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should be as few in number as possible, and rounded rather than acute;
for a sharp or abrupt bend materially diminishes the velocity of the
draught. Two or more pipes opening into the same chimney should
have separate flues ; when they open into the same flue, the pipe that
draws best will interfere with the draught in the others, and set up
downward currents.

The air consumed by combustion escapes by the chimney, and
tends to create a vacuum in the room ; but it is steadily replaced by
the atmosphere which rushes in at every available opening. This rush
is strongest at the lowest openings (those nearest the earth), and here
the whole amount enters if the space is sufficient. On the other hand,
and for the reasons before given, the warmer (lighter) and fouled air
within has a constant tendency to escape at the highest points ; and it
is here, therefore, that ventilators should be placed to allow its exit.
Thus it is that, when a door is opened, the warmer (foul) air escapes in
a current at the top, and the colder (fresh) from the outside rushes in
at the bottom. This may be shown by a lighted taper held in these
situations — the flame in each case taking the direction of the current.
When the outside air is the warmer, and per consequence the lighter,
as on a very warm summer day, the direction of the currents, other
things being the same, will be reversed — the fresh air coming in above,
and the cool air within escaping below. But, owing to the large
amount of heat radiated from the pupils — the normal tempei*ature of



-rr-kr^v^rfi



538 THE POPULAR SCIEXCE MOXTHLY.



the human body averaging 3T*5° Cent., or 99° Fahr. — the lighter air is
nearly always within. Therefore, if on the sheltered side a window is
lowered at the top, or on any side if the air be calm, the foul air will
escape above it ; if raised from below, fresh air will enter beneath.
But ordinarily it is sufficient to fully provide for the escape of the
fouled air — the fresh, as a rule, will not need so much attention ; yet it
is better to make ample provision also for this. The best method is
by ventilators in the walls — say of a foot square in section, or there-
about — raised but a few inches above the floor below, and lowered
but a few inches below the ceiling above ; or otherwise at the highest
points of the ceiling itself. In this way the currents that are likely to
blow on the children's shoulders when the windows are raised are
avoided, a matter of importance ; for a draught of cold air, blowing
upon the shoulders from behind, arrests the action of the skin — prob-
ably through the spinal sensory nerves — and causes what is commonly
known as a "cold." Even when windows are lowered at the top,
draughts will occasionally blow upon the pupils ; and, the lower the
windows are set in the wall, the stronger and more uncomfortable and
injurious is the draught. In order to prevent these draughts, the win-
dows should be set high in the wall and lowered on the sheltered side
whenever possible. An ingenious contrivance for the prevention of
draughts through open windows has been suggested by Dr. Swin-
burne, in a paper read before the last annual meeting of the New York
State Medical Society. It consists in the attachment of one end of a
strip of unstarched muslin to a spring roller fastened to the casement
above, and the other end to the upper edge of the window itself. On
lowering the window, the muslin is unrolled, and thus stretches across
the vacant space. Being held tense by the spring of the roller, it
effectually shuts off all draught, while it allows the escape of the foul
gases within, and the slow but steady entrance of fresh air.

Even should there be no currents through ventilators or open win-
dows, yet the foul gases will make their escape by diffusion ; for, ac-
cording to the law of diffusion, there is a rapid interchange between
gases in free communication. Of course, the outflow of the inside air
very materially hastens the rapidity of the interchange ; but the out-
flow will not, can not, be very rapid if there is not sufficient provision
for the entrance of fresh air other than through the same apertures
through which the outflow itself takes place. Again, the warmer the
day, the less the difference between the temperature of the inside and
the outside air ; hence the buoyancy of the inside air is less, and con-
sequently the ventilation not so effective ; so that more attention and
greater facilities must be afforded it. Ventilators should never be
placed in the hall ; here they do but little good. The doors leading
from the hall to the rooms are usually closed, and, even if open, the
buoyancy of the air as a factor in ventilation is nearly eliminated ; for
there is a partition between the hall and the room, so that the light



'if'^^sr^'



