L. TECHNOLOGY. 533 



ing the exhibition international congresses will be held for 

 the discussion of important questions, to which either the 

 exhibition itself may give rise, or for which it may furnish 

 materials for illustration. 12 A, September 28, 1871, 434. 



ARTIFICIAL GRINDSTONES. 



A new application of the method of manufacturing arti- 

 ficial stone by the Ransom process, lately introduced, con- 

 sists in substituting emery for sand, by means of which emery 

 disks of great hardness are now constructed, which are doing 

 excellent service in sharpening saws and other implements. 

 15 A, November 11, 1871, G28. 



COLORING OF CEMENTS. 



The ordinary coloring matters used in cements or plaster- 

 ing usually injure the setting power more or less, and fail to 

 produce pure tints. According to a German chemist, how- 

 ever, cheap and permanent color washes may be made by 

 mixing equal volumes of the dry pigment and burned and 

 washed flint with milk of lime, a little water-glass being ad- 

 vantageously added. The tint produced is very agreeable, 

 and, if stable mineral colors be used, as durable as the cement 

 itself. Surfaces of great beauty are produced by finely pow- 

 dered marble and flint, with the faintest tint of chrome green. 

 The wash should be applied as soon as possible after the ce- 

 ment has set, and, if practicable, in one coat only; but, if two 

 are necessary, the second must be made with the addition of 

 water-glass. It is indispensable that the work be freely wetted 

 for a week after laying on the color. 21 A, June, 1871, 451. 



CEMENT FROM SOLUBLE GLASS. 



A cement of great hardness, and of great applicability, it 

 is reported, is made by mixing different bases with soluble 

 glass. Combined with fine chalk and thoroughly stirred, it 

 will produce a hard cement in the course of six or eight 

 hours ; with fine sulphide of antimony, a black mass is pro- 

 duced which can be polished with agate, and then possesses 

 an excellent metallic lustre. Fine iron dust gives a gray- 

 black cement. Zinc dust produces a gray mass exceedingly 

 hard, with a brilliant metallic lustre, so that broken or de- 

 fective zinc castings can be mended and restored. A white 



