and had confequently retained a part of its original or native fixed air. Mortar muft likewife fuffer injury from the fame caufe, though not perhaps in an equal degree; as not expofing fo much furface to the air as the dry and fpungy lumps of quicklime though it is a prevailing opinion among the workmen, who generally make a large quantity at once, that it is not the worfe, but rather the better, for being kept fome time.. The Author takes notice of a particular cafe or two, in plaiftering and ftucco work, in which this obfervation of theirs holds good, and which has given origin to this error.

From a confideration of the circumftance above mentioned, Dr. Higgins very properly deduces a principal caufe of the imperfection of our common cements; even when the lime has been fufficiently burned. Being expofed,' fays he, a confiderable time before it is made into mortar, and drinking in acidulous gas all the while, the quicker as it is the better burned, it is incapable of acting like good lime, when it is made into mortar; and often approaches to the condition of whiting, which with fand and water makes a friable perifhable mafs, however carefully it be dried. In London particularly, they ufe lime which is burned, at the diftance of ten or twenty miles or more, in Kent and elfewhere, with an infufficient quantity of fuel. This lime remains in the kiln, to which the air has accefs, for many hours after it is burned. It is expofed for fome days in the transportation, and on the limewharfs; and it undergoes further exposure and carriage before the artift flakes it for mortar. It is no wonder that the London mortar is bad, if the imperfection of it depended folely on the badnefs of the lime; fince the lime employed in it is not only bad when it comes fresh from the kiln, but becomes worse before it is ufed, 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 restore to the lime the fixed air of which it had been deprived in the burning, muft deprave it. It must receive this kind of injury, for inftance, from the water, fo largely ufed, firft in flaking the lime, and afterwards in making it into mortar; if that water contains fixed air, from which few waters are perfectly free; and which will greedily be attracted by the lime. The injury arifing from this caufe is prevented by the fubftitution of limewater, fo far as may be practicable or convenient.

The Author next recites various experiments made to ascertain the best relative proportions of lime, fand, and water, in the making of mortar; and afterwards authenticates the beft proportions thus indicated in his trials, by an actual analysis of fome of the oldeft and hardest cements, which he examined for this purpofe.

His fubfequent experiments fhew, that though the setting of mortar (as it is called by the workmen) chiefly depends on the exficcation of it; yet its induration, or its acquiring a ftoney hardness, is not caufed by its drying, as has been fuppofed; but is principally owing to its abforption of fixed air from the atmofphere, and is promoted in proportion as it acquires this principle; the acceffion of which is indifpenfably neceflary to the induration of calcareous cements.

In the fubfequent fections, the Author treats of the fand or gravel ufed in mortar, and of the effects produced by bone-afhes, plaifter powder, charcoal, fulphur, and various other fubftances, occafionally introduced into it for different purposes. His obfervations and trials on this head are numerous; but will not admit of abridgment. We fhall only obferve, that he draws very great advantages from the addition of bone-afhes, in various proportions, according to the different nature of the work for which the compofition is intended.

It is

An opinion has long been entertained, that the ancients úfed fomething which is unknown to us in their mortar; and that this long loft ingredient is the caufe of the hardness and duration of thofe cements, which we fo much admire in some of their buildings. The Author however controverts the fuppofed fkill of the ancients on this head; and alleges that we have the most fatisfactory reafons to conclude that it did not exceed that of our modern builders, in the preparation of lime or mortar. certainly very improbable, as he obferves, that the remembrance of an useful ingredient, or any knowledge once acquired in an art practifed in fo many countries, fhould have been loft. The excellent fpecimens of their cement, that remain in aqueducts and other ftructures, he confiders rather as monuments of the good luck, than of the skill, of the builders. From the perufal of the following enumeration of the circumftances which might fortuitoufly concur, fo as to render fome of their cements uncommonly hard and durable; our Readers will collect fome of the circumstances requifite to the formation of good and lafting mortar, which we have not yet noticed.

When,' fays he, the neighbouring quarries afforded good lime-ftone, free from gyffum, and fuch as required to be well burned, before it could flake freely; when the preparation of the lime, at the public expence, afforded no temptation for parfimony in fuel; and when the vicinity of the lime-ftone, and the quick confumption of the lime in great maffive works, prevented those injuries which it fuftains in long transportation and expofure, in the flaking of great quantities of it at once, or in the keeping of mortar made with it, the ignorance of the artifts could not produce any defects dependent on bad lime;

6

because

becaufe neceffity or chance inforced all that could have been fought by choice, in this inftance.

When the vicinity afforded fand, clean, quartofe, fharp, well fized, and refembling our mixture of the coarse and fine; chance furnished all that skill could aim at, in the choice and preparation of this article.

When walls of immenfe thicknefs were conftructed chiefly with fmall ftones, in the way of boulder-work, the great confumption of mortar made every practicable faving of lime an object of great importance; and as the mortar must be made ftiff for fuch work, it was neither convenient nor neceffary to mix much lime in it, or to ufe fine fand in it, or to exclude the rubble from it and thus, by motives of economy and convenience, rather than by any others, they were led to the measures which infured, to the cement of fuch ftructures, every perfection dependent on the goodness of lime and fand, and on good, if not the best, proportions of them.

When the ftones ufed in building were recently dug, or collected from the beds of rivers, the artifts needed no precautions against the bad effects of dry, bibulous, and dufty ftones or bricks; and their works had, of neceffity, every good quality attainable by the practice, which I commend, of foaking these materials. When their water was good, the cement, abounding in lime, was not much the worse for their ignorance of the ufe of lime water.

