OLEORESIN PRODUCTION. 35 
Some of these are illustrated in Plate I, figures 3, 5, and 6, and Plate 
VII, figure 2. They present various advantages and disadvantages. 
The earthen or clay cups do not rust and discolor the gum as the 
metal cups that have been used for some time may do, but they 
are subject to breakage in handling and during freezing weather. 
Various efforts such as lining metal cups with wood have been made. 
One of the most successful has been coating old cups with bakelite, 
which prevents the discoloration of the gum. The argument that 
the metal cup becomes hotter during warm weather and causes greater 
evaporation of the gum is advanced by clay-cup advocates. Partly 
covered cups which reduce evaporation are used in India. 
The connection between the cup and the surface of the tree is made 
by the use of gutters or aprons. (PL I, figs. 3 and 6, and PI. IV, 
figs 1 and 3.) Efforts have also been made to develop an apronless 
cup. In order to attach the cups and gutters to the trees, nails are 
often employed, but these are very undesirable from the point of 
view of the sawmill end of the operation, for even though they are 
theoretically all removed, headless or hidden nails may occur and be 
very destructive if encountered during the process of sawing up the 
timber. With this in mind, wooden pegs (PI. IV, figs. 3, 4, and 
6) to support the cups or soft lead nails to attach the apron, when 
the cup is raised, are used by some operators so as to avert possible 
damage if accidentally left in the tree. 
CHIPPING. 
Two sizes of hacks are illustrated in Plate IV, figure 2. The hack 
with the narrow opening or "bill" is a "00," such as was used on 
the narrow chipping at Columbia, Miss. The other hack is a " No. 
2," such as was used on the standard operation by the cooperating 
company. The method of chipping, a free arm stroke, is illustrated 
in Plate IV, figure 4. It would be very desirable if a gauged hack 
could be devised which would mechanically govern the size of the 
chip cut. The " puller " for cutting a streak on the higher faces is 
illustrated in Plate IV, figure 6. It is said that " pulling " is more 
difficult than chipping 33 ; the use of the 00 hack and narrow chipping 
defers the time when pulling need be used. With the puller good 
narrow chipping may be obtained, as in the case of the double chip- 
ping at Columbia in 1917. It is thought to be highly desirable to 
use a sharp tool and to make clean smooth cuts at regular intervals. 3 * 
Practically, chipping once in seven days has been found to give 
satisfactory results. The Columbia, Miss., experiments indicated 
that chipping twice a week was not desirable for long operations. 
33 For. Serv. Bui. 90, p. 19. 
34 In India the smoothness of the face or channel is especially emphasized. The great- 
est care is taken to remove rough surfaces which would promote the formation of scrape. 
