The Jernkontoret of Sweden is an ironmasters' exchange at Stockholm, which was founded in 1747 for the financial convenience of the subscribers, and now possesses a reserve fund of about $1,500,000. The functions of the society have been considerably enlarged since its institution. It has organized a corps of mining engineers and metallurgists, who receive salaries from it, and further from manufacturers whom they may serve. They are often commissioned to go abroad and obtain information and practical hints bearing upon their profession. The institution is supported by a light assessment on the production of its constituency. It has a fine building, and publishes an annual volume in _Jernkontorets Annalen_, containing original memoirs and reports from technical agents, which is sent gratuitously to all the masters of forges in Sweden, and is sold abroad. In a number of glass mirrors of the third and fourth centuries, examined by M. Berthelot, the glass was coated with a metallic substance and with a layer of whitish material. The metal proved to be lead, with no trace of gold, silver, copper, tin, antimony, or mercury, and no sign of organic substance was present. It was thus shown that no extraneous material was used to cement the lead to the glass. The mirrors appeared to have been cut from hollow blown glass globes, and it is possible that before the globe was cut the molten lead had been poured into the interior, and had adhered to the previously warmed glass. The whitish layer consisted of lead carbonate and lead oxide formed by the oxidation of the lead coating and calcium carbonate, which had been deposited from the water of the district in which the mirrors were found.