214 ANNUAL OF SCIENTIFIC DISCOVERY. 



Sir H. Davy speaks of the same mineral color. He states that the 

 blue parts of the monument of Caius Cestus, and of the baths of Ti- 

 tus, at Rome, are done with this color. In an excavation made at 

 Pompeii, in 1814, in the presence of Sir H. Davy, he found a pot of 

 pale blue color, which he analyzed, and found to be a mixture of lime 

 and Alexandrian glaze. Davy did not give any quantitative analysis 

 of this blue color, but quoted the following passage from Vitruvius. 

 " The preparation of this blue color was originally invented at Alex- 

 andria, and Nestorius has since established a manufactory of it at Puz- 

 zola. Sand and flowers of natron (carbonate of soda) are first ground 

 together as fine flour, then mixed with copper filings, moistened with 

 a small quantity of water, and made into a kind of paste. It is then 

 heated in an earthen pot, placed in a furnace, so that the mass be- 

 comes fused, and gives rise to a blue color." It was with this glaze 

 that the Roman artists obtained all their shades of blue, by mixing 

 the finely powdered glaze with various proportions of chalk. The 

 beauty and solidity of this color, which resists the action of the most 

 powerful agents, and is not affected by air, light, or moisture, ought to 

 claim the attention of our painters and decorators, especially as it is 

 also cheaper than smalt, azure, or cobalt. It may be obtained by 

 strongly calcining for two hours, at a forge heat, a mixture of 60 

 parts of silicious sand, 45 parts of soda, and 9 to 10 parts of oxide of 

 copper. Chemist, Sept. 



Hcematinojie. Under the name of hfemalinone, a kind of glass was 

 in use with the ancients, for the purpose of making ornamental ves- 

 sels, mosaics, &c. It is described by Pliny, among others, and has 

 been found pretty abundantly in the excavations at Pompeii. This 

 glass is distinguished by its beautiful red color, which lies between 

 those of minium and of cinnabar. It is opaque, harder than ordinary 

 glass, susceptible of a fine polish, of conchoidal fracture, and its spe- 

 cific gravity is 3.5. By fusion it loses its red color, which cannot be 

 restored. Hsematinone contains no tin, or any other coloring matter, 

 besides suboxide of copper. All attempts of the moderns to imitate 

 it have hitherto entirely failed, but M. Pettenkoffer has at last suc- 

 ceeded in devising a method of producing this material in large quan- 

 tities, so that, with requisite precautions, it may be cast into plates 

 of any size, and worked into articles of every description. It is an- 

 ticipated that this discovery will furnish a clew to many of the pro- 

 cesses of the ancients in the manufacture of colored glasses, which 

 have hitherto baffled all research. 



CHEMICAL ANALYSIS OF A ROMAN PAVEMENT. 



A PAPER was presented to the British Association, by Professor 

 Buckman, on "some chemical facts connected with the tessellated 

 pavements discovered at Cirencester." The materials of pavements 

 are of two kinds, the first derived from the rocks of the district, and 

 the second composed of clay, glass, &c. The former or natural tes- 

 scllce are altered by chemical manipulation in various ways. The arti- 

 ficial tesscllce. consist of shades of red and black. In the Cirencester 



