518 FURNACE " 



munication "with 0110 another. Into the upper chamber, gas is allowed to pass by the 

 tube marked AS. Into the lower chamber, air is forced by the tube marked' A IK. 

 1QOfi The upper part of this burner is an inch thick in 



the metal. Through this solid roof holes from 6 to 

 26 in number are bored for the escape of the gas. 

 The number of holes depends, of course, upon tho 

 hi-ating power ivquiivd from ilm bimi.-rs. Tho 

 air passes from the lower chamber, through a 

 series of metal tubes, placed in tho centre of tho 

 gas-holes, and continued to tho surface of tho 

 burner, so that the gas and air do not mix until 

 both have left tho gas-burner, and then a current, 

 of air is blown through tho middle of cacli jet of 

 gas. Tho bottom of tho gas-burner is made to 

 unscrew, and the division between tho two 

 chambers, which carries the air-tubes, is easily 

 removable for the purpose of being cleaned. Tho 

 gas and air pipes generally used in tho inventor's experiments wore each half an 

 inch in tho bore and ten inches long ; the gas had usually a pressure of half an inch 

 of water, and tho blast of air about ten times that pressure. Tho quantity of gas 

 used in an hour was about 100 cubic feet. The stopcock which supplied it had a 

 bore of half an inch. The round rod represented at the bottom of the burner, Jig. 1008, 

 is intended to fit it to tho support. 



When the gas is lighted and the blast of air is put on, tho flame produced by tho 

 gas-burner is quite blue, and free from smoke. It is two inches in diameter and 

 three inches high, and the point of greatest heat is about two inches above tho flat 

 face of the gas-burner. Above this steady blue flame there rises a flickering ragged 

 flame, several inches in height, varying with the pressure of tho gas. In tho bluo 

 flame, thin platinum wires fuse readily. 



When tho gas is burning in this manner, and the apparatus is attached to flexible 

 tubes, tho burner may bo inverted or held sideways, without disturbing the force or 

 regularity of tho flame, so that the flame may bo directed into a furnace at tho bottom, 

 the top, or the side, as circumstances may require. 



The following articles are used in building-up the gas-furnace for different experi- 

 ments. They vary in size according to the volume of tho crucible, or the weight of 

 the metal to bo heated : 



1. A circular plate of fire-clay, two inches thick, with a hole in tho centre, 

 exactly fitting the upper part of tho gas-burner, which is made to enter into tho 

 hole three-quarters of an inch. In external diameter, this clay plate agrees with each 

 size of tho furnace. 



2. A cylinder of fire-clay, of which two pieces are required to constitute the body 

 of each furnace. In the middle of each cylinder a trial holo is made, one inch in 

 diameter, to which a fire-clay stopper is adapted. 



3. A fire-clay cylinder, closed at one end, and pierced near tho open end with six 

 holes of half an inch in diameter. The thickness of the clay is immaterial. This 

 cylinder is three inches in diameter. 



4. A circular plato of fire-clay, two and a half inches or three inches in diameter 

 and one inch thick. Similar pieces half an inch thick are useful. 



5. A cylinder of plumbago, to be used as a crucible support. It is throe inches in 

 inside diameter, one inch in height, and pierced with twelve holes of three-eighths 

 of an inch boro. 



6. A similar cylinder of plumbago, two or three inches high, pierced with twenty- 

 four holes of three-eighths of an inch bore. 



7. A thin plate of plumbago, three inches in diameter, viz. of tho samo diameter as 

 tho cylinder of 5 and 6. It has a small holo in the middle, and being of soft material, 

 the holo can be easily cut or filed to suit crucibles of any desired size. 



To suit the larger kind of crucibles and furnaces, cylinders aro niado resembling 

 tho above in form, but of greater diameter. 



As in all cases the heating power of the gas-fiirnaco spreads laterally and does 

 not rise vertically, tho most advisable form of tho crucibles required for use in ir. is 

 short and broad, not tall and narrow, and tho supporting cylinders nnist be shaped 

 accordingly. No fire-bars or grates must bo used to support tho crucibles in this gas- 

 furnace, because no material formed into narrow bars can sufficiently withstand its 

 power of fusion and combustion. 



8. A plumbago cylinder, or crucible jacket, two and a half inches high, two and a 

 half inches in diameter, and a quarter of an inch thick in the walls. It has six holes 

 of three-eighths of an inch diameter near one end. 



