Samples of fume condensed as a grey powder, and collected by Collis from different kinds of prolongs, showed 1·3 to 2·7 per cent.[7] of metallic lead respectively, and a sample of dust deposited from material containing 10 per cent. of lead, 3·25 per cent.[8]. =Manufacture of Red and Orange Lead and Litharge.=--These processes are frequently carried on as part of lead-smelting works. Red lead is produced by oxidation, first, of metallic pig-lead, in a reverberatory furnace at dull red heat, into massicot (yellow monoxide). During the process the material is constantly raked. The massicot is withdrawn from the furnace, and subsequently, after drying and sieving, is again subjected to similar treatment at slightly lower temperature. Orange lead is made by treating white lead in the manner described. During the ten years 1900-1909 the number of reported cases from the manufacture of red lead was 108, of which 47 were attributed to work at the furnaces, 43 to packing and sieving, and 16 occurred among general labourers, part of whose duty it was to sweep up the floors. Collis estimates the attack rate in the five years 1905-1909, in a certain number of factories employing 171 persons, at 50 per 1,000. Reference to the table on p. 48 shows that the proportion of those suffering from encephalopathy is higher than in any other industry--an observation previously noted by Layet[9]. _Dangers and Prevention._--Danger is practically limited to escape of dust in (1) raking the charge out from the hearth on to iron trolleys, (2) sieving, and (3) packing. In all these operations exhaust ventilation is essential, and for sieving and packing the installation requires to be designed with especial care, so as to be able to keep within the sphere of the exhaust the spading and shovelling of the material, in very fine state of division, into the cask. Sometimes the material is elevated from pits, and eventually packed by mechanical means into barrels resting on a jolter. Unless the elevators are quite dust-proof, and the collar hermetically seals the connection of the shoot with the barrel, the vibration of the heavy machinery and pressure of air inside the casing will cause dust to escape.