September 10, 1870.] THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
207 
at 18° C., and the latter is a dark yellow crystalline 
precipitate. The chloromercurate forms colourless 
rhomboidal laminae. The iodomercurate is crystal¬ 
line and soluble in boiling alcohol. 
The author concludes his memoir by stating the 
relations which the new bases bear to those pre¬ 
viously known. The new bases exist in very small 
amounts in opium. A sample containing 8 - 3 per 
cent, of morphia gave 0’0058 per cent, of laudanine, 
the same quantity of lanthopine, and 0‘0033 of coda¬ 
mine. 
Codamine and laudanine are homologues of mor¬ 
phia and of codeia. Lanthopine is the superior 
homologue of papaverine. Ptelated to the latter two, 
as oxidation derivatives, are cryptopine and narceine 
on the one hand, rlieadine and rlieagine on the other. 
It has been stated incorrectly that cryptopine is 
soluble in potash. Oil of vitriol colours cryptopine 
dark green .—Annalen der Chem. und Pharmacie, 
cliii. 47. 
WHAT IS ENERGY ? 
BY BALFOUR STEWART. 
IT. 
In our first article it was shown that energy, or 
the power of doing work, is of two kinds, namely, 
energy due to actual motion, and that due to position. 
We ended by supposing that a stone shot vertically 
upwards had been caught at the summit of its flight 
and lodged on the top of a house; and this gave rise 
to the question, What has become of the energy of 
the stone? To answer this we must learn to re¬ 
gard energy, not as a quality , but rather as a thing. 
The chemist has always taught us to regard quan¬ 
tity or mass of matter as unchangeable, so that amid 
the many bewildering transformations of form and 
quality which take place in the chemical world, we 
can always consult our balance with a certainty that 
it will not play us false. But now the physical phi¬ 
losopher steps in and tells us that energy is quite as 
unchangeable as mass, and that the conservation of 
both is equally complete. There is, however, this 
difference between the two things—the same particle 
of matter will always retain the same mass, but it 
will not always retain the same energy. As a whole, 
energy is invariable, but it is always shifting about 
from particle to particle, and it is hence more difficult 
to grasp the conception of an invariability of energy 
than of an invariability of mass. For instance, the 
mass of our luminary always remains the same, but 
its energy is always getting less. 
And now to return to our question, What has be¬ 
come of the energy of the stone? Has tins disap¬ 
peared ? Far from it; the energy with which the 
stone began its flight has no more disappeared from 
the universe of energy than the coal, when we have 
burned it in our fire, disappears from the universe of 
matter. But this has taken place:—the energy has 
changed its form and become spent or has disap¬ 
peared as energy of actual motion, in gaining for the 
stone a position of advantage with regard to the 
force of gravity. 
If we study this particular instance more minutely, 
we shall see that during the upward flight of the 
stone its energy of actual motion becomes gradually 
changed into energy of position, while the reverse 
will take place during its downward flight, if we now 
suppose it dislodged from the top of the house. In 
tliis latter case the energy of position with which it 
begins its downward flight is gradually reconverted 
into energy of actual motion, until at last, when the 
stone reaches the ground, it has the same amount of 
velocity, and, therefore, of actual energy, which it 
had at first. 
Let us now revert, for a moment, to the definition, 
of energy, which means the power of doing work, 
and we shall see at once how we may gauge nume¬ 
rically the quantity of energy which "the stone pos¬ 
sesses, and, in order to simplify matters, let us sup¬ 
pose that this stone weighs exactly one pound. If, 
therefore, it has velocity enough to carry it up one 
foot, it may be said to have energy enough to do one 
unit of work, inasmuch as we have defined 1 pound 
raised 1 foot high to be one unit of work; and in like 
manner if it has velocity sufficient to carry it 16 feet 
high, it may be said to have an energy equivalent to 
16 units of work or foot-pounds as those units are 
sometimes called. Now, if the stone be discharged 
upwards with an initial velocity of 32 feet per second, 
it will rise 16 feet high, and it has, therefore, an 
energy represented by 16. But if its initial velocit} 7 
be 64 feet per second, it will rise 64 feet high before it 
turns, and will, therefore, have energy represented 
by 64. Hence we see that by doubling the velocity 
the energy is quadrupled, and we might show that 
by tripling the velocity the energy is increased nine 
times. This is expressed in general terms by saying 
that the energy or quantity of work which a moving 
body can accomplish varies as the square of its velo¬ 
city. This fact is well known to artillerymen, for a 
ball with a double velocity will penetrate much more 
than twice as far into an obstacle opposing its pro¬ 
gress. 
Let us now take the stone or pound-weight having 
an initial velocity of 64 feet per second, and consider 
the state of tilings at the precise moment when it is 
48 feet high. It will at that moment have an actual 
velocity of 32 feet per second, which, as we have- 
seen, will represent 16 units of work. But it started 
from the ground with 64 units of work in it: what 
therefore has become of the difference—or 48 units ?' 
Evidently it has disappeared as actual energy; but 
the stone, being 48 feet high, has an energy of posi¬ 
tion represented by 48 units ; so that at this precise 
moment of its flight its actual energy (16), plus its 
energy of position (48), are together equal to the 
whole energy with which it started (64). 
Here, then, we have no annihilation of energy 7 , 
but merely the transformation of it from actual energy 
into that implied by position ; nor have we any crea¬ 
tion of energy when the stone is on its downward 
flight, but merely the retransformation of the energy 
of position into the original form of actual energy. 
We shall presently discuss what becomes of this 
actual energy after the stone has struck the ground; 
but, in the meantime, we would repeat our remark 
how intimate is the analogy between the physical 
and the social world. In both cases we have actual 
energy and energy of position, the only difference 
being that in the social world it is impossible to mea¬ 
sure energy with exactness, while in the mechanical 
world we can gauge it with the utmost precision. 
Proteus-like, this element energy is always chang¬ 
ing its form ; and hence arises the extreme difficulty 
of the subject, for we cannot easily retain a sufficient 
grasp of the ever-changing element to argue experi¬ 
mentally regarding it. All the varieties of physical 
energy may, however, be embraced under the two 
m 3 
