998 Transactions of tue American Institute. 



Steam Road-Roller. 



The huge machine used for levehng the carriage-way in some of 

 the streets of Liverpool, England, has so injured the network of gas 

 and water-pipes underneath, that the corporate authorities find that 

 they must greatly decrease its weight, or cease using it altogether in 

 certain parts of the town. 



The Bleaching of "Wood Pulp. 



The objectionable results of the process of bleaching by chloride of 

 lime are, that any excess of the chloride has a tendency to produce a 

 yellow tint, that all strong acids are apt to turn the paste red under 

 the action of the sun, or sometimes solely by the presence of moisture; 

 that the smallest trace of iron will blacken the paste in a short time. 

 These difficulties have been obviated by M. Orioli, of Paris, who mixes 

 with every 100 kilogrammes of wood pnlp 800 grammes of oxalic 

 acid, which serves the double purpose of bleaching the coloring mat- 

 ter already oxydized, and of neutralizing the alkaline principles favor- 

 able to oxydation ; two kilogrammes of sulphate of alumina are added, 

 forming with the coloring matter of the wood a nearly colorless lake, 

 which enables the brilliancy of the product to be heightened. 



Enameling of Ikon. 



The process of enameling cast or wrought iron most commonly 

 used is to cover the previously well cleaned and smooth surface of 

 the metal with finely pulverized enamel or glass, and subject it to a 

 high heat in a muffle or oven, by which the fused coating is made to 

 adhere more firmly to the metal. To secure this adherence a new 

 plan has been proposed in Germany by Mr. Ballouhey, which is to 

 first oxydize the surface of the iron, forming the protoxyd and sesqui- 

 oxyd of iron by pouring upon it the hot liquid material forming 

 white glass, or by placing the material in powder upon the metal and 

 vitrifying it by heat. In this case the silicate of iron is formed 

 which is said to unite more firmly with the metal. This plan may. 

 be an improvement over the old one, but it is plain that the great 

 difficulty in adherence arises from the diflference in the expansibility 

 of the metal and the enamel, and is one that cannot be entirely 

 obviated. 



Market Approaches. 



A correspondent of The London Builder suggests that every new 

 mai'ket erected should practically carry out two leading principles ; 



