are located in close proximity to the metal vapor exhaust holes 70 as required the mandrel plates may be held in place temporarily while the cover plate 34 is put into place and the furnace is covered the furnace is then sealed and connected to the exhaust system not shown the cvd region of the furnace and the retort region are heated to operating temperature the flow of reaction gas 38 and the inert carrier gas such as helium neon argon krypton or nitrogen is initiated solid metal 42 is then fed to the retort 54 the ratio of the gas flow rate of the reaction gas 38 to the feed rate of the solid metal 42 is maintained at approximately stoichiometric ratios the chemical vapor deposition process is then monitored by appropriate means known in the art when the chemical vapor deposition process is completed the furnace is cooled and the cvd furnace is then opened and the cvd deposited material is removed for inspection and finishing of the final product thus in accordance with the invention there has been provided a method and a device which to provide a controlled supply of metal vapor to a cvd reactor for reacting with a reaction gas to form a chemical vapor deposited structure there has also been provided a method and a device which provide a constant supply of metal vapor to a cvd reactor for reacting with a reaction gas to form a chemical vapor deposited structure there has also been provided a method and a device to which permits an accurate determination of the rate at which.