There are two other methods adopted in tapping, which are chiefly conflned to the Upper Amazon and its tributaries. Both are exactly on the same principle, the materials used being only a little different. The loose outside bark of the tree is cleaned off to a height of about 3 ft. Beneath, a gutter or raised border of clay is pasted or luted to the trunk, enclosing one-laalf or the entire circumference. Cuts are thickly made in the bark above this, from which, the milk flows down to the gutter, whence it is conveyed to fall into a calabash conveniently placed. The other naode is by winding round the trunk the stout flexible stem of a climber, and claying it round securely so that no milk may escape between the trunk and the climber. These plans are not extensively adopted, and can only be successfully put in practice where the trees have not been previously tapped. There is always a great deal of " negrohead," the result of the distance the milk has to run, and of the large quantity of clay employed in the process. The respective methods are illustrated in Figs. 1175, 1176, 1177. Fig. 1178 shows the exhausted tree in a state of decay.
Going from tree to tree, the collector empties the contents of the cups into a large calabash, which he carries in his band. As he pours the milk out of each cup, he draws his thumb or forefinger over tbe bottom to clean out some which otherwise would adhere. Indeed, a small quantity does remain, which is afterwards pulled off, and classed as sernamby. The cups, on being emptied, are laid in a little heap at the base of each tree, to be ready for the following morning. The trees occur at various distances (10-100 yd.) apart, and it is surprising that the natives have not yet seen the advantages that would be derived from forming plantations, whereby more than twice the quantity of rubber might be colleeted in one-fourth the time, and at far less cost and labour.
The common method of preparing the rubber is represented in Fig. 1179. The jars a are 18 in. high, and the bottoms are broken out. At the base, they are 7 in. diam., bulging out in the middle to 12 in., and narrowed at the mouth to a breadth of 2 in. Where a number of men are collecting for one master, much larger jars are in nee. The milk, on being put into a large flat earthen vessel b, is placed on the floor in a convenient position. Adjacent thereto, the jar is set on three small stones, which raise it to in. above the floor. The narrow space between the base of the jar and the floor allows the entry of air, which causes a current of smoke to ascend with remarkable regularity and force. When the fire commences to burn strongly, several handfuls of nuts (preferably tsrucuri [Altalea excelsa], but failing them, those of Euterpe edulis and other palms), are put on, thcn some more wood and nuts alternately. The latter are dropped in at the mouth of the jar, until it is filled to within 4 in. of the top. Due care is taken that a sufficient proportion of wood is put in with the nuts. The mould c on which the rubber is prepared resembles the paddle
of a canoe ; in fact, at many places on the Amazon, this is the article most frequently used, if there is niuch milk, and the rubber is prepared in bulky masses. Occasionally the mould is slung to the roof, as tho weight in handling it during the process would otherwise be very fatigning. A little soft clay is rubbed over it to prevent the rubber from adhering, and it is afterwards well warmed in the smoke. The oper ator holds the mould with one hand, while with the other he takes a small cup and pours two or three eups of milk over it. Ile turns it on edgo for a few moments above tho dish, until the drops fall, then quickly places thc fiat side 2 in. above the jar mouth, and moves it swiftly round, f1.8 if describing the form of a cipher, with his hand, so that the current of smoke may be equally distri buted. The opposite side of the mould is treated in the same way. The coating of milk on the mould, on being held over the smoke, immediately assumes a yellowish tinge, and although it appears to be fum on being touched, is yet fonnd to be soft and juicy, like newly-eurdled cheese, and to be sweating water profusely. When layer after layer has been repeated, and the mass ("biscuit") is of sufficient thickness, it is laid down on a board to solidify ; in the morning, it is eut open along the edge on one side, and the mould is taken out.
" Biscuit" rubber, when fresh, is often 4-5 in. thick. On being hung up to dry for a few days, it is sent to market. The rapid coagulation of the milk seems to be simply produced by the high temperature (about 180° F.) of the smoke. Cross thinks that with a strong current of heated air, or a good pressure of steam from a pipe, or by putting the milk in shallow vessels, and evaporating the moisture by the heat of boiling water, a similar result would be obtained. The finely divided particles of soot which form a large proportion of the smoke undoubtedly absorb a considerable amount of moisture, although at the same time forming an impurity.
A more modern method of preparing the milk is by treatment with an aqueous solution of alum, and subjecting the coagulated mass to pressure, iu accordance with Strauss' proposition. This plan is said to be in favour, as being capable of performance at a distance from the unhealthy locality where the milk is produced. The proportion of alum solution required is very small, but varies with the character of the milk. The latter should be previously strained free from extraneous matters. Coagulation ensues in 2-3 minutes. The rubber is then exposed to the air on sticks, and allowed to drain for 8 days. It is sometimes subjected to expression. The drawback of the process is the " wetness" wbich the rubber acquires from the presence of saline particles, which are never completely removed by pressing.