can be the only one that can act, but
this will be too late, as the shell bursts
too late, whether it be a gunpowder or a
gun cotton shell."
From these constructions of Major
Schumann it appears that he expects im-
portant results from the use of sudden
explosives as a charge for armor shells,
and we add, in reference to the technical
construction, the following :
In case gun cotton, as a charge for ar-
mor shells, which therefore penetrate into
the armor, detonates directly from the
shock of the shell in striking the armor
plate, and this without fuse and without
primer — ^we do not doubt that the dry
priming cartridge will partially bum or
explode, the only question is, will it de-
tonate in such a way as to cause the wet
gun cotton to detonate at the same time ?
—then it will detonate before the shell
has exerted its full energy, hence too
soon. The development of the detona-
tion of gun cotton as compared to that
of gunpowder is, as we observed, instan-
taneous, and this will be true whether it
is caused by the primer or by the shock.
A fuse, even a slow one, in projectiles
which strike armor plate perpendicular-
ly and penetrate into it, will break, hence
no effect can be expected from delaying
the bursting by making the fuse a slow
one.
In case dry gun cotton is detonated by
the shock, the bursting of the shell will
take place too early ; in case it does not
detonate, but only takes lire and under-
goes partial combustion, it would be
possible — by arranging the primer in the
shell so that it is not detonated too early
by the shock in the bore of the gun and
cause bursting in the bore — ^to delay the
bursting of the shell, and the events tak-
ing place in the shell would succeed each
other as follows :
The primer would be detonated by the
burning dry gun cotton, and cause that
part of the dry gun cotton which is not
yet consumed to detonate.
Similar relations may be obtained by
placing a primer in a piece of dry gun
cotton, provided with a recess for the
purpose, and igniting the piece of gun
cotton at any point. In a large number
of experiments, which we personally con-
ducted, the gun cotton was always caused
to detonate after ignition, and by the
combustion in conjunction with the
primer.
In shells we found the action similar.
We believe, moreover, that, by a special
construction and application of the pri-
mer, it will be more difficult to cause it
to detonate than to cause dry gun cotton
to bum.
On the other hand, there is no danger
whatever that, when the dry gun cotton
begins to bum, the shell will burst before
the primer is detonated.
It is therefore quite possible to make
an armor shell, containing wet and dry
gun cotton and a primer, but without a
fuse, burst at the proper time, hence not
too early, since the development of the
flame of dry gun cotton and the trans-
mission of the flame to the primer will
require a certain amount of time.
We do not know whether this has been
determined by experiments, but it is clear
that in case of shells which do not pene-
trate into the armor plate, and are not
designed to, the relations are much more
favorable. These shells would be pro-
vided with as great a charge as possible,
and with a fuse, of course not a slow one.
The shell will either strike the ar-
mor plate at an acute angle and glance
off— in which case it will burst, contrary
to the view of Major Schumann, quite
close to the armor plate — or it will strike
perpendicularly, so that it will be crushed
or flattened, and thus in all cases be de-
tonated, and at the proper time for the
charge to act with full effect, since it
bursts immediately after impact.
We believe, too, that the Schumann
armored constructions are not safe against
the effect of gun cotton shells as they
are against gunpowder shells, and that
therefore gun cotton shells will be of
service against all kinds of armored con-
structions.
We return to the object of our experi-
ments with gun cotton shells, viz., that,
in opposition to the propositions to use a
dynamite cartridge, thrown by means of
compressed air from the bore of a gun,
and in opposition to many other proposi-
tions, and the application of apparatus
already on hand, to throw projectiles
filled with sudden explosives, in all of
which uncommon, complex and very ex-
pensive apparatus, difficult to transport,
is required, we propose to fire at great
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ranges the ordinary shell as a gun cotton
shell, specially proyided with oiir mode of
arrangement, from ordinary guns and
mortars, with the gunpowder charges
now in use. We lay particular stress on
the simplicity of the application of our
gun cotton shells, and, according to our
view, we must add that, under all cir-
cumstances, at least on land, nothing
should ever be used as a moving force
for projectiles but the most compendious
and cheapest source of such power— gun-
powder.
Our constructions relate only to the
filling of the shells now in use with gun
cotton ; no change of material other iJ^an
the charge of the shell takes place ; even
the weight of the filled shell remains un-
changed.
