6 NORTH SHORE BREEZE and Reminder 
xcellence. Here the delighted visitor may well linger 
over the dainty bits to be found as well as specialties only 
to be bought in Salem. And as the day wears on, the 
convenient little tea houses, here and there on the main 
street, furnish refreshment for the busy sightseer and 
shopper. 
So at the end of the visitor’s stay in Salem it will be 
August 13, 1915. 
duly impressed on his and her mind that Salem is not 
only a place of historic value, but it is a center to wnica 
it is well worth while to come for trading purposes. And 
Salem, the center of half a million population, was never 
better able to care for the vast influx of trade that is now 
coming to her doors, and bids fair to increase more and 
more as time wears on. 
Explosives—Their Use and Production 
Discussed by MAJ. 
HILE several million pounds of powder are being 
burned weekly on the battle fields of Europe, and 
discussion is rife on the’ American manufacture of the 
same, an article on explosives just issued by the Smith- 
sonian Institution gives much timely information on the 
subject. 
The paper is written by Maj. Edward P. O’Hern, 
of the ordnance Department, U.S. Army, and deals with 
the importance of the so-called explosives and the pa 
creasing extent of their use and production, as weil a 
their composition, uses, method of employment, and he 
results accomplished. 
“An explosive,” says Maj. O’Hern, “is a substance 
of which the molecules are made up of a number of atoais 
or units rather loosely bound together in an unstable con- 
dition, ready to seek new and simpler combinations upon 
the furnishing of a sufficient motive force to start the 
operation. ‘This is usually supplied through a_ primer 
ignited by a slow-burning fuse, or by a wire heated by 
an electric current. When started, the leat and shock 
developed will cause a continuation of the action through- 
out the mass-of the explosive. The enormous power that 
can thus be developed from a co-vparatively small quanity 
of material is indicated by the thousands of fragments 
into which a 12-inch armor-piercing projectile was broken 
by the detonation of a bursting charge about 5% percent 
of its weight.” 
The author divides explosives into three classes, pro- 
gressive or propelling explosives, known as low explo- 
ives; detonating explosives, or high explosives; and 
detonators or fulminates. For all classes the effect of 
the explosion is dependent upon the quanitity of gas and 
heat developed per unit of weight and volume of the ex- 
plosive, the rapidity of the reaction, and the character of 
the confinement, if any, given the explosive charge. The 
rapidity of reaction varies greatly with different ex- 
plosive substances and with the manner in which the ex- 
plosion is started. 
Black gunpowder, smokeless powder, and black blast- 
ing powders are known as low explosives, for certain of 
which, such as smokeless powder, the explosion does not 
differ in principle from the burning of a piece of wood or 
other combustible. ‘The combustion is very rapid, but is 
a surface action proceeding from layer to layer until the 
grain is consumed. Such materials are known as low 
or progressive explosives, although the total power devel- 
oped through the combustion of a unit weight may be 
very great and would be destructive unless properly con- 
trolled. 
In high explosives such as dynamite, nitroglycerin, 
guncotton, some blasting powders, and most of the “per- 
missible explosives” approved by the U. S. Bureau of 
Mines for use in mines where gas explosions are liable 
to occur, the progress of the explosive reaction is not by 
burning from layer to layer, but the breaking up of the 
initial molecules gives rise to an explosive wave which 1: 
O’HERN, U. S. A. 
- 
transmitted with great velocity in all directions through- 
out the mass and causes its almost instantanecus con- 
version into gas. The velocity of propagation of the 
detonating wave has been determined for some i) ateria's 
tc be more than 20,000 feet per second, or approxi ately 
four miles per second; this form of materia! is used in 
shells and for bursting purposes. ‘The progressive emis- 
sion of a gas from a low explosive such as burning gun- 
powder, produces a pushing effect upon a p: ojcctile, 
whereas the sudden conversion of an equal weight of ma- 
terial into gas, as would happen with a high explosive 
such as dyna:nite or nitroglycerin, would develop such 
high pressure and shattering effect as to rupture the gun. 
The action of fulminates is much more bruscue and 
powerful than that of the high explosives. Since they 
can be detonated by shock or the application of heat, they 
are used in primers and fuses to start action in both low 
and high explosives. One of the most ivportant ful- 
minates is fulminate of mercury, which produces a pres- 
sure of about 48,000 atmospheres. 
At no time in the history of the world have ex- 
plosives played such a mighty part in deciding the destiny 
of nations as they are playing today in the prosecution of — 
the general European war. ‘Their extensive use in the 
mighty engines of destruction such as the submarine mine, 
the torpedo, and in projectiles thrown from cannon to 
great distances with marvelous accuracy, is resulting ia 
loss of life and destruction of property on an unpre- 
cedented scale. 
Beginning with black powder, the earliest record of 
which in actual war was in the fourteenth century, the 
author follows the development of powder through its 
early stages of brown powder, to the two principal! forms 
of smokeless powder for military purposes, nitroce!ulose 
and nitroglycerin, stating that the use is quite eveniy 
divided; the U. S. Army and Navy, the French Army 
and Navy, and the German eli using the former, and 
the British Army and Navy and the German Navy using 
the latter. He then gives much detailed information con- 
cerning the manufacture, life, source of supply, and tests 
of smokeless powder manufactured from nitrocellulose 
or guncotton. Following which, subjects relating to life 
cf guns, bursting charges for projectiles, armor-piercing 
projectiles, high explosive shells, shrapnel, fuses, aero- 
plane bombs, means of igniting explosives, mines, tor- 
pedoes, and the storage and shipment of explosives in the 
United States are discussed. 
THe CHEERFUL Optimist. 
“T am so pained about my husband’s conduct.” 
“You poor dear! - What has he been doing?” 
“Every time he goes fishing he lies to me “about his 
eaten’ 
“You're a lucky woman. Why, if my husband never 
lied to me except when he went fishing I’d think I had a 
jewel.” 
