Sept. 1, 1864.] THE TECHNOLOGIST. 



THE MANUFACTURE OF PLATE GLASS. 61 



motion given to them by the bar, and are not left free to revolve 

 round their own centres as in the grinding operation previously de- 

 scribed. The centre of the bar between the two runner frames is kept 

 in position by a radius rod secured to a fixed bracket on one side of 

 the bench, at right angles to the direction of the bar. The crank being 

 set in motion, the bar and runner frames receive a movement somewhat 

 similar to the figure 8, which is very similar to the motion given in 

 manual labour. One advantage of this machine is that two surfaces 

 of glass are finished at one operation. The space between the two 

 runner frames is found very convenient for applying the emery, and 

 also ascertaining the progress of the work, without having to stop the 

 machine. 



The machinery used in the polishing process remains the same in 

 principle as that originally constructed for the purpose. Each machine 

 consists of a strong cast-iron frame, about 18 ft. long by 10 ft. wide, con- 

 taining a series of small rollers, upon which is placed a wooden table 

 with two racks on the underside ; suitable gearing is connected to these 

 racks, to give the table a slow alternate lateral motion so as to bring 

 every part of the plate of glass under the action of the rubbers. The 

 plates of glass are fixed upon the table by plaster of Paris, and the ends 

 of the table move between side blocks secured to the main frame, so 

 as to prevent the action of the rubbers from displacing it. The rubber 

 blocks are pieces of wood covered with felt, and provided with a central 

 spindle and adjustable weights to regulate the amount of friction ; a 

 number of these blocks are secured to two movable bars running on 

 rollers at each end of the table, and driven by a short shaft with cranks 

 at the ends set at right angles to each other. The rubber blocks are 

 thus worked transversely to the motion of the table ; and by applying 

 the polishing powder in a liquid state, the surface of the glass is gra- 

 dually brought up to the requisite degree of polish, both sides of the 

 plate successively being subjected to the same operation. 



About 1857 experiments were commenced at the British Plate Glass 

 Works, at Eavenhead, with an entirely different class of machinery for 

 grinding and smoothing plate glass, with the object of increasing the 

 production, reducing the cost, and also completing the process of 

 smoothing upon the same machine on which the glass is ground, so as 

 to obviate the necessity of a separate machine for smoothing, and also 

 save the expense and loss of time in removing and refixing the plates of 

 glass. The new grinding and smoothing machine consists of a revolving 

 table 20 ft. diameter, fixed upon a strong cast-iron spindle, and running 

 at an average speed of twenty-five revolutions per minute, driven through 

 an intermediate upright shaft from the main line of shafting by a pair 

 of bevel wheels, and friction cone for throwing in and out of gear. This 

 arrangement of gearing for driving the table was made by Mr. Daglish, 

 and was adopted in order to obtain a long spindle for the table, of a 

 length equal to the semi-diameter of the table, and at the same time to 



