MA LTORE, 
[| NOVEMBER 8, 1906 
LETTERS TO THE EDITOR. 
{The Editor does not hold himself responsible for opinions 
expressed by his correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejected 
manuscripts intended for this oy any other part of NATURE. 
No notice is taken of anonymous communications.] 
The Extirpation of the’Tsetse-fly: a Correction and a 
Suggestion. 
Ix my letter published in Nature of October 25 on 
the breeding haunts of the tsetse-fly discovered by Dr. 
Bagshawe, I stated that there were no banana plantations 
on the deserted island of Kimmi, on the Victoria 
Nyanza, and suggested that the flies there must have some 
other breeding-places than the plantations. I am informed, 
however, by my friend and colleague Lieut. A. C. H. 
Gray, R.A.M.C., who has just started for Uganda, that 
he and the late Lieut. F. M. G. Tulloch, when collecting 
flies on Kimmi, came across deserted banana plantations, 
overgrown by the forest and bearing ripe bananas (a sure 
sign that no natives visit them or know of them). I must 
correct, therefore, my former statement. 
If the banana plantations should prove to be the sole 
or principal breeding-place of the tsetse-fly, the question 
at once arises, what means could be taken to exterminate 
the fly or check its increase? To destroy the plantations 
would be impossible, as I have said, because the banana 
is the staple food of the country. I venture to suggest that 
an efficient means of keeping down the tsetse-fly would be 
to encourage or constrain the natives to keep fowls in 
their plantations in places where the fly is abundant. 
These birds would scratch up and. discover the pupz much 
quicker than a man could, and would probably devour 
them greedily when found. In forest districts it might be 
seriously considered whether it would not be advisable to 
introduce the Indian jungle-fowl for the same purpose. It 
is, of course, always a risky thing to introduce exotic 
wild species into a country, but the jungle-fowl, being a 
valuable game-bird, could hardly be a serious nuisance, 
however much it multiplied. 
I would suggest, further, that a most suitable place in 
which to try experiments on the extirpation of the fly 
would be the island of Kimmi already mentioned. Within 
easy reach of Entebbe, uninhabited, covered with forest 
or jungle, and swarming with tsetse-flies, it is a locality 
in which it would be very easy to introduce the jungle- 
fowl and to watch the effects. As there are no monkeys, 
so far as I am aware, on the island, the fowl would prob- 
ably be able to flourish and multiply unchecked. Such an 
experiment, even if it failed to produce the desired effect, 
could do no harm, and if it succeeded would be of very 
great importance. E.. A. MINcHIN. 
Lister Institute of Preventive Medicine, November 2. 
The Efficiency of the Present Process of Natural Indigo 
Manufacture. 
In Nature of September 20 (vol. Ixxiv., p- 526) I find 
mention of a paper read before Section B at the recent 
meeting of the British Association by Mr. W. Popplewell 
Bloxam, on a new method of determining indigotin. It 
is stated that “‘ the author concludes that the present 
Process of manufacture is a wasteful one, the highest 
efficiency attained not reaching 50 per cent., whilst on the 
average only 25 per cent. of the indigotin in the leaves is 
extracted.’’ 
In justice to the indigo-planting community in India, I 
think this statement should not go unchallenged. The 
grounds on which Mr. Bloxam draws his conclusion are 
not given in the brief yéswmé of his paper in Nature, and 
I am therefore obliged to seek an explanation in his com- 
munication to the Journal of the Society of Chemical Indus- 
try of August 15 on the same subject, in which a similar 
statement of the low efficiency of the indigo-manufacturing 
Process is made. In this paper Mr. Bloxam gives the 
analysis obtained by his new method of the indigo turned 
out each day during the manufacturing season at a certain 
factory in Bihar. From the figure ‘so obtained, and the 
total daily outturn of finished indigo recorded in the factory 
NO. 1932, VOL 75] 
mahai”’’ book, he calculates the amount of indigotin 
produced day by day, and from the proportion existing 
between the, amount so calculated and the amount theo- 
retically obtainable, deduced from the weight of green 
plant placed in the vat and the assumption that this plant 
contaims 0-6 per cent. of indigotin, he arrives at his esti- 
mate of the efficiency of the manufacturing process. 
Now it is clear that in this method of calculation error 
may oecur in the following particulars :— 
(1) The analysis of the finished indigo. 
(2) Che weighment of the daily outturn of finished pro- 
duct. 
(3) The weighment of the green plant. 
(4) The assumed content of indigotin in the green plant. 
The first point is one for discussion elsewhere. It is 
sufficient for my present purpose to point out that the 
average of Mr. Bloxam’s results (60 per cent. indigotin) 
agrees substantially with the average quality usually 
accepted as typical of Bihar indigos, and that,. therefore, 
his results probably do not differ very widely from the 
truth. The same cannot be said of the second point. 
Separate weighment is hardly ever made of the daily out- 
turn of an indigo factory, and I know as a fact that this 
was not done in the case on which Mr. Bloxam bases his 
figures. A rough estimate of the outturn is arrived at by 
measurement of the cakes produced in a wet condition, 
and the result obtained generally falls short of the actual 
production by 10 per cent. to 30 per cent. Mr. Bloxam 
must therefore have obtained his figures from cake 
measurement—at best a very inaccurate proceeding. 
Similar inaccuracies occur in the weighment of the green 
plant in the ordinary factory routine; but the culminating 
error on which Mr. Bloxam’s figures are based occurs in 
his assumption of 0-6 per cent. as the amount of indigotin 
occurring in the green plant. It has been my privilege 
to serve the indigo planters in Bihar in a scientific capacity 
for nearly five years. During this time I have carried out 
some hundreds of analyses of indigo plants of all varieties, 
ages, and sizes, and in only one or two cases has so high 
an indigotin content as Mr. Bloxam assumes is normal 
been recorded. These were in cases of the Java plant 
(Ind. arrecta, which contains an exceptional amount of 
indigotin, and was only being cultivated on a small scale 
during the season from which Mr. Bloxam’s conclusions 
are drawn) under peculiar conditions of manuring. It 
would be more accurate to place the average indigotin 
content of the plant used during the season quoted by 
Mr. Bloxam at 0-3 per cent., so that his estimate of the 
efficiency of the manufacturing process should be doubled. 
As a matter of fact, recent work, carried out with atten- 
tion to the details I have enumerated, has shown that 
the process may with care, but with no modification other 
than is available to every planter, be rendered as efficient 
as 70 per cent. to 80 per cent., and that as it is carried 
out by the average planter it seldom falls below 60 per 
cent. C. BERGTHEIL. 
The Research Station, Sirsiah, Mozufferpore, India, 
October 10. 
The Leonid Meteors. 
TuHouGH the Leonid epoch of 1905 does not seem to have 
been marked by a great abundance of shooting stars, a 
magnificent aurora having unexpectedly taken the place 
on the evening of November 15 of the shower anticipated 
later on that night, yet it is probable that in the absence 
of moonlight and cloud the radiant in Leo would have 
been found to be more active than seemed to be the case. 
The phase of the moon renders the conditions for good 
observations more favourable in the present year, and it 
is probable that if the weather during the critical period 
turns out fine, Leonids will be observed in considerable 
numbers. In 1906 these meteors become due on the night 
of November 15. The anticipated display is connected by 
the nineteen-year period with the shower of November 14, 
1868, and, like the latter, will be visible over both Europe 
and America. As calculated by the writer, the principal 
maxima take place on November 15 at 12h. 45m., 14h., 
1gh., and 2th. gom., G.M.T. These maxima will there- 
fore occur on the morning of November 16, the first two 
being visible here, while the remaining two, which repre- 
