December i, 1883.] 



THE TROPICAL AGRICULTURIST. 



449 



WHAT WE KNOW AND WHAT WE WANT 

 TO KNOW ABOUT GEAR A RUBBER. 



Sir, — We know a good deal about experiments on 

 a few individual trees, but we wunt to know some- 

 thing about results on a largei' aud more business like 

 scale. Mr. Gilliat is laet in tbe field, and gives us 

 interesting information, but, lilie his predecess irs who 

 who have written on rubber, he relates results of a few 

 trees only, and they do not add much to our previous 

 knowledge. 



We know that the tree will probably be short-lived. 

 So s.-vy botanists, and its very rapid growth favours 

 the idea.* If, theretore, we are to make any profit 

 out of it, we ought to begin at once to learn how 

 that is to be done. 



We know, that, whether the tree be young or old, 

 wounds made for the purpose of evtracting its milk 

 soon stop bleeding ; and then-fore a very little milk 

 can be obtained from any wound, however it may 

 have been made ; nor can we obtain much milk at 

 any one time, however many wounds we make. Trees 

 subjected to the severest treatment, in order to ascert- 

 ain the utmost yield of milk procurable, have proved, 

 by their insufficient yield, that we must depend for 

 any renumerative result on frequent tappings. We 

 know, in fact, that we must be content to tike a 

 little at a time, and to take it often. What we 

 want to know is how much we may take, and how 

 often. 



lu tbe fir.st place, therefore, we must devise a 

 method of tapping, which maybe often repeated without 

 material injury to the tree or the barlt. Every kind 

 of incisioa th.it has hitherto been tried, whetlier 

 vertical, horizontal , or arrowshajjed, has proved, 

 sooner or later, to seriously injure the bark. It is 

 true that the cuts or slits sometimes heal pretty 

 quickly, but they are often a long time in closing, 

 and produce serious scars. Some slits made several 

 months ago on trees a year old are gaping yet. Al- 

 though renewed baik has formed, it does not close 

 overthe wounds, which are now three times as wide 

 as when they were first made, owing to tlie rapid 

 growth of the trees. Perhaps, Mr. Gilliat's method 

 may succeed better, but that remains to be seen. 

 Meantime, it is satisfactory to know that a row of 

 punctures will yield as much milk as a vertical slit 

 or incision of the same length, whether such incision 

 be made down to the cambmra or be a mere shaving 

 down to the lacteals. Punctures heal quickly, witliout 

 material injury to tree or baik, and may be repeated 

 at vtry short intervals. Trees have been thus tapped 

 daili/ for several weeks without their showing any 

 difference as compared with untapped trees in adjacent 

 lines. Even when incisions heal completely, the re- 

 ne-ved bark, especially in old trees, is very rough aud 

 intractable. For sometime it yields very little nnlk, 

 as compiired with original bark, aud is .always rough 

 and uneven. The methods of tapping liy incisions 

 seem, therefore, to be a needless as well as an injuri- 

 ous mutilation of the trees. 



Jiy first prickers were intended to tear the bark 

 a little, in order to produce a wound that would not 

 close too quickly, but that is a mistake. A lOUgh wound 

 bleeds no longer than a smooth one ; aud a deep one, 

 down to the cambium, yields no more milk than a 

 shall 'wer one that reaches the lacteals. Tiie prickers 

 are now being made with a guard to prevent the 

 spurs going too deep, and are made to produce a 

 clean wound instead of a rough. 



The quantity of milk ijrocurable from different trees 

 of the same age, at the same day and hour, and from 



* The great longevity in the face of rapid growth of the 

 500 feet high eucalypti at Fernshaw in Victoria is the excep- 

 tion to the rule. — Ed. 



the same tree on different days, varies very much 

 This has been ascertained, but we ought to know the 

 cause or causes of this variation, so as to adapt our 

 proceeding accordingly. The factors of the variation 

 are probably the hour of the day, the state of the 

 weather, tbe condition of the tree, whether in flower, 

 fruit, or tiush, and the time of the year. The part 

 which each of tliese factors plays remnius to be as- 

 certained, and can only be found by persevering aud 

 systematic experiment. Occasional or casual trials are 

 of no avail whatever for this purpose. The milk 

 drawn in the eirly morning is generally thin aud 

 watery, and becomes thiclier as the day advances. 

 After 10 o'clock, it sometimes becomes too visv;id, but 

 in the evening it again flows more freely. As a rule, 

 milk may be drav.'n at all hours of the day, but it 

 remains to be seen whether it would be better to 

 discontinue the extraction during the heat of the day. 

 The quantity of milk drawn, so far as it depends on 

 the operator, is regulated, of course, by the length 

 of the vertii.al row of punctures. Hitherto, a double 

 row of 4 to 5 feet in length, on one side of a tree 

 of about 5 inches in diameter, has been found to 

 yield about 15 grains of dry rubber per tree. The 

 daily collection of a cooly is about half a pound, and 

 will probably be increased by improved appliances and 

 with larger trees. We want to know more about this ; 

 but, should it be found that trees will bear such 

 extraction for 240 days in the year, the cultivation 

 would be profitable, and tliere is reason to hope for 

 such a result. 



The curing of rubber seems to be a tedious busi- 

 ness. My lirst collections were made in tins and each 

 day's collection formed a cake at the bottom of tne 

 tin. 'Ihe milk coagulates so quickly that the cake, 

 though soft, can be removed from ihe tin when the 

 cooly returns from the field, but afterward.s it drits 

 and hardens slowly. Pressure causes a quantity of 

 liquid to exude, and even wheu the cakes are hard 

 they contain holes, like those in Parmesan cheese, full 

 of liquid. Late experiments have been made with 

 an a]>paiatus which torms the rubber into strings, 

 and these, when wound into a ball, look very pure 

 and business-like, but even these balls, when cut in 

 two, disclose some slight remains of liquid impurity. 

 Probably Mr. Christy's suggestion of the use of a 

 oheap i-pirit mighf assist in eliminating this mucil- 

 aginous matter; but spirit is co.stly, and there does 

 not seem to be much room for extra expenditure in 

 the process. The cake rubber was valued at '2s 6d 

 per lb. and the balls I think at 4s. 



The foregoing is very imperfect, aud shows rather 

 what we want to know than wliat we have already 

 learnt. Still, it is as far as*. I have got, and perhaps 

 some of your correspondents can advance in a step 

 or two further ? W. 



[It must not be forgotten that most of the experi- 

 ments yet made in Ceylon have been made on im- 

 mature trees. As the trees grow older, it seems 

 reasonable to expect if not more juice from a certain 

 surface yet a juice far less watery — almost pure gum, 

 in fact.— Ed.] 



THE EDINBURGH INTERNATIONAL FORESTRY 

 EXHIBITION. 

 Dear Sir.s, — t have jileasure in forwarding you the 

 enclosed list of patrons and prospectus of the "Inter- 

 national Forestry Exhibition " that is to be held 

 in Edinburgh next year. I am busy collecting, and 

 intend fori>ardiug as complete a list of Ceylon forest 

 produce as I can (lossibly gather together. I shall 

 arrange a catalogue of all the exhibits, which will 

 include a copy of your new Directory and Vincent's 

 report. Anyone willing to assist ine will receive 

 my best thanks. This proposed exhibition has been 