RIG IX AND USES OF ASPHALT. 539

air and the lighter animal exhalations would be compelled to descend
to the level of the top of the communicating door in order to escape.
This they can not do, for it is in opposition to gravity. If no other
outlet is provided, the only ventilation will be by diffusion through
the doorway with the purer air in the hall. The animal exhalations
will fill the room from the ceiling to the level of the top of the com-
municating door, and there remain. It would cost but a trifle to have
one or two ventilators put in the ceiling of a school-room where there
are none in the walls ; and school directors could not make a better
investment of the money. Children will not study, and can not be
persuaded or compelled to study diligently, in the foul and stifling air
of a crowded and wretchedly ventilated room. It may be safely as-
serted that in a majority of our schools the ventilation is insufficient,
or not properly attended to, either on account of lack of knowledge or
attention on the part of the teacher, or the defective construction of
the building. A sanitary inspection should be made of every school
in the State by a competent medical inspector ; and all the schools
found defective in this (or any other way injurious to health) should
have all such defects remedied, or otherwise be condemned as unfit for
school purposes, with the imposition of penalties for using them as such.
A school-room should have a high ceiling ; contain from two hun-
dred to three hundred cubic feet of air to each pupil ; have one or
more ventilators in the ceiling, or the walls near the ceiling ; have
long, high windows arranged to slide upward from beneath, and down-
ward from above. All the children should be sent out at recess, if
only for a short time, in order to have their clothing — saturated as it
usually is by animal exhalations — exposed to the purifying influence of
the open air, and doors and windows thrown open in order to com-
pletely change the air within. Stoves, chimneys, pipes, etc., should be
carefully looked after, and any accident or defect promptly attended
to, or immediately reported. Children convalescing from contagious
diseases should be excluded from school for weeks, or months, accord-
ing to the recognized limit of contagiousness of the disease. It should
not be forgotten that the school and tlie church are the two great
centers for the communication of contagious diseases ; and that both
are active in this way in direct proportion to the insufficiency of the
ventilation.



origi:n" and uses of asphalt.

Br LEON MALO, C. E.

BITUMEN" appears in nature as an accidental mineralogical prod-
uct, under the most diverse and often most inexplicable condi-
tions. It is found sometimes in the native state, sometimes mixed
with clays, sometimes as the cement of conglomerates, sometimes im-



540 THE POPULAR SCIENCE MONTHLY.

pregnating limestones. The last combination produces the mineral
commonly called asphalt. When the bitumen contained in any of
these substances is chemically isolated, it appears always a nearly
identical substance, in composition, consistency, and appearance, ex-
cept that the empyreumatic odor that characterizes it may become alli-
aceous in volcanic countries. Asphalt is doubtless one of the most con-
siderable and valuable of the forms in which bitumen appears. It is a
soft limestone, naturally and closely impregnated with that substance.
When a specimen of it is examined under the microscope, each grain
of it appears to be immersed in a pellicle of pure bitumen, by which
it is cemented to the adjoining particles. It is thus a species of very
fine-grained bituminous conglomerate. WTien a lump of this rock is
heated to a temperature rising from 176° to 212°, the pellicle of bitu-
men is melted, the cohesion of the asphalt is destroyed, and it crum-
bles into dust. If it is taken while it is still hot, or if it is heated again
after it has become cool, and strongly compressed, the particles will
adhere again, and the stone will recover, after cooling, precisely the
consistency and appearance it. had originally. The employment of
compressed asphalt for pavements is founded on this property.

Asphalt, or bituminous limestone, is generally found in the Jurassic
strata, in regular beds of a lenticular shape, which are uniformly cut
in two by a stream of water. Sometimes the bed is single, at other
times it is multiple ; there are formations containing seven beds,
one above the other, and distinctly separated by strata of white lime-
stone.

Different views prevail respecting the origin of asphalt and the cir-
cumstances under which it is formed. Some believe that the bitumen
was already in existence when the calcareous formation took place,
and that the particles of limestone were deposited in a bituminous sea.
Others consider that the bituminous matter is derived from the organic
matter associated with the shells that have furnished the carbonate of
lime ; and other more hazardous hypotheses have been advanced. A
careful observation of asphaltic formations has led me to adopt what
appears to me to be a more plausible theory.

It is permitted to suppose, from indications furnished by the study
of bituminous districts, that in some geological epochs, which have yet
been only imperfectly determined, accumulations of organic matter,
buried under enormous masses of Jurassic limestone, and heated by
the central fire, became vaporized, and in that condition sought a pas-
sage through the crust of the earth (Fig. 1). In time the crust cracked,
and a fissure was formed. The bituminous vapors, compressed by in-
calculable pressure, forced themselves through the way that was opened
to them, and passed by such strata as were too compact to be pene-
trated ; but, when they reached the oolite, they found on either side
of the fissure beds of a limestone soft enough to admit of their impreg-
nating it (Fig. 2). As long as the pressure lasted, the bitumen con-



ORIGiy AyD USES OF ASPHALT.



541



tinned to insinuate itself through tlie pores of the limestone, and to
fill its infinitesimal cavities.

