Sept. 1, 1864.] THE TECHNOLOGIST. 



MACHINERY FOR THE MANUFACTURE OP PLATE GLASS. 59 



glass can now be annealed in each oven, compared with what was formerly- 

 considered possible ; and consequently a large outlay in building and 

 in space has been saved, since only one layer of plates can be placed 

 in the oven at one time, no method of piling the plates being consi- 

 dered practical, or even safe. The chemical difficulties and manipula- 

 tion in producing the raw material have thus been very satisfactorily 

 overcome ; but the problem of carrying out the necessary improve- 

 ments in the subsequent mechanical operations has not, perhaps, been 

 so completely solved, though considerable strides have been made in 

 that direction also. 



The plates of glass, when taken from the annealing ovens, are 

 exceedingly irregular, particularly on the surface which has been upper- 

 most in the process of casting, that surface being undulated or wavy 

 after the passage of the roller over it whilst in a semi-fluid state ; the 

 lower side, too, is affected by any irregularities on the surface of the 

 casting table, and also to some extent by the floor of the annealing oven ; 

 and both sides of the plates are also covered with a hard skin, semi- 

 opaque. The plates vary in size, the largest being about 17 ft. long by 

 9£ ft. wide ; and the thickness varies according to the size from 3-8ths 

 to 5-8ths in. The first process to which the plates are submitted is 

 that of grinding, to take off the hard skin and reduce the surface to a 

 uniform plane, which is performed by the application of sand and 

 water. The second process is that of smoothing, which is a continua- 

 tion of the first process, but performed with emery of seven different 

 degrees of fineness, so as to prepare the surface of the glass for the final 

 process of polishing. This last process i3 affected by the use of oxide 

 of iron employed in a moist state. 



The machine in general use for grinding is that which was originally 

 employed at the commencement of the glass manufacture, and is be- 

 lieved to have been designed by James Watt. It is known by the name 

 of the " fly frame " machine". It consists of two benches of stone, suf- 

 ficiently large to hold a plate of glass, and placed about 12 ft. apart ; 

 on these benches the plates of glass are fixed by plaster of Paris. Each 

 bench has a runner frame made of wood, about 8 ft. long by 4^ ft. wide, 

 shod on the underside with plates of iron about 4 in. broad and J in. 

 thick, and provided with a strong wrought-iron stud on the upper side, 

 by which it is moved about over the surface of the glass. The gear- 

 ing for driving these two runner frames is placed between the two 

 benches, and consist of the square cast-iron fly frame, with two flat 

 bars hinged to it on opposite sides, extending over each bench, and sus- 

 pended from the roof by long chains, so as to allow them to radiate 

 freely in every direction ; this is called the " fly frame," from the pecu- 

 liar motion given to it, and each of the runner frames is connected to 

 it by a central stud, working loosely in the slot between the bars. The 

 fly frame receives its motion from an upright spindle, which is driven 

 from the main line of shafting by a pair of level wheels with a fric- 



