510 
tulation by Mr. C. Bergtheil of the work done at this 
station during recent years, as well as an account 
of the work of the year under review, followed by 
an appendix of much interest by Mr. F. R. Parnell, 
reviewing the botanical work carried out at Sirsiah 
since October, 1909, for which he has been responsible. 
This work, it is explained, has been mainly devoted 
to the improvement of the plant grown, more especially 
in the direction of the selection of pure lines of the 
already cultivated plant possessing greater economic 
value than the ordinary mixed crop. This review of 
worls done will repay perusal, and the reader will 
recognise in it a modest record of good work faithfully 
and conscientiously performed. To those, however, 
who at a time when the natural indigo industry as a 
whole is being hardly pressed by the competition of the 
synthetic indigo-maker, find’ their sympathies still 
with the Behar planter, the text of this ultimate 
Sirsiah report will supply food for thought that is not 
altogether comforting. Of the two Indigoferas that 
are mainly grown in Behar—I. sumatrana, which 
displaced J. articulata about a century ago, and J. 
arvecta, the introduction of which is a matter of only 
a dozen years ago—a rather disquieting account is 
given. As to the former, there is a record of miser- 
able crops traceable, Mr. Bergtheil believes (p. 6), to 
the sowing of inferior seed; as to the latter there is 
a disheartening history by Mr. Parnell (p. 24) of 
‘‘disease,’’ which, so far, it has not been possible to 
attribute to fungal, insect, or bacterial attack, or to 
explain as the result of defective culture. 
In the Journal of the Franklin Institute (October, 
No. 4) appears an important paper by Mr. Frank K. 
Cameron, of the Bureau of Soils, U.S. Department of 
Agriculture, on kelp and other sources of potash. 
After briefly reviewing the fertiliser problems of the 
United States, Mr. Cameron gives an account, illus- 
trated by many photographs, of the movement recently 
started to utilise the giant “‘kelps” of the Pacific 
coast as a source of potash, which promises to develop 
into a very large and important industry. These 
giant kelps occur in numerous beds*or groves, often 
of a vast extent, and are characterised by an excep- 
tionally high content of potassium, five times on the 
average that of the better-known Atlantic alge. 
They are said to form ‘‘an ample, perennial possible 
source of potash for the present needs of the United 
States.”” Until recently the harvesting of the kelp on 
a sufficiently large scale to make it a commercial pos- 
sibility appeared the chief difficulty, but ingenious 
mechanical harvesters have been devised to overcome 
this. The costs of harvesting and utilisation are gone 
into in some detail, and it is pointed out that several 
soundly financed companies have already started 
operations on the large scale from which good results 
are anticipated. 
In an interesting article contributed to the Proceed- 
ings of the R. Academy of Amsterdam (vol. xv.) by 
Dr. C. Braak an attempt is made to show that by 
means of the connection perceptible between baro- 
metric pressure and rainfall in the Indian Archipelago 
it is possible to-make ‘‘a long-range weather forecast 
for the east monsoon in Java.’’ With respect to 
NO. 2305, VOL. 92| 
NATURE 
[JANUARY I, 1914 
deviations of air-pressure, the author states that Java 
has a special advantage, because the variations of 
climate there are determined by the variations of pres- 
sure in North Australia, the latter being characterised — 
by an extraordinary regularity. A barometric curve 
plotted for several years for Port Darwin shows some 
very regular series of waves, from which it appears 
that the time which elapses from minimum to maxi- 
mum is one year, from maximum to minimum two 
years, the period being exactly three years. These — 
regular periods are particularly adapted to forecast air- — 
pressure a considerable time in advance. On the 
principle upon which the scheme has been based it is_ 
claimed that it would have been possible to forecast 
the sign of the rainfall departure in Java for many 
of the years dealt with in the investigation. Attention 
is directed to the fact that in the Port Darwin curve 
the epoch of the maximum and minimum seems to be 
entirely controlled by the terrestrial seasons; cosmical 
influences, instead of causing barometric oscillations, 
seem to disturb them (namely during the sun-spot 
maximum). , 
Tue Journal of the Institution of Electrical 
Engineers for December 15 contains an extremely 
interesting paper by Mr. S. Evershed on the char- 
acteristics of insulation resistance. Mr. Evershed, as 
the result of a long course of experimental research, 
has come to the conclusion that the conductance — 
through insulators of the “absorbent” class, such as 
impregnated paper, fibre, or cloth, is entirely due to © 
the moisture which they contain. Curves are given 
to show that the insulation resistance falls as the 
voltage increases—or, as Mr. Evershed puts it, does 
not follow Ohm’s law. If, on the other hand, the F 
material is either perfectly dry or absolutely sodden — 
with moisture, the insulation is the same within wide 
limits of potential difference. Another interesting 
fact ascertained is that the conductance through an 
insulator containing a certain quantity of water is — 
far less than the conductance through the same quan- — 
tity and thickness of water. To account for this, Mr. 
Evershed puts forward the hypothesis, supported by 
an experimental ‘model,’’ that the moisture is dis- 
tributed unequally in the dielectric—that there are a 
number of ‘blind alleys,” and, in fact, only a very 
small proportion of the absorbed water is utilised in 
forming the leakage paths. In the discussion, Prof. 
A. Schwartz suggested that the distribution of the 
moisture in the dielectric followed a similar law to the 
distribution of sap in plants. 2 
“Let Us Have Our Calculus Early.” Such is the 
title of an article in the Bulletin of the American 
Mathematical ‘Society for October by Prof. E. B. 
Wilson, written professedly as a review of Mr. J. W. 
Mercer’s recent ‘‘Calculus for Beginners.” Writing 
of the great decline which has taken place in the 
sway of mathematics over collegiate education, Prof. 
Wilson points out that this has occurred at a time 
when the need of mathematical knowledge in all 
branches of science and technology is greater than it 
ever was in the past. ‘‘One of the main troubles 
with us is that we do not select the right subjects — 
to teach in the early collegiate years. There is no 
sense in giving the freshman a considerable course 