These results we have obtained :
1. By the manufacture of a special,
new and effective granulated gun cotton.
2. By means of a special arrangement
for filling the shells, viz., by filling out
the interstices with paraffine.
8. By the construction of a suitable
primer.
We are convinced that the gun cotton
shell will be of great service, even if it
will not accomplish wonders.
The effect of sudden explosives is over-
rated; on a small part of a heavy armored
plate, for instance, one cannot obtain
nearly the same effect with ever so ener-
getic a sudden explosive as may be ob-
tained with a steel shell from a 30 cm. or
40 cm. gun, but in the first place there
are but few such guns, and in the second
place they cannot be moved about on
land. On land and in the attack and de-
fense of fortifications the limit of pro-
ducing increase in effect by increasing the
caUber is soon reached, and nothing re-
mains but to increase the effect of explo-
sion, and we believe that shells coni^n-
ing sudden explosives will play an im-
portant part in the future, although they
will ncft accomplish all that is expected by
those who overrate the possibilities in the
case; but just because these shells will not
work wonders, we are of opinion that the
sudden explosives must be applied so as
not to alter the artillery material.
We submit these lines to the indulgent
reader with the assurance that, although
we have said much pro domo, we have
also endeavored to carry out the experi-
ments without prejudice and to draw the
conclusions in the same spirit.
SOURCES OP POWER.
From "The Eiurlneer."
In the older treatises on mechanics we
find the sources of power classified under
the heads, "Wind, Water, Steam, Ani-
mals ;*' and,- broadly speaking, these are
still the only sources of power we pos-
sess. But when we deal more in detail
with the subject, we find that vdnd in all
probability owes its capacity for perform-
ing work to the sun, while water is ab-
solutely inert, save as actuated by gravity,
and steam is of course merely an agent
by which heat is converted into work.
Concerning the methods by which animals
perform work we are entirely ignorant,
no physiologist having as yet succeeded
in tracing the sequence of processes by
which food is converted into mechanical
energy. Enough is known, however, to
show that the process has nothing in
common vnth that by which work is per-
formed by heat engines. So that the
analogy sometimes drawn between a man
and a machine must be rejected as far-
fetched, permissible to the poet, indeed,
but not to the philosopher. Further-
more, it is known that the work got out of
food by men and animals is much greater
on the whole than can be obtained from
fuel consumed in the best steam engines.
That is to say, a man or a horse may be
more economical sources of energy, in
one sense, than any machine. Be this as
it may, it is sufficiently evident that we
depend for the performance of all the
work done in the world on two main
sources of power — heat and vital energy.
The action of gravity, it is true, causes
the falling of water, and so gives out
power ; but the water has to be raised
before it can fall, and this raising is
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VAN nostrand's kngikeering magazike.
effected by the beat of tbe srm, wbicb
eyaporates moisture and so indirectly
gives us clouds and rain.
It appears to be not unreasonable that
men should ask themselves now and
then if there are no other sources from
which power may be derived — is there no
other force of nature that can be made
the slave of man? The question has
been put in hundreds of ways, and re-
mains unanswered. The seekers after
motive power have been nearly as nu-
merous and persistent as those who
wasted their lives in search of the philoso-
pher's stone. With the ** perpetual mo-
tion " man we have no patience, and it is
perhaps scarcely necessary to point out
to our readers that we are about to
speak of something very different indeed
from the ordinary notion of perpetual
motion. Inventors who have sought that
have, for the most part, attempted to get
something out of nothing ; that is, in a
word, create energy. There is a wide
difference, however — a great gulf, indeed
— between this and an attempt to still
further explore nature^s secrets in search
of a source of energy — that is to say, of
work — ^now unavailable. Now, in dealing
with this question of 'sources of energy,
it seems to be not impossible that a mis-
apprehension of the nature and bearing
of the laws of the conservation of energy
may do a great deal of harm. It may be
said, for example, that it is quite useless
to search for a source of energy which
can be better or more economical than
what we have now, and much more to
the same effect. But let us ask ourselves
what is this law of the conservation of
energy, on what is it based, and what
would be the consequences to the uni-
verse if it did not exist t Such questions
are very seldom asked, because the num-
ber of men who are at the pains to think
for themselves is small. But when they
are asked, the answer is remarkable.
