chiefly Chemical. 259 



held in solution in the sea, owing to the higher temperature 

 of the shores, and the agitation of the breaking waves, it 

 constitutes the cementing principle of all the sandstones now 

 in the act of forming at the sea-margin in various regions. 

 Absorbing carbonic acid slowly from the atmosphere when 

 lime is mixed with siliceous or shell sand, and properly mois- 

 tened, it appears to operate in the same manner in forming 

 in time a mass of stony firmness. When a foreign substance 

 is not present, and hydrate of lime is converted into carbo- 

 nate by the absorption of carbonic acid, then it appears to 

 form a soft little cohering mass of granular particles resem- 

 bling chalk. I have found instances of the kind in the pure 

 lime-mortar used in the Coliseum, and in the walls of ancient 

 Thebes in Egypt. Whilst the mortar, a mixture of lime and 

 sand, employed in the rubble work, of which the Coliseum 

 — a combination of arches consists — is now hard as stone, 

 this pure mortar, consisting only of carbonate of lime, used 

 as a cement for the facing stones of the building, is as soft 

 as chalk ; and the same remark applies to the pure mortar 

 similarly used at Thebes. 



5. In examining specimens of manures offered for sale as 

 guano, it is desirable to have a ready test of sulphate of lime 

 by which it may be distinguished from the phosphate. The 

 insolubility of the latter in water, and the moderate degree 

 of solubility of the former, are certain criteria. Some time, 

 however, is necessary to witness the effect in a satisfactory 

 manner. To obviate delay, I find the following process to 

 answer well. After well washing the sample under exami- 

 nation, to remove the more soluble salts, distilled or rain 

 water is to be poured on the residue, and a minute or two 

 after a few drops of the solution of oxalate of ammonia are 

 to be added ; if sulphate of lime is present, a cloudiness will 

 be perceived apparently rising from the bottom, the cause of 

 which requires no explanation. 



6. Ammonia, as it is well known, precipitates from an acid 

 solution several substances, as alumine, magnesia, phosphate 

 of lime, phosphate of magnesia. The appearance of the pre- 

 cipitate indicates tolerably its nature, and, consequently, is 

 deserving of attention. The precipitate of alumine alone is 



