276 
population, when, to avoid competition, the individuals 
at the periphery of the range of the particular species 
in distress are compelled to extend farther afield. But 
be this as it may, these lectures provide most stimulat- 
ing food for thought, and in their present form they 
have the further advantage of being most profusely 
illustrated. 
Tue failure of the North American wheat crop this | gests, however, that the methods of the industry have 
year is causing some anxiety in the West Indies, as 
the islands rely entirely on this source of supply. It 
seems doubtful if the usual quantities of flour will be 
available, and the question of possible substitutes is 
receiving official attention. The Agricultural News 
(Barbados) of October 21 suggests that the cultivation 
of maize, Guinea corn, cassava, and sweet potatoes 
should be extended. All these foodstuffs are already 
grown in the islands, but, in contrast with the im- 
ported cereals, none of them will keep without special 
precautions; the sweet potato, the principal vegetable 
of the people, is particularly perishable. As regards 
corn, the difficulty can be overcome by drying, and 
the Governments of Antigua and St. Vincent have 
established kiln driers working on a co-operative basis. 
If the shortage of wheat flour should become serious, 
the rice crop of British Guiana will have to be drawn 
on to a greater extent than it is already, and the 
cultivation of this cereal, which is at present a large 
industry in Trinidad, may be further developed. 
In view of the shortage of potash by reason of the 
cutting off of the supply from German sources, two 
papers recently issued by the United States Geological 
Survey are now of especial interest. The first, 
‘“Evaporation of Brine from Searles Lake, California” 
(Professional Paper 98-A), records experiments by Mr. 
W. B. Hicks designed to discover an economical 
‘method of extracting the potash from the brine of 
Searles Lake. The latter is a bed of crystalline salts, 
containing in its interstices a brine which carries about 
2-1 per cent. of potassium, probably in the form of 
chloride, sulphate, carbonate, and borate. The brine 
was fractionally evaporated and crystallised, the de- 
posits formed during evaporation being kept separate 
from those resulting on cooling. As a result of a 
series of seven such evaporations and crystallisations, 
the author shows that only 8 per cent. of the potassium 
in the brine is separated, during either the evapora- 
tion or the subsequent cooling, when this is concen- 
trated to one-half of its original volume. When the 
brine thus concentrated is further evaporated to about 
one-fifteenth of its original volume and cooled, more 
than 7o per cent. of the total potassium present is 
deposited, whilst 12-13 per cent. is left in solution. 
The second paper, entitled ‘‘Experiments on the Ex- 
traction of Potash from Wyomingite” (Professional 
Paper 98-D), is by Mr. Roger C. Wells! Wyomingite 
is a lava composed largely of the mineral: leucite, 
which is a silicate of alumina and potash. The sub- 
stance was subjected to levigation with water after 
crushing, was extracted with water in the presence 
of gypsum, was heated alone and with gypsum, 
sulphuric acid, potassium, hydrogen sulphate, alunite, 
calcium carbonate, calcium and magnesium chlorides, 
ammonium sulphate, and a bittern respectively. The 
results indicate that the most promising method would 
be to heat the wyomingite with so per cent. of its 
weight of alunite (a naturally occurring sulphate of 
alumina and potash found in the same neighbourhood 
as wyomingite), whereby 70 per cent. of the total 
potash (55 per cent. of that in the wyomingite) is 
rendered .soluble. z 
A GENERAL survey of the coke industry of, New 
South Wales is made by L. F. Harper and J. C. H. 
Minguye in Paper No. 23 of the New South Wales 
NO. 2458, VOL. 98] 
NATURE 
[DECEMBER 7, 1916 
Department of Mines and Mineral Resources. Chem- 
ical analyses and physical properties are given for all 
types of coal found in New South Wales, and also 
unusually complete analyses of the coal ashes. Coke 
burning has been established in the colony for half 
a century, and is an important and growing industry, 
the production having risen from 304,800 tons in 1914 
to 417,753 tons in 1915. A perusal of this report sug- 
not kept pace with modern coke-oven practice. Pre- 
liminary coal-washing is carried on to a very limited 
extent, although the ash content of the cokes is very 
high, and there is some laboratory evidence that wash- 
ing would be serviceable. The sulphur in the coals 
and cokes is quite remarkably low, and might be even 
lower after washing. Unfortunately the survey has 
not included nitrogen content. The coking properties 
of the coals are good. A modified beehive oven is 
most commonly used for coking, rectangular in plan, 
but with arched roof. The coke is discharged by a 
ram and quenched outside the ovens. Heating is 
effected by burning part of the cole-oven gas in ex- 
ternal flues, and in some plants the waste heat is 
collected for power production. The ordinary beehive 
oven is also in use, but only one modern by-product 
plant is in full operation (since 1915)—a battery of 
regenerative Semet-Solvay ovens at Newcastle, N.S.W., 
with semi-direct ammonia recovery and a benzol plant. 
Another battery of ovens of the Coppée type has been 
built in the neighbourhood, but trouble with refractory 
materials seems to have hindered its operation. Re- 
sults obtained in the recovery ovens suggest that 
coking for by-products should have good prospects; . 
the yields are stated as 30 lb. of ammonium sulphate, 
3 gals. of benzol, 8 gals. of tar, 12,600 cub. ft. of gas 
(585 B.T.U.) per ton of coal. It is believed that these 
results may give a practical object-lesson on the possi- 
bilities of by-product coking in the colony, and do 
something to destroy the prejudices and conservatism 
evidenced by the general use of older, simpler, and 
cruder types of plant. 
SciENTIFIC PaPER No. 294, issued by the U.S, Bureau 
of Standards, gives an account of the accurate re- 
determination of the freezing point of mercury made 
at the bureau by Mr. R. M. Wilhelm. Temperatures 
‘were measured by means of three platinum thermo- 
meters standardised at 0° C., 100° C., and 444-6° C. 
About 40 c.c. of mercury were placed in a glass tube 
of 2 cm. inside diameter, and into it the bulb and a 
considerable length of the stem of the platinum ther- 
mometer were inserted. The mercury tube was sur- 
rounded by another glass tube of 3 cm. inside dia- 
meter, which was placed in a well-stirred freezing 
bath. In making a determination the temperature 
of the bath was maintained either a little above or a 
little below the freezing point of the mercury, and 
the slow change of temperature of the mercury owing — 
to the transmission of heat across the layer of air 
between the two glass tubes was observed. At the 
melting- or freezing-point the temperature remained 
constant for ten to twenty minutes. Three different 
samples of mercury were used, and after purification 
gave identical results. The final result of the whole 
series of measurements is —38-873° C. 
_ Tue Journal of the Franklin Institute for Novem- 
ber contains an account of some interesting work on 
riveted joints by Mr. Cyril Batho, of the McGilf 
University. . By means of the principle of least work 
it is shown how a series of equations may be obtained 
for any riveted joint, giving the loads carried by each 
of the rivets in terms of a quantity K, which depends 
upon the manner in which work is stored in, or by 
the action of, the rivets. A large number of experi- 
ments have been made with the object of determining 