There is really no reason at all why energy
should be conserved, and so far as our
senses supply evidence, far from being
conserved it is being profusely wasted
every day. Of course, if we go a little
behind the evidence of our senses, we find
that the waste is only apparent, not real.
It is much easier, however, to form an
idea of a universe in which the law of the
conservation of energy has no existence,
than it is to realize a fourth dimension
in space, or even the life of the inhabit-
ants of Flatland. As a help to the reali-
zation of such a universe, we may point
to the fact that the sun has been giving
out energy for millions of years, and that
there is no reason whatever to think that
he has lost any portion of his original
heat In other words, it is simply im-
possible to prove that what we call
energy is not created in the sun. Again^
let us take gravity. We have here the
most stupendous force in nature. There
is no reason to imagine that it is capable
of degradation. If all the planets fell
into the sun, gravity would of necessity
have performed an enormous amount of
work ; but no one can say that after it
was. done gravity would be any the
weaker. It may indeed be said that the
law of the conservation of energy has
only just missed being disproved, if the
words ** conservation of energy " be used
in one sense. So far as can be seen there
is no reason why the line of magnetic
force should not behave like lines of
electrical force or heat force, and admit
of being intercepted or stopped. It
would tiien suffice to put a permanent
magnet under one end of a beam, the
other end of which should be connected
in the usual way with a crank and fly-
wheel. Then, by interposing and with-
drawing a thin intercepting plate at the
proper intervals, we should have a ma-
chine which would work steadily until
it was worn out, without the expenditure
of one farthing for fuel. In the popular
sense of the word, we should create
power ; and the perpetual motion men
would spend their lives in patenting de-
tails, while the principle would be public
property. Has any one the least idea
why magnetic force lines should traverse
every known material! Can any one as-
sert that if this was not the case the ex-
istence of the universe would be impossi-
ble or even difficult t Can anyone assert
with certainty that no means wUl ever be
found for intercepting or dissipating
magnetic rays, without expending energy
in doing sot Finally, is it not possible
to obtain some idea of the cause of mag-
netic force from this very peculiarity of
its behavior ! To put an extreme case,
it may be urged that the law of the con-
servation of energy being true, it is im-
possible to intercept a magnetic force
line. What then is the nature of the
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force which will comply with this condi-
tion ? On the other hand, it is possible
to intercept a heat, light, or electrical
line, and yet the law of the conservation
of energy is not interfered with — ergOy
magnetic force mast possess features
which distinguish it from the other forces
we have named ; from all other forces,
indeed, save gravity. One deduction
seems to be consistent with facts —
namely, that magnetism and gravity are
original or primal forces, and that the
remaining forces — such as light, heat, and
electricity — are derived, built-up, or com-
posite forces. That, in a word, gravity
and magnetism are elements, while light,
heat and electricity are compounds. We
speak of light, heat and electricity as
''forces;" perhaps it would be more
strictly correct to speak of them as
manifestations of force. But what we
have written will serve sufficiently well
to convey our meaning.
The sum and substance of what we de-
sire to convey is that there is nothing
known which renders it absolutely certain
that mankind may not yet find new
sources of energy in nature. No one can
assert positively that it must always be
impossible to make electricity work for
us. If a man had shown Socrates a lump
of coal and told him that it could be con-
verted into work he would have laughed
at him. Our purpose will be served in
writing this article if we make our read-
ers understand that there is as yet at
least no finality in science. There is no
reason, for example, to conclude that it
is absolutely and physically impossible
that sources of power may yet be dis-
covered which are not now dreamed of.
The electricity wiiich now rends the
forest oak, or brings down the lofty edi-
fice in a hideous ruin, may yet be taught
to light our towns. Chemical science
may give us new reactions which will sup-
ply large sources of power. The world
does not yet know everything ; and he
who knows most is least likely to assert
dogmatically that things which do not
exist now never can exist in time to
come.
THERMODYNAMICS.
By DB VOLSON WOOD, C. K., M.A.
Written for Vav No8TBAin>*8 BiiGiNSBBiifo Maqazzke.
1. To find the difference between the
epecific hecUs of a substance graphi-
cally.
