=Block Paper and its Uses.=--[J. B. GAUSBY.]--(B. 574.) Since the previous paper on this subject was written, there has been no alteration in the process of manufacture, nor has there been any marked development of the trade as a whole. The manufacture of panels of various thickness has increased in consequence of their adoption in the place of wood, where bending or exposure to varying conditions of moisture are required. The great quantities of trays imported from Japan for some time checked the demand for moulded paper tray blanks, but the demand is now returning. Fashion has however dealt less kindly with the manufacture of slabs in blocks for the purpose of manufacturing artificial jet ornaments. This branch of the trade is entirely destroyed. =Boiler Plate and Gas Holders.=--[W. S. SUTHERLAND.]--(B. 93.) In spite of heavy duties, boiler and gas apparatus are still exported. Within the last twenty years many types of tubular boilers have been introduced, but the one fluted or Cornish boiler, the simple egg-end, and the Lancashire and double boiler with cross tubes are most generally used. Mild steel has been introduced into boiler making and plate making during the last few years, though it is still a contested point whether it is superior to iron when all things are taken into consideration. It requires to have all rivet holes drilled, and it must be carefully annealed, though the writer is informed by Mr. Edwin Danks, of Oldbury, that steel makers often prefer to have their plates either worked cold or at a red heat, and not in the intermediate condition. Drilling machines especially designed are now used. Hydraulic machines of greatly improved construction have come into use for facilitating the operations in the boiler yard. These machines are portable, the water being supplied through a flexible tube. Improvements in the construction of the internal boiler flues have been made to enable them to resist increased pressure, and further to allow the expansion and contraction of the flue without injury. Of these improvements, the most noted are Fox’s corrugated flues, the bowling ring, the flanged flue, and Arnold’s flue. An improvement introduced by the writer into boiler plate working, is the system of welding by gas, adopted in Birmingham by Messrs. Piggott, and by Messrs. Lloyd and Lloyd, for tubular and other work and applied by Mr. Puplett for welding plate sheets of steel only, 12 and 13 w.g. thick into ice moulds. It is found that the strength of the weld equals that of the solid plate, and the process is a cleanly and convenient one. Hemispherical sugar pans of 8 and 9 feet diameter without a joint are made by Messrs. Piggott, who use this process. _Gas Holders._--Since 1865 much larger gas holders have been made. The two designed by Mr. Hunt, and recently erected at the Windsor Street Works, Birmingham, have each a capacity of 6,000,000 cubic feet, and are at the present time the largest in the world.