Mineral asphalt is relatively a soft stone. It becomes more com-
pact as the temperature diminishes, but yields ninder the influence of




heat to such a degree that an exposure of a few days to the summer
sun will sometimes cause it to crumble. This property has induced
the application of the compressed material to the making of pavements.
Its fitness for this purpose seems to have been suggested by accident.
"When the mineral was first quarried, the pieces which fell along the
road from the wagons carrying it w^ere ground up by the Avheels, and
were finally compressed again by the continued passage of the wagons
over the dust, so as to form a kind of spontaneous pavement. A Swiss
engineer, M. Merian, acting upon the suggestion of this incident, as-
phalted a part of the road from Travers to Pontarlier, in a rough way,
but with a satisfactory result. In the next year (1850), M. Darcy, in-
spector-general of bridges and highways, recommended asphalt as a
material for pavements in a report to the Minister of Public Works.
The first asphaltic pavement was laid in Paris in 1854.



542



THE POPULAR SCIENCE MONTHLY.



The mineral appears in industry, under a still more useful form
than the compressed form, as asphaltic mastic. This is made by throw-
ing the powdered mineral into a bath of seven or eight per cent, of
its weight of liquid bitumen, and mixing the whole thoroughly while
it is cooked for five or six hours. The substance produced, although




Fig. 2. — Probable Foiimation of Asphalt aftek Erosion.



chemically the same, except for the difference in the relative propor-
tions of bitumen and limestone, is physically entirely different from
asphalt. It can not be pulverized by heating, but forms a paste in
Avhich the two ingredients seem to be perfectly combined, and which
may be molded into desired forms. The manufacture of the mastic
has become an important industry. The annual production of the
French shops alone must amount to fifteen or twenty thousand tons.

In " La Nature," of April 9th, Mr. A. Woeikofen, of St. Petersburg,
describes the asphaltic beds of Russia, which occur on the grand curve
of the Volga, or the arc of Samara, a short distance above the city of
Syzran. They are not deposited in the Jurassic formation, as are those
in France, Switzerland, and Germany, but in a dolomitic limestone of
the lower Carboniferous series. The mineral is rich in bitumen, of



WT



m^



THE UNIT IN PLANT-LIFE. 543



less fusible quality than the bitumens of France and Switzerland, and
has not been produced in the compressed form. It is extensively made
into mastic, the fabrication of which already amounts to ten thousand
tons a year, and is rapidly increasing. — La Nature.



THE UNIT IN PLANT-LIFE.

By BYRON D. IIALSTED, Sc. D.

MAN, being himself distinctly individualized, endeavors to find
the unit of existence in all other forms of life. He meets with
no great difficulties among the higher animals, but is perplexed and
sometimes discouraged when search is made for the individual in the
lower animals and in plants.

A child is an easily-recognized unit of life at its birth, and is no
more than a single individual when it has reached mature middle life,
or the decline and decay of old age. A limb may have been lost on
the field of battle, or an eye removed by a surgeon, but there is no re-
placement of the lost parts. The human individual may suffer divi-
sion, but it is a mutilation, and not a multiplication of the living unit.

In some respects the seed of a plant is analogous to the young of
the higher animals ; it is the result of a sexual union and the starting-
point of a continuation of the species. For these and other reasons
the seed may be, and has been, called the unit of life in the higher
plants. But what possibilities are contained within the coats of a
single seed when the proper conditions for its growth and propagation
are secured ! When we look beyond the dry and inactive seed, which
can be held upon the tip of the little finger, and note what it may
produce ; when we know that such a single seed has been the starting-
point of a variety of fruit that now has its representatives as full-
grown trees in thousands of orchards all througli this broad land, we
must either expand our idea of a plant-unit until it is too great and
comprehensive to be of service, or seek some other basis of individu-
ality than that which is in some respects analogous to the accepted one
among the higher animals. The idea of the identity of the individual
among the more complex and perfect forms of existence in the two
kingdoms of life may be dismissed, because the methods of propaga-
tion in the two are far from the same.

If we take some common plant of the higher orders — any tree or
shrub, or even a herb — it will be found, upon careful study of its
structure, that there is an almost monotonous repetition of parts. It
will also be observed that these parts may be grouped under three
heads, to which the common names of root, stem, and leaf are applied.
The root includes that portion of the plant, whether aerial or subter-



