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THE TROPICAL AGRICULTURIST. [January 2, 1882. 
" NEW PRODUCTS" : — CHANGE IN THE 
MODE OF TANNING LEATHER. 
London E.C., 24th Oct. 1881. 
Sir, — So many of yonr subscribers ask me to keep 
them informed of the natural products which are likely 
to turn to a profitable account, that I think I cannot 
do better thau to give you the opportunity of pub- 
lishing a change that is sure to take place in the 
mode of tanning leather in this and other countries. 
It is known to most of your readers that the old 
process has been to place the hides in pits, and, 
after the hair has been taken off by lime, purge 
out the lime by glucose : they are then placed in 
pits and exposed to the action of bark, the tanning 
of which is extracted generally by cold water. To 
obtain perfectly tanned butts, it has been thought 
necessary to wait twelve months for the tannin to 
enter the hide. 
The Americans have shewn that by using extracts, 
prepared with hot water and carefully sent to this 
country in casks, the process has been greatly ac- 
celerated. Other compounds have been found which 
assist in turning out the leather rapidly, and tanning 
it effectually and .sufficiently. Some of the advanced 
tanners now go so far as to say : " We admit the 
great difficulty there is in collecting and drying the 
bark of trees, also the costliness of the freight, owing 
to the unsatisfactory nature of the packages, and, 
at the same time, we admit that we can with much 
greater effect empky extracts." 
Since they have had the small " tannometer " or 
" tann-tester," which only costs ££ complete with 
glasses and test tubes, they are enabled to gauge 
exactly the value in tanning matter of anything that 
they may use, or that may be offered to them, and 
it is only this week that I have had sent me, by 
one of the most advanced tanners who thoroughly 
Understands chemistry, two barks, which are said to 
come from India, which yield 15 per cent of tanning. 
The extract from this wood can be easily made on 
the spot, and shipped home in casks, or cases. 
One is "Acacia Arabica" babao bark; the other 
material we have not yet found out the name of 
for certain, but it is one of the varieties of the 
"mimosa." 
Another great point gained is that, in India, ex- 
tracts are so easily made in large pans, and the sun 
so helps in evaporating the last portion of the moist- 
ure, so that extracts actually come from hot climates 
in better order than they can be prepared in the cold 
damp climates. In South America, where there is a 
large quantity of fine tanning material, such as the 
red Quebracho ( 'Quebracho Colorado"), they can 
make the extracts, bu' ; they are not so well off for 
coopers to turn out the casks at a low price ; but 
there is room for all. I need hardly add that I shall 
be delighted to render your subscribers any further 
information in my power, and also put them in the 
way of testing the value of the trees and plants 
that may be growing around them. — Yours truly, 
THOS. CHRISTY. 
[The Government of India have published numerous 
and elaborate reports on tanning barks, but there is 
r oom for further experiments in (he direction of pre- 
paring extracts. — Ed.] 
POTASH VERSUS SUPERPHOSPHATE OF 
LIME AS MANURE FOR COFFEE. 
32, Great St. Helens, London, 28th Oct. 1881. 
Deak Sib, — It is a long time since I inflicted a 
letter on you, and I will not allow another number of the 
Tropical Agriculturist to reach me, without compliment- 
ing you on the idea and its execution. I observed in 
No. 1 that Mr. Hughes had fired a parting shot at me, 
to which I turned my other cheek, having passed 
the age when an accusation of wasting anything is 
likely to apply. In this case, the expression "expensive 
fertilisers of an exceedingly soluble nature" is singularly 
infelicitous, since the mixture I use costs just about 
half as much as that recommended by himself, and 
should be worth about one-third more according to the 
valuation. So much for the expense. Now for the 
solubility^: I do not use superphosphate at all, because, 
unless I am very much misinformed, it is too soluble 
for soils containing a large proportion of iron, which 
has a greater affinity for it and turns it into phosphate 
of iron instead of phosphate of lime. Moreover, the 
Aberdeenshire experiments shew that a finely ground 
bone-dust or natural phosphate is for us coffee plant- 
ers quite as soluble (practically speaking) as super- 
phosphate, and much more lasting. I maintain my 
opinion as to the necessity of a larger proportion of 
potash thau Mr. Hughes recommends, and I have 
another year's results to confirm it. Before entering 
upon them, however, I will mention that, conversing 
with Mr. Dyer some time ago on the subject of potash, 
he remarked that most probably our soils had a 
much gn-ater affinity for it than was generally supposed, 
from the heavy rainfall they had to endure. He said 
he would test the idea, and afterwards most kindly 
sent me the results in an interesting paper, too long to 
give in extenso. I may summarize them as follows : — 
The soil experimented on contained 
Oxide of iron about... ... 10'7 
Alumina ,, ... ... 10 7 
Potash ,, ... ... -275 
Two columns of soil 16 inches deep had a top-dress- 
ing of muriate of potash = 2j tons per acre (of course 
an excessive dose); 31 inches of rainfall percolated 
through the soil without potash extracted — '0029 or 
about 1 -100th of the natural potash. The same water 
extracted only l-12th of the added pocasb, so that 
ll-12ths were fixed by the soil. With nitrate of potash 
(saltpeter) 81 inches water removed 1- 10th and a fur- 
ther 81 inches 2- 10th ; so that 162 inches rainfall 
removed less than 3-10ths— which does not look like 
" exceeding solubility." 
1 have steadily persevered in the same plan for the 
last 3 years, and have but one uniform report of 
marked improvement in results. In Wynaad a new 
head-superintendent, a gentleman fresh from Ceylon, 
appears astonished to fiud estates so free from leaf- 
disease and with a good crop on them. From two or 
three Ceylon friends who have followed my advice, 
and from Coorg, Mysore, and the Neilgherries, I have 
the same encouraging results, and by the last mail 
only I learned something I have been anxious to know. 
On estates poor in phosphates but rich in potash, I 
applied bone-dust alone, and the mixed manure. The 
superintendent reports: — "There seems to be little 
difference between the parts manured with bone-dust 
and those done with the mixture, so far as leaf is 
concerned, but crop is heavier where the latter mau- 
ure was applied. " An estatu I mentioned in a previ- 
ous letter as richer in potash than any I had beard 
of ("418) where I intended trying the mixture, not- 
withstanding Mr. Hughes' objections, gives the same 
result, and the report is : — " The half of the northern 
bank done with the mixture, when I took charge in 
April 880, has a splendid crop and abundance of new 
wood." The previous year it did not pay expenses; 
in fact, had, I believe, never been manured at all. 
I write this mainly because I have many friends 
interested in Ceylon, and I observe there a sort of 
reckless rushing after every quack of whatever nation- 
ality who rattles off a lot of glib nonsense, and after 
any product you can mention except the good old 
staple coffee, which I believe and have found, only 
