544 REPORT OF NATIONAL MUSEUM, 1893. 



alabaster was derived was uhL-ianrfxtz^ or iu.(i;ia(yTp«'^^ aud is said to have 

 been derived from a^ not, aud hx'flr,^ a handle, or yjj-i^^r-', to hold, in allu- 

 sion to the little handleless, phial-like, or amphora- shaped perfume 

 vessels eoustructed from it. But the word after a time passed from the 

 thing made to the substance of which it was made, though Pliny men- 

 tions an Egyptian town called Alabastron, where the manufacture of 

 the vessels was carried on. The ancient Eoman name of the stone wa? 

 alabastrites.* Be this as it may, the name alabaster, as now used by 

 all authorities, applies only to a white, though sometimes variously 

 veined and mottled variety of gypsum, a calcium suli»hate, while the 

 onyx marbles with which we have to do in this work, are of calcium 

 carbonate and mineralogically either aragonite or calcite, principally 

 the latter, 



ORIGIN AND MODE OF OCCURRENCE. 



The origin of these stones is purely chemical, and of interest on 

 account of the very simplicity of the process. Simple aud well known 

 though it may be, we are apparently not yet able to account in a 

 manner entirely satisfactory for the varying physical conditions, as 

 texture and hardness or form of crystallization, under which the mate- 

 rial occurs. Pure water, although an almost universal solvent, never- 

 theless acts so slowly upon most substances belonging t% the mineral 

 kingdom that the results are quite inappreciable to the ordinary 

 observer. When, however, holding minute quantities of carbonic acid, 

 and especially when, as deep in the surface of the earth, it is under 

 considerable pressure, its solvent property is very considerably aug- 

 mented, and results are produced both in the way of solution and 

 redeposition which are readily noticeable, even to the most casual 

 observer. 



One of the most common mineral substances found in aqueous solu- 

 tion is carbonate of lime, the essential constituent of ordinary limestones 

 and marbles, as well as of the beautiful onyx marbles, as we shall 

 notice later. It is to be found in the water of all springs, streams, 

 lakes, and seas, aud furnishes the means whereby the uniltitudinous 

 shellfish aud corals build up their calcareous shells and skeleton-like 

 supports. Pure water will dissolve only 1 part in 10,800 when cold 

 and 1 part in 8,875 when boiling. When the water is saturated with 

 carbonic acid gas at ordinary atmospheric pressure and a temperature 

 of 10° C, its capacity for solution is increased to nearly 1 part by 

 weight in 1,000 (0.88 grams per liter of water). With an increase in 

 pressure the amount of carbonic acid that can be held by water is 

 also increased, and there is as a natural result an augmentation in its 

 solvent power. The maximum amount of lime which can be dissolved, 

 even under the most fiivorable circumstances, is stated by Roscoe and 



*JoxES, T. Rupert. Demonstratiou oh the marbles aiitl other monumental stones 

 in the British Museum.— (Proceedings Geologists Association, Vol. vin.) 



