VARIETIES OF AGATE, ETC. 141 



posed by the sulphuric acid, and a deposit of carbon pro- 

 duced. Colourless banded agates are in this manner changed 

 into onyx with black or dark brown and white layers. The bluish- 

 white chalcedonies are changed in the process by heat to almost 

 pure white ; and perhaps the contrast of colour causes the white 

 bands to appear whiter than they really are. 



The sard or red tint is produced by soaking colourless or grey 

 chalcedony in a solution consisting of nitric acid, water, and iron, 

 and then heating it. Blue, green, and yellow tints are also pro- 

 duced by chemical means, the colour depending upon the salt in 

 which it is boiled and the re-agent used to precipitate the colour 

 required. Deep colours can be reduced by the action of nitric acid. 



The principal colouring matters in agates, as found in nature, 

 are various oxides of iron and manganese, and probably chrome. 

 Polished stones, agate, onyx, sardonyx, etc., are made into orna- 

 mental articles of various kinds by German, French, Italian, and 

 other lapidaries, as brooches, bracelets, beads, seals, snuff-boxes, 

 small vases, paper-knives, handles for knives and forks, etc. The 

 common agates are used in leather dressing, paint-pounding, etc., 

 and for mortars for chemists to pound their drugs in. 



In Eastern countries they are used for inlaying in marble 

 pillars, cornices, and other portions of palatial buildings. Mr. 

 Forbes, in his Oriental Memoirs, says : — " I was delighted with 

 the mausoleums of Botwab, though they are inferior to those at 

 Agra and Delhi, where imperial wealth and magnificence had 

 united to decorate the tombs of the Mogul princes and their 

 favourite sultanas, the ornamental parts being entirely composed 

 of agates, carnelians, turquoises, lapis-lazuli, and other valuable 

 gems."' 



On the restoration of Crathie Church — where the Queen and 

 Royal Family occasionally attend during their residence at Bal- 

 moral—a polished granite pulpit was erected during the present 

 year (1895), which is inlaid with agate pebbles collected on the 

 shore in the island of lona by Princess Louise, Marchioness of 



Lome. 



Agate Superstitions. 



Camillous Leonardus, M.D., 1502, says :— " It subdues the 

 poison of vipers, and scorpions if bound on the puncture, or 



