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^ e pared by the common workman, without machinery, andJcost not much exceeding that of common lime.

.description given by M. Vi cat of the mode in which<irj, art *ficial hydraulic limes are prepared is as follows:—the ' e arl; *dci a l hydraulic limes are prepared by two methods:

, m ° st perfect, but also the most expensive, consists inti 0n * n o with rich lime slacked in any way, a certain propor-tion 1 ^ and calcining the mixture; this is termed arti-uai hme twice kilned.”

Ve the second process, we substitute for the lime any- lV i. calcareous substance (such, for instance, as chalk),In tl • ' s ea sy to bruise and reduce to a paste with water.j 3 118 "'ay a great saving is effected, but at the same timee< lual° CUre ^ an artificial lime of good quality, though notof to that derived from the first process, in consequence<i ® ra ther less perfect amalgamation of the mixture.”

\v e e se e that by being able to regulate the proportions,e nep ^ an also give to the factitious lime whatever degree ofthe We Pl ea se, and cause it at pleasure to equal or surpass

«i( r tur;| l hydraulic limes.”

'* e

of v e dually take twenty parts of dry clay to eighty partsof r ‘ c h lime, or to one hundred and forty of carbonateor e (, This refers to the lime in the unslacked condition,

Proi

the

'Portio

uncalcined mineral. If the lime be slacked, the

or 4011 should be increased to 110 parts. But if the limethe n ^’kuuate should already be at all mixed with clay in■hloreov Ura ^ - State ’ then fifteen parts of clay will be sufficient.eVer y 1 13 P ro P er to determine the proportions for

a note^it . m * xtu ro here described,” adds Captain Smith in

5 is SllP.V) oa tho lurrlroiilin limoa tirlinoo

. 18 such as to produce the hydraulic limes, whoses howg ! es are similar to the Aberthaw, the analysis of whichto correspond nearly with the proportions herell,2 cla -<lcd, as it consists of 86.2 of carbonate of lime toat tj le a ^’ (with 2.6 water and carbonaceous matter), being"Plie Ce ; lte °f 18.2 parts clay, to 140 of the carbonate of lime.Se ttino. t , ents now m use m England, are much quickertain a , r latl these, and differ in being unslacked. They con-ar tifician eatei ! P ro portion of clay, but may be manufactured? Uai >tit;‘ y ' Vit , h „ ec i ual ease, by combining such relativei n tend e j S c halk, or lime, and clay, as will suit the purposeButnph ' Tarker's Patent Cement, as analyzed by Sirlinj e e y Davy, contains 45 per cent of clay to 55 carbonatei e > tl t le ^°rkshire cement, 34 clay to 62 carbonate of4 Ifii-yi/ .^hoppej', 32 clay to 66 carbonate of lime; and*9 cart, 10 w hich is a quicker-setting cement, 47 clay toseems to be evident from the°I' hi- Vicat, that the manufacture of artificiala . diff er a .f he almost infinitely varied by the admixturel0r >s 0 p , ln gredients. The character, quality, and propor-^P er itnent R f e must ' Je l' 16 result of actual practice and. a Ppar en j/ or , so different may be the chemical propertiesj Cc es s p u j . y similar materials, that no results, howeverpi a . n °the r . ln t' 16 localit y» can be trusted to with certaintyj- ieu] ai , ' ^ .1® only necessary to add, that in all cases,

' 0ri of * en tion should be paid to the perfect amalgama-t] to u ^^rials; and the degree of calcination bestlp ^anuf., s “°uld be carefully observed, before attemptingat A e Pro" Ure on a l ar g e scale.

t : hleudon SS made use of at a manufactory of artificial limecp^'iiils r ’ I \ ear Paris , is thus described by M. Vicat—“ Theof y, U| a . use °fi are the chalk of the country, and thea 8 f l ® size 0 f gard ’, w klch is previously broken up into lumpss «t r ? n § wl ? ne . s fist- A millstone set up edgeways, and6ip°- l ‘arr 0 ! w I f fi spokes and felloes, firmly attached to a’ lr > a ci re ^ and rakes, are set in motion by a two-horseU ar basin of about two metres (six feet and a

half English ) radius. In the middle of the basin is a pillarof masonry, on which turns the vertical arbor to which thewhole system is fixed: into this basin, to which water isconveyed by means of a cock, they throw successively fourmeasures of chalk, and one measure of clay. After an hourand a half working, they obtain about 1.50 metros cube(nearly 53 cubic feet English ), of a thin pulp, which theydraw off by means of a conduit pierced horizontally on a levelwith the bottom of the basin. The fluid descends by its ownweight; first into one excavation, then into a second, thena third, and so on to a fourth or fifth. These excavationscommunicate with one another at top; when the first is full,the fresh liquid, as it arrives, as well as the supernatantfluid, flow over into the second excavation ; from the secondinto the third, and so on to the last, the clear water fromwhich drains off into a cesspool. Other excavations, cut insteps like the preceding, serve to receive the fresh productsof the work, whilst the material in the first series acquiresthe consistency necessary for moulding. The smaller thedepth of the pans in relation to their superficies, the sooneris the above-mentioned consistency obtained.

“ The mass is now subdivided into solids of a regular form,by means of a mould. This operation is executed withrapidity. A moulder, working by the piece, makes on anaverage five thousand prisms a day, which will measure aboutsix cubic metres (211.8 cubic feet English ). These prismsare arranged on drying shelves, where in a short time theyacquire the degree of desiccation and hardness proper forcalcination.”

These artificial limes are intended to supply the place ofthe natural ones in those countries where argillaceous lime-stone cannot be obtained. The price at which they weresold in Paris a few years back, was about £2. 5s. per cubicyard English .

Maltha , and mastic, are cements, whose hardness dependson the oily or mucilaginous substances that enter into theircomposition. The use of these is at present very limited inEurope ; but they were highly esteemed by the ancients,especially for stucco. The maltha of the Greeks seems tohave been more simple than that employed by the Homanarchitects ; at least we are informed, that Panmmas, thebrother of Phidias , lined the inside of the temple of Minerva,at Elis, with stucco, in which the usual ingredients of sandand lime were mixed up with milk, instead of water, somesaffron being added, to give it a yellow tinge. The Romanmaltha, according to Pliny , was prepared as follows: Takefresh-burnt lime, and slack it with wine, then beat it up verywell in a mortar, with hogs’ lard and figs: this cement, ifwell made, is excessively tenacious, and in a short timebecomes harder than stone; the surface to which it is to beapplied is to be previously oiled, in order to make it adhere.Another kind almost equally strong, and considerably cheaper,was prepared by beating up together fine slacked lime, pul-verized iron scales, and bullocks’ blood.

In the preparation of maltha, as well as of every other kindof mortar, so much depends on the manipulation, and on thecare and long beating of the ingredients, that those countriesin which labour is of the least value, possess, in general, thebest mortar. Hence, no doubt, principally arises the unrivaledexcellence of the mortar made by the Tunisians, and otherinhabitants of the northern coast of Africa . Dr. Shaw givesthe following account of their manner of preparing theirmortar: One measure of sand, two of wood-ashes, and threeof lime, being previously sifted, are mixed together, andsprinkled with a little water ; after the mass has been beatensome time, a little oil is added : the beating is carried on forthree or four days successively, and, as the evaporation in