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med to it, we so little mind in the use of gypses or pkiler."
ally performed, must have observed many instances of that sort of sudden desiccation,—but without perceiving any of the other effects here mentioned.
In flaking lime-stone, especially when of the purest sort, so much water is necessary, and it is imbibed so slowly, that the operators, knowing it will be all drunk up in due time, often throw so much on one place at once, as to reduce it to almost a fluid state. —This water soon sinks through it to the unslaked lime below.—But, if the lime on the top was regularly flaked before the last effusion of water, it retains a smooth uniform surface like plaster,—is dried almost entirely in a few minutes,—and, if not broke by the swelling os the lime below, continues ever afterwards to retain that form without crumbling away at all. If this is allowed to dry perfectly, and no more water is poured on it till it has absorbed al! its ir, it js perfect chalk. It has the fame hardness, consistency, &c. and cannot be distinguished from it, either in appearance or by any other property.
This, however, will never be the cafe, unless the lime has been perftctly pure, so as to dissolve in acids as entirely as sugar does in water
If I understand this paragraph, it means neither more nor less than that these two substances unite, because they necessarily do unite most perfectly.—If it has any other meaning, I am dull enough not to perceive it.
It would be tiresome to quote more passages from this treatise. Let it suffice to observe, that the author proceeds to tell, that this newly discovered cement dries and hardens almost under the hand of the operator, without cracks or flaws of any fort * ;—that it neither expands nor contracts with the air f ;—that it is impervious to moisture J,— and may not only be employed for making roofs to houses that are subjected to the continual dropping of water ||, basons, aqueducts, canals §, &c. that will instantly contain water in any quantities,—but even finer works of the pottery kind f ;—that it perfectly resists frost; with a long et caetera of other
t t qua
qualities which it would be tiresome to enumerate: For an account of which I must refer to the pamphlet itself.
That Monsieur Loriot has not discovered a cement possessing these peculiar qualities, it would be unbecoming in me to deny; seeing it is affirmed, that works have been erected with it that prove the facts in the clearest manner. But, that such effects will be invariably produced, merely by adding a certain proportion of unslaked Jime in powder to mortar, as he asserts, or even by making she mortar entirely with powdered quicklime, I may, without hesitation, venture to deny, not only from the reasoning above given, but from actual experiment again and again repeated by myself; which is likewise, in some measure, corroborated by the experience of Mr Doffie *.
* Although Mr Doffie recommends his new discovered cement for many qualities, yet he differs extremely from Mr Loriot in his account of the man«
For these reasons, I am induced to think lhat, if Monsieur Lariot has really experienced these uncommon effects from the mortar he has tried, it must have been occasioned by some other unobserved peculiarity, and not merely by the circumstance to which he seems to ascribe it.—Possibly it may have been impregnated
ner in which the union is effected. For, instead of saying that * it consolidates as readily as metals in • fusion when newly taken from the fire,' he fays it continues soft for some time, and only gradually hardens in the air. See Doffie's Msm. of Agriculture, vol. 2. p. 20.
Mr Doflie. does indeed ascribe to his cement some of the fame qualities that Mr Loriot attributes to his. —Some of these, however, are common to every sort of lime-mortar when carefully made; and, were it not a little foreign to our subject, it would be no difficult matter to show in what manner an inexperienced person might have his judgment misled with regard to some of the other qualities that may be called more equivocal The imagination is a more powerful magician than all the wife men of Egypt!
pregnated with gypsum^ a saline substance, naturally abounding in France; and, as one of its principal ingredients is lime-stone *, there is nothing extraordinary in its being found in the same quarry chrystallized along with the lime-stone ; nor any impossibility of its escaping undecomposed on some occasions during the calcination of the lime.—Or, it may perhaps have been otherwise accidentally mixed with the lime in these experiments.
But, in whatever way the gypsum may come there, if it be present, it is not to be doubted but effects, similar in kind ^ though not in degree,) to what Mr Loriot describes, would in some measure result from the practice he recommends. For, \$ gypsum be deprived of its moisture by calcination, it becomes a fine powder, greatly resembling the
* Gypsum is an earthy salt, consisting of the vitriolic acid and calcareous earth.—It is best known among artizans by the name of piaster of Paris.