CEM

CER

( 281 )

The Maltha of the Greeks feems to have beenmore fimple than that employed by the Romanarchitects; at leafl we are informed that Panse-nus, the brother of Phidias , lined the infide ofthe temple of Minerva, at Elis, with a ftucco,in which the ufual materials (fand and lime) weremixed up with milk inftead of water, fome faf-fron being alfo added to give it a yellow tinge.The Roman Maltha, according to Pliny , k wasprepared in the following manner. Take frelhburnt lime, flack it with wine, and beat it upvery well in a mortar with hog’s-lard and figs :this cement if well made is exceflively tenacious,and in a fliort time becomes harder than ftone :the furface to which it is to be applied is to beprevioufly oiled in order to make it adhere.Another kind almoft equally ftrong and confide-rably cheaper was prepared by beating up to-gether fine flacked lime, pulverized iron fcales,and bullock’s blood. In the preparation ofmaftichs, as well as of every other kind of mor-tar, fo much depends on the manipulation, andespecially on the care which is taken to incor-porate the ingredients by long beating, that thofecountries in which labour is of the leaft valuepoflefs in general the bell mortar. Hence nodoubt principally arifes die unrivalled excellenceof the mortar made by the Tunifians and otherinhabitants of the northern coaft of Africa ,which, according to Dr. Shaw, is preparedin the following manner. One meafure offand, two of wood afhes, and three of lime,being previoufly fifted, are rfiixed together,and fprinkled with a little water; after the mafshas been beaten fome time a little oil is added :the beating is carried on for three days fuccef-fively, and as the evaporation in that hot climateis confiderable, the cement is kept at the properdegree of foftnefs by the alternate addition ofvery fmall quantities of water and oil. Thecement being compleated is applied in the ufualmanner, and fpeedily acquires a ftony hard-nefs. The laft fpecies of Maltha that we (hallmention is the celebrated chunam of India ,where it has been ufed from time immemorial.The method in which it is prepared at Madrasis as follows.*

Take 15 bufhels of pit fand, and 15 bufhelsof ftone lime, flack the latter with water, andwhen it has fallen to powder mix the two in-gredients together, and let them remain un-touched for three days. In the mean timediffolve 20 lbs. of molafles in water, boil a peckof gramm (a kind of pea) to a gelly; boil a peckof mirabolans alfo to a gelly, mix the three

k Hill. Nat. lib. oh. 53. 1 PliiLTrank xixvii.

VOL. I.

liquors and incorporate part of the mixture veryaccurately with the lime and fand, fo as to makea very fluid cement: fome fliort tow is now to bewell beaten into it, and it is then fit for ufe.The bricks are to be bedded in as thin a layer aspoflible of this mortar, and when the workmenleave off, though but for an hour, the partwhere they recommence working is to be wellmoiftened with fome of the above liquor beforethe application of any frefli mortar. Whenthis is ufed for ftucco, the white of four or fiveeggs, 4 oz. of butter, or fefamum oil, and apint of butter-milk, are to be ground up withevery half bufliel of cement, and the mixture isto be applied immediately.

It is to be regretted that no experiments haveas yet been inftituted to afcertain the caufe ofthe induration of calcareous cements: it is obvi-oufly not owing to the abforption of carbonicacid, becaufe in numerous inftances the cementhardens long before the lime is faturated: in thedifferent kinds of maltha the lime combines withtire albumen, mucilage, and oil, with which it isin contact, and in all probability takes up littleor no carbonic acid, and if it is true that thelime in old mortar cannot, by burning, be re-converted into quicklime, it may reafonably bequeftionedwhether, even in the fimple calcareouscements, carbonic acid acts fo important a partas is ufually attributed to it.

CERUMEN, or Ear Wax.

This fecretion is known to be a yellow glu-tinous fubftance, extremely bitter, which is al-ways contained in greater or lefs quantity in thecanal from the external ear to the tympanum.By the analyfis of Vauquelin ra it appears to beconfiderably combuftible, and largely folublein alcohol; the refidue not acted on by thisliquor readily unites with alkalies. It appearsto be compofed of a fat oil refembling that ofthe bile; of an albuminous mucilage; and ofa peculiar colouring matter, in which alfo thebitternefs feems to refide. The quantity col-lected was too fmall for a more accurate ex-amination.

The ufe of the ear-wax is not precifelyknown, but a due quantity of it feems effentialto the fenfe of hearing. It is readily foftenedby ftrong foap and water, which forms a goodinjeCtion to loofen it from the ears when it hascollected in too large quantity, a very commoncaufe of deafnefs.

CERUSSE, or White Lead , is a white oxydof this metal prepared by the vapour of vinegar.See Lead.

p. *31, ■> Fourcroy Sylt. des Connoiff, Chinn

2 N