For the information of the uninitiated it might be explained that in the macerating and intermediate machines the cog-wheels driving the two rolls are of different sizes (_i.e._, differentially geared), as opposed to the smooth rolls on which the cog-wheels are usually of the same size (_i.e._, even speed). The idea in the one case is to exert a "working" influence upon the rubber while it is being washed by the stream of water coming from above; in the smooth rolls a squeezing action only is effected. To give an idea of the ratio of the speeds of the rolls in each machine in a typical working battery, the following particulars may be noted: GEAR RATIOS.-- _Machine._ _Differential Ratio._ 1. Macerator 32-17 2. Intermediate (coarse grooved) 32-17 3. " (fine grooved) 30-19 4. Smooth (uneven speed) 30-19 5. " (finishing) 25-24 6. " ( " ) 25-24 It will be seen that the so-called "even-speed" smooth rolls run at approximately the same rate. It is advised that in all cases the gear wheels should be cut helically. Those who have experience of the noise of some batteries after they are slightly worn will appreciate such a remark. GROOVING OF ROLLS.--Concerning the choice of grooving, there is divergence of opinion, some managers preferring one type, which others reject in favour of another type. Provided any particular type can be shown to be as effective as required, no necessity for laying down hard-and-fast rules seems to exist. The following particulars serve to describe a battery well known to the writers, and accustomed to produce the finest quality of thin pale crepe and lower grades: -----------------+-----------------------------------+------------- | |_No. of Times _Machine._ | _Grooving._ |Rubber passes | | through._ -----------------+-----------------------------------+------------- 1. Macerator | Deep horizontal grooves; | | square-cut, 5/16 inch × 5/16 inch | | × 5/8 inch spaces | 3 2. Intermediate | Horizontal grooves; 3/16 inch | | × 3/16 inch × 3/8 inch spaces | 2 3. " | Fine spiral grooves; 1/8 inch | | × 1/8 inch × 1/4 inch spaces | 2 4. Geared smooth | Nil | 1 5. "Even" smooth | " | 1 6. " " | " | 1 -----------------+-----------------------------------+------------- | Total | 10 times -----------------+-----------------------------------+-------------