When the structure was intended to ftand by its own ftrength, rather than to depend on timbers; and was, by the folidity of its bearings and the diameter of its ftoney substance, fecured from agitation; when the thickness of the walls prevented the cement from being haftily dried, and afterwards fecured it from being thoroughly wetted; and when the enormous weight contributed to the approximation and cohesion of the parts of the cement to each other, and to the ftones: every defect of cementitious buildings, of a contrary defcription, was obviated by the nature of the ftructure; which rendered it as perfect, in the hands of any artists, as the most confummate fkill could make our modern, flender, tremulous, bibulous walls.' It will naturally be expected that Dr. Higgins fhould take notice of the reputed improvement lately made in the preparation of mortar, by M. Loriot, and publifhed by order of the King of France. With refpect to this difcovery (made public by order of his Majefty in 1774), we need fay no more to the Reader who is acquainted with the rationale of the process, as above laid down, than that M. Loriot ufes old flaked lime, that is, lime which has regained a part of the fixed air that had been expelled from it; and then, at the time of ufing the mortar,

adds

adds fresh powdered quicklime to the mafs. In short, not being acquainted with the true principles of the art, he corrects the bad quality of the old and effete lime, which conftitutes the bafis of his mortar, by the addition of fresh and non-effervescent lime, haftily added to it, at the time of ufing the compofition, and which muft undoubtedly improve the imperfect mass. On this fubject, the Author, very properly in our opinion, observes, that when an ignorant artist makes mortar with whiting inftead of lime, he can mend it confiderably by adding lime to it: but his mortar will ftill be defective, in comparifon with the beft that may be made, by reafon of the old flaked lime or whiting. For on repeated trials I found this to be the true ftate of the cafe *.'

Before we conclude this article, we should add, that the Author's obfervations and precepts do not merely reft on the fmall trials above mentioned, made with mortar spread on tiles, &c.; but that he has realifed them in practice, or on the great scale, particularly in incruftations, external and internal. Towards the end of this performance is given A Specification made in confequence of letters patent' granted to him; in which are minutely delivered the moft ufeful practical inftructions, deduced from the foregoing experiments and obfervations. We here learn too that the Author has fecured to Meffrs. James and Samuel Wyatt, architects, an exclufive right in his cement: intending to confine this privilege to them, till the public convenience requires its extenfion to others equally well qualified and difpofed to adopt his improvements in practice. With respect to his new cements employed in incrustations or ftucco, exceeding Portland ftone in hardnefs,' he refers the Reader to feveral houses in London and its neighbourhood, which he fpecifies; in which public trials have been made of his compofition, towards the end of the year 1778, and laft year; and adds that Meffrs. Wyatt are engaged to ftucco a great number of capital houses with it this fummer.- Thefe,' fays the Author, will be done in the highest perfection, because the workmen are now compliant, and experienced.'.

We cannot conclude this Article without obferving, that the public are much obliged to the ingenious Author for his meritorious attempts to improve an art in which they are fo much interested; and for communicating to them the refults of his numerous experiments, and the principles deducible from them. These principles, or at leaft a rational practice founded upon them, will foon, we hope, become known and familiar to the inferior artifts, fo as to conftitute a part of their routine.

*For our account of M. Loriot's publication relative to this fubject, fee Rev. vol. li. p. 184.

ART,

Art. VIII. Modern Anecdote of the ancient Family of the Kinkvervankot/darfprakengotchderns. A Tale for Christmas. Dedicated to the Honourable Horace Walpole. 12mo. I s. 6 d. Davenhill.

TH

HIS is the production of a fprightly mind, fomewhat of the Rabelaic caft. The ftory itself is rather a fimple one, and required very little invention as to plot, machinery, or denouëment. It is called a Tale for Chriftmas, and a perfon with a lively fancy and a voluble tongue, might have told it extempore for the amusement of a company over a good fire, on a Christmas evening.

Cecil is the beautiful daughter of a proud German Baron, who had nothing to boaft of but a long line of diftinguished anceftry. He was poor, but over full of the fentiment of familydignity, which was conftantly nourished by a fight of his family-pictures. Thefe covered every room of his caftle. They were the chief objects of his contemplation in foiltude; and in company the chief fubject of his converfation.

Franzel, the fon of a Farmer-general, a handfome young fellow, who bore a commiffion in the army, accompanying his mother on a vifit to the Baron, and conceived a strong paffion for his lovely daughter. The paffion was returned with equal warmth by Cecil. On a propofal of marriage by Madame Franzel, the Baron's pride difdained the connection of his daughter with a perfon not nobly defcended, however fuperior to himself in fortune. Cecil did not enter fo readily into her father's prejudices. She loved Franzel; and at all adventures was determined to marry the man whom her heart had chofen. Her father pointed to the family-pictures; but they could not convince her that her love was ill placed: there was an argument that preffed with greater force, and fpoke with an eloquence infinitely more affecting.

Hogreften, a relation of the Baron, and refident at the castle, had conceived an affection for Cecil. This gentleman was alarmed with jealoufy at Franzel's vifit; and was afterwards confirmed in his fufpicions of an amour, by an intercepted letter from Franzel to the young lady. This difcovery enraged the Baron, and mortified Hogreften. From a paffage in the letter, they concluded that Franzel would carry off the prize by ftratagem, or fome other means to prevent which, poor Cecil was doomed to imprisonment in a large room that had only two windows, which were fo near the ceiling, that it was impoffible for any one to reach them, even by getting on the chairs or tables.

In this confinement fhe was entrusted to the pious charge of the curate, who was inftructed to ufe his utmost endeavours to reduce her to the will of her father. She outwitted the curate,

and