(2) restriction of hours to six in summer and in winter to eight daily, with a two hours’ mid-day interval; (3) fortnightly examination of the workers; (4) air space per person of 40 cubic meters in the coating room and 30 in the drying room, and, in both, introduction of 60 cubic meters of air per head per hour; (5) Work to cease if the temperature of the room in summer reaches 25° C. Measures are necessary to prevent occurrence of mercury poisoning in hatters’ furriers’ processes (preparation of rabbit fur for felt hats) in consequence of the use of nitrate of mercury. Danger arises chiefly in cutting the hair, in dressing and drying, in sorting, and also in the subsequent stages of hard felt hat manufacture. Aspiration of the dust and fluff at its point of generation, isolation of the drying rooms and prohibition of entry into them while drying is going on, are necessary. In dressing (commonly known as ‘carotting’), the nitric acid vapour requires to be drawn away. In addition strict personal hygiene, especially of the teeth, is very important. Processes involving _water gilding_ (nowadays practised on a very small scale) should only be carried on in stoves provided with exhaust ventilation. Electroplating, fortunately, has almost entirely taken its place. As cases of mercury poisoning have been reported from use of mercurial pumps in producing the vacuum inside _electric incandescent bulbs_, air pumps should be substituted for them whenever possible. _Barometer_ and _thermometer_ makers may and do suffer severely if care is not taken to draw away the fumes and ensure good ventilation of the workrooms. Careless handling and the dropping of mercury on the benches make it difficult to prevent some volatilisation. Personal hygiene and especially a proper hygiene of the mouth are of the greatest importance in this class of work. Preparation of mercury compounds in chemical factories, especially the dry processes (sublimation), as in production of cinnabar, corrosive sublimate and calomel mixing, grinding, and sublimation, require to be carried on in closed apparatus. Preparation of the substances named above in solution involves much less risk than subliming. From our point of view, therefore, the former is to preferred. Arsenic, Arsenic Compounds, Arseniuretted Hydrogen For arsenic works imperviousness of the system and as complete condensation as possible are necessary to prevent escape of fumes. Respirators should be worn in manipulations with white arsenic, and such work as packing done under conditions of locally applied exhaust ventilation.