, as the sand is a stony substance, and not in ;the least friable, and as the lime, by perfect crystallization,becomes likewise of a stony nature, it must follow that a massof mortar, composed of these two stony substances, will itselfbe a hard, solid, unfriable substance. This may account forone of the essential variations in the preceding method fromthat in common use, and point out the necessity of neverusing, in the place of sand, which is a durable stony body,the scrapings of roads, old mortar, and other rubbish, fromancient buildings, which are frequently made use of; as all ofthem consist more or less of muddy, soft, and minutely divi-ded particles.

Another essential point is the nature mid quality of thelime. Now, experience proves that, when lime has been longkept in heaps, or untight casks, it is reduced to the state of ,chalk, and becomes everyday less capable of being made intogood mortar; because, as the goodness and durability of the jmortar depends on the crystallization of the lime, and, as expe-riments have proved, that lime, when reduced to this chalk-like state, is always incapable of perfect crystallization, itmust follow, that, as lime in this state never becomes crystal-lized, the mortar, of which it forms the most indispensablepart, will necessarily be very imperfect; that is to say, it willnever become a solid stony substance ; a circumstance abso-lutely required in the formation of good durable mortar.These are the two principal ingredients in the formation ofmortar ; but, as water is also necessary, it may he useful topoint out that which is the fittest for this purpose ; the bestis rain-water, river-water the second, land-water the next,and spring-water last.

The ruins of the ancient Roman buildings are found tocohere so strongly, as to have caused an opinion, that theirconstructors were acquainted with some kind of mortar, which,