_Type-Casting._--In letter founding and in the monotype letter-casting machine the molten metal, heated by a coal fire in the former and Bunsen burner in the latter, at regular intervals fills the matrices at a point where it is cooled by a jet of compressed air, and the formed letter is then mechanically ejected into a receptacle. The temperature of the molten metal has to be carefully regulated, and does not usually rise above 400° to 450° C.--a temperature at which it is extremely doubtful if lead fume can be produced. Sommerfeld[11] states that in 60 cubic metres of air aspirated close to a type-casting machine no trace of lead was found, because vaporization does not take place below 550° C. Such skimming as must occasionally be made of the small surface of molten metal is in a slaggy state, and does not appear to contain much oxide. This is deposited usually in a small box and removed to be remelted once a day. What fume, often of unpleasant odour, is noted is probably due to acroleic acid vapour from the grease and dirt. The letters having been cast, the type may be rubbed on sandstone or on a file, by which small quantities of metallic dust are given off; set up on setting-boards so that all letters face the same way (work on which female young persons are usually engaged); certain portions of letters undercut so as to make them lie perfectly parallel; dressed, planed, and examined, so as to be of precisely the same height; and finally assorted into founts and packed in the warehouse. In all these operations the fingers necessarily get blackened by contact, and there must be slight dislodgment of metal particles to account for the cases reported.