JuLy 29, 1915] 
increased by nearly 50 per cent., whilst the projectile 
is far heavier. 
Our enemies in the field are using guns, howitzers 
and mortars, the two latter classes being used for 
indirect fire from behind shelter, for which their high 
trajectory specially fits them, whilst the field artillery 
used by them are chiefly quick-firing 77-millimetre 
guns (3:03 in.). One of the new features they have 
introduced into the present warfare is the use of siege 
guns of much larger size, transported by motors, and 
so made available for field work, whilst amongst the 
other artillery in use are the celebrated Krupp siege 
howitzers of 16-8 in. calibre, but probably the most 
deadly innovation has been the almost unlimited use 
of machine guns, to the perfecting of which the Ger- 
mans have devoted many years, and of which they 
have an enormous supply. 
IJ.—SHELLS AND HIGH EXPLOSIVEs. 
The shells used in big guns and field artillery may 
be divided into two main classes: shrapnel, which is 
utilised against troops in the field, and is of but little 
use against fortifications or trenches, and high explo- 
sive shells, which may be either armour-piercing or 
ordinary. 
The shrapnel shell is a hollow cylindrical steel pro- 
jectile packed with bullets, at the base of which is a 
bursting charge that may be gunpowder or high ex- 
plosive, whilst in the nose of the shell is arranged 
the time fuse connected by a tube to the bursting 
charge, and so regulated that the shell can be exploded 
in the air at any desired point, the bullets and frag- 
ments of the shell being driven forward and spreading 
over a considerable area. The shrapnel used in the 
ordinary field gun is an 18-lb. projectile, containing 
375 bullets, and when burst at the right altitude is a 
most deadly weapon against troops, especially when 
in massed formation. Since its invention by the 
officer whose name it bears, shrapnel has been looked 
upon in the Service as the form of shell most necessary 
in field operations, and during the present war our 
supplies have been ample for all requirements. 
For fortified trench warfare, such as has been the 
characteristic feature of the fighting on the western 
front since September, shrapnel is not effective, as it 
does but little damage to earthworks, wire entangle- 
ments, and other defences, and this practically new 
phase of field warfare has to be met by the use of 
high-explosive shells, capable of detonating with such 
enormous concussive power as to destroy physical 
obstructions, crumble earthworks, clear wire entangle- 
ments, and reduce the defenders in the trenches to a 
dazed and stunned condition by the action of con- 
cussion on the heart and nerves. 
Under the conditions created in the present war both 
classes of shells are needed in the field—the shrapnel 
to resist infantry attack, the high-explosive shells to 
clear the ground and prepare the way for attack on 
the enemy, and it has been an insufficiency in the 
supply of the latter which has given rise to so much 
criticism, mostly undeserved and wholly unwise. At 
the present time obstacles to supply in all directions 
have been surmounted, and a steady and ever-increas- 
ing stream of shell is flowing to the front. 
The high-explosive shell is made of forged steel 
with comparatively thin walls and a heavy bursting 
charge, but the large naval shells and those for the 
siege guns, which have to penetrate heavy armour, 
are made from ingots of chrome or chrome-nickel 
steel, forged, hardened, and the nose capped with soft 
steel, which prevents the shell from shattering on im- 
pact with the hardened steel armour. These shells 
also contain a heavy charge of high explosive, gener- 
ally cast into the shell in a fused condition. 
NO. 2387, VOL. 95| 
NATURE 


607 

All these forms of shell are fitted with the usual 
soft copper driving bands near the base of the shells; 
these bands take the place of the projections used in 
the early forms of shell to fit the rifling of the gun. 
The copper band, under the pressure existing during 
the firing of the charge, is pressed into the grooves 
of the rifling in the gun, not only imparting rotation 
to the projectile, but also acting as a gas check to 
prevent the rush of the gas past the projectile, an 
action which had accentuated the serious erosion with 
Mark I cordite. 
For trench fighting the grenade has now again come 
into use, and the most modern forms are in reality 
miniature shrapnel shells, which are fitted on to a rod 
that can be fired from a rifle, or, where the trenches 
are close together, can be thrown or slung by hand. 
The body of the grenade is made of steel or malleable 
iron so serrated as to break up on explosion into many 
pieces; it contains a charge of T.N.T., and a tetryl 
detonator fired on impact by a needle liberated only 
after the grenade has travelled a certain distance, so 
as to render premature explosion impossible. The 
weight of such a grenade is about 23 oz., and when 
fired its range would be about 300 yards, but when 
hand-thrown not more than 4o or 50, and its flight 
through the air is steadied when fired by a rod, which 
for hand use is replaced by a rope tail. 
One of the things that strikes the ordinary observer 
most when considering the composition of the explo- 
sives of to-day is that they are all derived from sub- 
stances of the most commonplace and harmless de- 
scription, and probably the greatest mistake the 
Government has made in this war was in not making 
cotton contraband from the commencement, and it is 
inexcusable that the mistake should not be rectified. 
There is not the least doubt that Germany had 
enormous supplies of cotton at the commencement of 
the war, as well as huge quantities of manufactured 
explosive, but the factor which she had omitted to 
reckon on was the duration of the war, which was 
expected to be over last November. It has been calcu- 
lated that Germany and Austria need r1ooo tons of 
cotton.a day, and it has been proved that the neutral 
European countries—Holland, Denmark, Sweden, and 
Norway—imported during the first three months of 
this year six times the amount they did in the corre- 
sponding period of last year, and there can be but 
little doubt as to where this enormous surplus went. 
Directly there is any tallx of making cotton contra- 
band German articles appear in the Press of the 
neutral countries pointing out that it is not aimed at 
German explosives, but is England’s attempt to corner 
the trade in textile fabrics, but for some inscrutable 
reason the Government has so far declined to do the 
one thing that more than any other would shorten the 
war. 
We have seen that cotton and glycerin when nitrated 
and blended with vaseline yield cordite, which serves 
asa propellant in all our guns, whilst the high explo- 
sives used in shells, torpedo heads, mines, and 
aviators’ bombs are almost entirely derived from coal- 
tar derivatives by nitration. When coal tar is sub- 
jected to fractional distillation the portion which 
comes over up to a temperature of 170° C. is called 
‘light oil,” and contains all the compounds of low 
boiling point found in the tar, and, as we shall see, 
from this several of our most valuable explosives can 
be obtained. When these light oils have distilled over 
the next fraction or ‘‘middle oil” yields phenol or 
carbolic acid, a body which when nitrated gives picric 
acid, the basis of the French high-explosive melinite, 
the Japanese shimose powder, and the English lyddite. 
Picric acid is a nitro-substitution product, three 
atoms of the hydrogen of the original phenol being 