Let K„ be the specific heat of a sub-
stance in foot-pounds at the absolute
temperature r for volume constant, and
Ep the specific heat for pressure constant
at the same temperature. Draw two iso-
VoL. XXXV.— No. 6—84 *
thermals corresponding to r and r, in-
definitely near each other, such that
r,— T= A r, and from any point a in the
isothermal r draw ac pai^el to the axis
of X and ab perpendicular thereto ; also
the adiabatics am^j bm^, cm^; then will the
heat absorbed for the path of the fluid
ab be
m^abm^=K„ , a r,
and the heat necessary to raise the tem-
perature A T along the path ac, the press-
ure being constant, will be :
m^acm^=Kj, . at,
the tUtimate values of which will be
m^abm^=K„dry
m^acm^=::Kpdr ;
. •. m^bcm^ = (Kp — K„)dr.
But m^bcm^ is the heat absorbed at
constant temperature during the^expan-
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490
VAN NOSTBANB'S ENGINEERrNO MAGAZINE.
sion from btoc, which was found io be,
in a preceding article, page 268,
m^bcm.=r^ dv,
* * dr
which, compared with the preceding
equation, gives
2. JExamples, a. Find the difference be-
tween the specific heat at constant vol-
ume and at constant pressure for perfect
We have
fw=Rr;
"\dr) v-r"
/dv\_Ii
\drrl>'
which reduces equation (1) to
a well known result.
(2)
b, !Find the difference of these specific
heats for the imperfect gas represented
by the equation
»v=Rt ,
^ TV
We have
(c?r\ R a __v 2a
dr/ " p r^vp "~ T r*vp'
vp
...K.-K.=l(..^.)(..|),
which reduces to (2) for a=0.
(3)
3. Formula modified for liquids and
solids.
In equation (1) the value of -r- may
be found by direct experiment, but in the
case of liquids and solids -^ the rate of
increase of pressure per unit of tempera-
ture cannot be readily found ; and, gen-
erally, for such bodies in the atmosphere,
the pressure may be constant while sub-
jected to changes in temperature. The
relation between volume and pressure
may generally be approximated to by
means of the coefficient of elasticity.
We have generally
But if /> be constant, <^=0, and we have
for such a case :
"KdrJ" \dvjdr'
which, substituted in (1), gives :
which applies equally well to gases. The
reciprocal of l-^| will be found by
periment
ex-
4. JExamples.
a. Applying this to the case of water, we
first observe that at its maximum densi-
ty under the constant pressure of the at-
mosphere, — =0; for which condition
equation (4) gives :
or, the two specifics of water are equal at
its maximum density.
b. Next, find the difference between
these specific heats for water at 25** C.
=77^ F. =538.2° F. absolute.
The volume of a pound of water at its
maximum density under the pressure of
one atmosphere is 0.016 of a cubic foot,
and as the coefficient of cubical expansion
at 25° 0. is 0.00025 per degree Centi-
grade, or 0.00014 nearly per degree F.
at 77° F., we have :
(^y=(0.016 X 0.00014)*=5XlO-i«.
We will take 0.01605 as the volume of
one pound of water at 77° F. under the
pressure of one atmosphere The coeffi-
cient of compression for one atmosphere
is 0.000046 ; hence the compression for
one pound on a square foot will be :
dv 0.01605x0.000046
dp-
2116.3
=10-«X350;
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THEBMODYNAMICS.
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•'•</»" 350'
and equation (4) gives
Kp-K^=538.2 X ^iTr=7.689,
which in ordinary heat units, becomes^ by
dividing by 772,
A:^— ^^=0.0099 very nearly.
5. Ratio of the specific heats.
If at ^ a tangent be drawn to the iso-
thermal bcy and another to the adiabatic
bm^, and the isothermal r+ at approach
r indefinitely, we will ultimately have :
ac
tan. abc ab
tan.a^(/""a3"
ab
ac
'ad
and the areas m^abin^ and rn^acm^ will
ultimately be as ad to ac;
tan, abc ac_ m^acm^ 'Kpdr__Kj,
' ' tan. abd" ad''m^abni^''K^r^K„'
The angle abc is between the tangent
to the isotheraoal and the ordinate/?, and
abd is between the tangent to the adia-
batic and the same ordinate. The value
of this ratio deduced from equation (4)
shows that it is dependent upon K^, but
hat the ratio of the tangents is constant
Y>T perfect gases.
6. A third equation of thermodynamics
in which V and p are the independ-
ent variables.
