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OSs ee Sc el e”t—— 
DECEMBER 7, 1916] 
Luminous Gentipedes. 
WitH reference to the paragraph in Nature of 
November 23 (p. 233) on luminous centipedes in 
France, it may be of interest if I mention that these 
were very frequent in the neighbourhood of Albert 
and Fricourt in the autumn and winter months a year 
ago. They appeared to be Geophilus electricus, which 
I had often seen glowing, particularly on mild, damp 
evenings in late autumn, in Surrey lanes, and some- 
times on garden paths in London suburbs. 
As the troops marched across the damp grassland 
to and from the trenches by night, the spots of phos- 
phorescence on the ground at their feet were taken for 
glowing match-ends, though one might occasionally 
hear a man from tke country refer to them as ‘ glow- 
worms,’”’ JT have more than once known an officer 
get seriously perturbed when troops were marching 
across a ‘danger zone and the glowing points on the 
ground seemed evidence that the men were disobeying 
the “‘no smoking” order which had been passed along 
the column! 
Luminous centipedes were also to be found in the 
trenches themselves. (Sergt.) F. M. Roserts.., 
Sutherlands Auxiliary Hospital, Reading, 
November 27. 
Searchlights. 
SEARCHLIGHTS are now so common that it may be of 
interest to record that, as might have been expected, 
the beam shows the presence of polarisation, if it is 
viewed through a Nicol prism, the line of sight through 
the prism being perpendicular to the direction of the 
beam. On rotating the prism, the part of the beam 
viewed changes its intensity in such a way as to show 
that the light reflected from it is polarised in a plane 
passing through the length of the beam and the eye 
of the observer. The best results occur, of course, 
when the haze reflecting the beam is thin in char- 
acter, its particles being small.’ In such cases the 
a nearly disappears for a suitable azimuth of the 
Nicol. C. T. WuitMett. 
Invermay, Hyde Park, Leeds, December 1. 
Columnar Ice-Crystals. 
AFTER the recent frost a thin layer of gravel became 
separated from the rest on the paths here (in the park) 
and on examination was found to be supported by 
columnar ice-crystals resembling basalt or sal-ammo- 
hiac in formation, ’ 
The columns were vertical and parallel, closely 
packed lead and of uniform length (about one 
centimetre). ‘ 
I should be glad if some reader would kindly explain 
this (to me) remarkable uniformity. 
A. E. Larkman. 
County School, Merthyr. 
AGRICULTURE AND THE WHEAT SUPPLY. 
Maas present high price of food has directed 
attention to the urgent need for increasing 
the production of wheat in this country so that 
we may be less dependent than at present on 
foreign supplies. Prior to the outbreak of war 
the official ‘statistics showed that we were pro- 
_ ducing only about one-fifth of the wheat we con- 
sumed. As the war came in August our home- 
grown supply was at its maximum, and the Board 
of Agriculture was able to issue a reassuring report 
as to the quantities in hand. But the shortage of 
NO. 2458, VOL. 98] 
| of what cultivation does to the soil. 
NATURE ay 269 
available shipping has so affected the amounts of 
imported wheat that the demand has exceeded the 
supply, and in conséquence prices have risen. 
The production of wheat on a large scale in 
this country is by no means a simple matter. 
There are, broadly speaking, three factors, soil 
and climate, economic conditions, and labour, each 
of which has to be considered separately. 
The most fundamental way of increasing the. 
amount of wheat is to increase the yield per acre, 
and this can be done by either (a) improving the 
soil conditions, or (b) introducing new varieties 
capable of better growth than those already in 
use. 
The improvement of soil conditions is. brought 
about by increasing the supply of plant nutrients, 
i.e. artificial fertilisers, by cultivation, and in other 
ways. Before the war the world’s consumption of 
artificial fertilisers was increasing more rapidly 
than the supply, so that prices were going up;. this 
was particularly true of nitrogenous fertilisers. 
During the war farmers haye had a demonstration 
of the value of artificial fertilisers, which. will 
probably lead to a larger consumption after. the 
war. The whole trend, of the activities of the 
educational and advisory staffs of the agricultural 
colleges and other institutions is in this direction.* 
The newer agriculture in other countries also calls 
for more fertilisers: Japan, Australia, India, 
Africa, and Java are all importers of artificial 
fertilisers from Europe. It seems reasonable to 
anticipate, therefore, a considerable increase: in 
the consumption of these fertilisers provided the 
supply is forthcoming, and one of the most im- 
portant and most hopeful problems for the future 
is to ensure these supplies. 
Better cultivation of the land requires better 
implements, but, above all, a better understanding 
Research in 
this direction is in hand at Rothamsted and else- 
where, but considerably more work is wanted on 
the study of implements and better opportunities 
for testing them. 
The production of new varieties is another 
method by which yields may be increased. Soil 
and climatic conditions are capable of only a 
certain degree of modification, and it is clearly an 
advantage when the plant-breeder can meet the 
soil-improver half-way and produce a new plant 
better adapted than the old ones to the conditions 
actually obtaining. The work of the newer school 
of botanists seems full of promise in this direction; 
Prof. Biffen at Cambridge has already done a good 
deal, and the move of the Botanical Section of the’ 
British Association in appointing a special com- 
mittee to consider this matter is a welcome sign of 
their intention to attack an important and highly 
interesting problem. 
Another method for increasing the amount of 
home-grown wheat is to increase the area devoted 
to wheat either by taking in'’more land or by dis- 
placing some other crop already grown. Incteas- 
ing the ‘area of land is a favourite suggestion, 
but one fraught with numerous difficulties: The 
non-technical tourist walking over Dartmoor or 
