The movement of the gases through all this complicated set of apparatus is produced by a Root's blower placed at the end of it all.
Over to the blower proper.
The blower then heats the end of the cylinder again and rapidly spins the pipe about its axis; the centrifugal effect is sufficient to spread the soft glass at the end to a radius equal to that of the rest of the cylinder.
The blower places the glass in the mould, closes the mould by pressing a lever with his foot, and either blows down the blowing iron or attaches it to a tube connected with a supply of compressed air.
When the air has forced the glass to take the form of the mould, the mould is opened and the blower gives the blowing iron with the bottle attached to it to the " wetter off."
The results given below, which are selected from a much larger series published in the Journal of the Chemical Society, were obtained by heating samples of the different coals in vacuo for several hours at the temperature of boiling water: - In one instance about i% of hydride of ethyl was found in the gas from a blower in a pit in the Rhondda district, which was collected in a tube and brought to the surface to be used in lighting the engine-room and pit-bank.
It is by the appearance of the flame that the operator or " blower " knows when to end the process, judging by its brilliancy, colour, sound, sparks, smoke and other indications.
The delay which this test causes is so unwelcome that in all other countries the blower continues the blow until decarburization is nearly complete, because of the very great accuracy with which he can then read the indications of the flame, an accuracy which leaves little to be desired.
The oxidation of manganese is capable of generating a very high temperature, but it has the very serious disadvantage of causing such thick clouds of smoky oxide of manganese as to hide the flame from the blower, and prevent him from recognizing the moment when the blow should be ended.
The blower therefore stops the process when he has blown a predetermined quantity of air through, counting from the drop of the flame; but as a check on his forecast he usually tests the blown metal before recarburizing it.
The hot water from B, freed from tar, is pumped into a third tower C, through which cold air is forced by means of a Root's blower by the pipe w.
Dean managed to whistle down a young boy who agreed to use his snow blower on Dean's unfinished sidewalk, for an amount Dean considered ridiculous, but he knew he needed to get up to snuff on Shipton's fall before he was totally on the defensive.
The blower repeatedly heats the lower part of the mass of glass and keeps it distended by blowing while he swings it over a deep trench which is provided next to his working platform.
The lower end of the cylinder is opened, in the case of small and thin cylinders, by the blower holding his thumb over the mouthpiece of the pipe and simultaneously warming the end of the cylinder in the furnace, the expansion of the imprisoned air and the softening of the glass causing the end of the cylinder to burst open.
These are almost invariably air furnaces, though sometimes air under pressure is used, as, for example, in the combustion of small anthracitic coal, where a current of air from a fan-blower is sometimes blown under the grate to promote combustion.