Let AcB (Fig. 2) be the ultimate path
of tiie fluid; from A let the path, at
first, be subjected to the condition that
B^
the pressure is constant, then will the
path be parallel to OX, which we call
horizontaL If Elp be the specific heat at
constant pressure, the increase of tem-
perature from A to ^ being dr, while the
length of Ab is dv, so that r is a function
of V, we then write
^Mt}"^"'
then wOl the heat represented by MA&m,
be Kpd^r.
At b let the path be vertical to some
point c on the ultimate continuous path,
for which v will be constant, and if K^
be the specific heat at constant volume,
the heat m bcm^ will be K^dpT (the Hue
cm^ is not shown in the figure, and may
be suppHed by the reader) ; hence, ulti-
mately, the heat
MA^m,=MAtfm,=<ffl=Kp<f^r + K^dj,T
which is the differential equation sought
It may be reduced to another form by
finding Ij-j from (1), then ( — 1 from the
same, substituting and reducing, giving
m
This form may be deduced directly
from the two more common forms, which
are:
dK=K„dr-\-r(^J')do,
rfH=Kprfr-r(~)^p;
(7)
(8)
by multiplying the former by Kp and the
latter by K^ and subtractii^T ; gi'ving at
once.
If the path of the fluid be an isother-
mal, it would, at first sight, seem that
equation (6) requires a knowledge of the
specific heats in order to find the heat
absorbed, whereas, according to equations
(7) and (8) the specific heats disappear
for r constant. But for r constant equa-
tions (7) and (8) give
'C^)*=-4:)*.
and this, substituted in equation (6), gives
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VAN itostbaitd's ekoineebino maoazine.
which is the same as (6) and (7) for r
constant, showing that the apparent re-
tention of the specific heats for this par-
ticular case is only apparent
7. Other processes.
In this and the preceding article, the
passage from A to B has been by three
different combinations of paths: first,
by isothermal and vertical lines ; second,
by horizontal and isothermal lines ; and,
third, by horizontal and vertical lines. It
is evident that other elementary paths
might be followed, as for instance, an
isothermal followed by an adiabatic, and
other combinations with the adiabatic, or
the right lined paths might be obliqae,
but to make these combinations useful
their properties must be known, which
would add greatly to the complexity of
the analysis without being of any advan-
tage.
8. The Second Law,
We return again to the consideration
of this much-discussed subject The
literature upon this subject shows that
writers not only differ in the formal state
ment of the second law of thermody-
namics, but, unfortunately, are not agreed
as to what constitutes this law. Some
even ignore it, and attempt to develop
the subject from the first law only (like
Zeuner), while others state the principles
involved in the subject without dignify-
ing them as Imos, Thus, Rankine states
two laws, and Sir William Thomson gives
two propositions, the second of which
depends for its demonstration upon the
axiom, It is impossible by means of in-
animate material agency to derive me-
chanical effect from any portion of
matter by cooling it belovo the tempera-
ture of the coldest of surrounding objects,
(Math, and Phys. Papers, pp. 178, 179) ;
and Clausius states a First Main Prin-
ciple, a Second Main Principle, and a
New Fundamental Principle, the last of
which is contained in the axiom: "A
passage of heat from a colder to a hot-
ter body cannot take place without com-
pensation."* (Clausius "Mechanical The-
ory of Heat," Browne's Translation, p. 78.)
The question arises. What shall the sec-
ond law be t Shall the two axioms just
quoted be considered as the second law T
They are not unfrequently referred to as
such. McCulloch in his Mechanical The-
ory of Heat, page 162, states that Clau-
sius' axiom was less obvious than Thom-
son's, but the latter writer claims that
" either is a consequence of the other."
(Papers, p. 181.) Or, shall we consider
Bankine*s second law as the only true
second law! and if so, which of his
several statements of it shall we accept
as the valid one ? for they are not identi-
cal, nor do they all cover the same
ground. Or, shall we consider Thomson's
and Clausius' extension of Carnot's prin-
ciple of a reversible cycle as the second
law?
One or another of these three general
forms is referred to as the second law,
but it would be more agreeable to the
student if the second law were so defined
as to be generally accepted and recog-
nized as such. No philosopher has power
to compel the acceptance of a principle,
much less to restrict it a definite order.
The statements of the founders of a sci-
ence have great force with their follow-
ers, but where several investigators are