544 THE POPULAR SCIENCE MONTHLY.

ranean, the young gro\ring extremities of which are protected by a
layer of tissue called the root-cap. The stem is the axis of the plant,
and is the part which bears the leaves, and includes those peculiar
growths, such as thorns, runners, tendrils, etc., which serve a special
purpose in the plant economy. The leaf is a lateral outgrowth from
the stem, and is usually a flat, green expansion, but may assume the
form of scales, highly-colored and strangely-shaped floral parts, etc.
The fact that the largest tree and the smallest herb are alike made up
of a greater or less number of these plant'inemhers^ as they are termed,
leads naturally to the thought that any mass of plant-tissue having a
root, a stem, and a leaf, may be a plant individual, and that, when a
number of these members are intimately associated together, a com-
munity of plant individuals is formed. This is the modern concep-
tion of a tree or shrub — a living structure, which is the result of the
combined, harmonious, silent working of many generations of indi-
viduals. Out of the three members are made all the multiplicity of
forms and structures which meet our eyes as we look upon the higher
forms of vegetation. They all have a common origin in the apical
growing-points, and are indistinguishable in their earlier stages, but
become differentiated as they develop, and at last assume their char-
acteristic, mature forms. The growing-point of a stem (piaictum
vegetatlonis) is a conical apex, a little below which the leaves appear
first as very slight swellings. By their more rapid growth than the
stem, they reach above the growing-point, and, folding over each other,
cover it more or less completely. As the stem elongates, the leaves
upon the older portion are gradually separated, and an ordinary stem,
with its leaves arranged at regular intervals, results. A bud is sim-
ply a young stem, with its undeveloped leaves. A developed stem
is a series of similar parts, those parts being a leaf with a portion of
the stem above and below it, each borne upon its predecessor, and in
turn bearing the next one in the series. These similar parts have
received the name phyton, and are very generally considered as the
individuals out of which a plant community is built up. The gardener
divides the young branches of the verbena, salvia, etc., into these phy-
tons, and jjlaces them in moist sand, where they soon begin an inde-
pendent existence, and in time reproduce their kind. In the operation
of grafting, a similar portion of a plant community of one variety is
given a fitting place for growth in another, and by its growth and
multiplication of phytons a new colony is established. With this
view a tree or shrub may form an individual part of a landscape, but
not in ths same sense that one may speak of a cow or a horse. The
tree more nearly resembles a swarm of bees ; there is a similarity of
unity between a shrub and a hive. The larger part of the shrub is
made up of foliar units, with ordinary leaves for the elaboration —
gathering, so to speak, of the food for the whole community. These
are the icorJcers and the ?ieuters of the vegetable "hive." Other plant



r^



THE UNIT IX PLANT-LIFE. 545



individuals devote their energies to the production of new plant-units,
namely, the stamens — the male units of the flowers — which perish as
soon as their transient but important work of fertilizing the pistil is
accomplished ; these are the drones. The pistil is the central part of
the flower, and around which all the work of propagation converges
and the labors of the year culminate, and from which the new indi-
viduals, the seeds, go forth to develop into free and independent col-
onies. In several respects this pistil is queen of the congregated vege-
table units.

There are some objections to the phytons being considered the
unit of vegetable life. The division of a plant may be carried be-
yond it, and life and growth of the parts still be maintained. Thus
buds may arise from petioles, or leaf-stalks, and from the veins of
the leaf, as in the ordinary propagation of the begonia, and very
strikingly in the bryophyllum. Buds may start from the woody bundles
of roots, as in the sweet-potato, poplar, or the cut stems of the elm,
willow, etc. These many cases of a seemingly spontaneous growth
have led to another definition of the plant-unit which is formulated
briefly as follows : A plant individual is that smallest part that can
grow when separated from its former place in a plant community, and
given the fitting conditions for growth by itself. In most cases this
" smallest part " is the phyton, or a portion of the stem with its leaf,
and the bud or growing point which it bears in its axil. This young
lateral bud, which is frequently so small as to be unseen by the naked
eye, is, in fact, the vitalized, undeveloped stem that is to increase in
size if growth takes place. The writer is of the belief that in this
growing-point the individuality of higher plants should be located.
If there are two buds upon the phyton, it seems proper to say there
are two individuals, as there are two distinct points of growth, and
two branches may result therefrom.

If the phyton is to be considered as the plant-unit, we must seek
for another unit of life for those plants in which no phyton elements
exist. The unit of growth is the cell ; in it, either alone or in con-
nection with other cells, all the functions of life are performed. Cells
compose the growing tissue of every plant ; in them resides that vital-
ized substance called protoplasm, in which all life-changes take place,
and from which all structures are built up.

Many of the lower plants are unicellular, as, for example, the com-
mon yeast-plant, bacteria, etc., among fungi, and the desmids and
diatoms among algffi. They increase in number by a simple division
of the cell into two, each half increasing in size and dividing as did
its parent. The individual among such plants is evidently the single
cell. As we pass a little higher in the scale of vegetable life, it is
found that though the cells are associated together in filaments, or
lamina^ they are, in most respects, very independent, losing only a trifle
of their originality by being associated in the simplest form of a com-
voL. XIX. — 35



546 THE POPULAR SCIENCE MONTHLY.

munity. As we pass upward in the scale, the differentiation increases,
and there is a consequent division of labor, some of the cells being de-
voted to one kind of work, while others engage in a special labor for
the community. Instead of the sum of the vital forces possessed by
an individual being confined to a single cell, they are scattered through
a large amount of growing tissue.

The seat of vitality is protoplasm, and wherever there is enough of
this vitalized substance to grow and reproduce its kind, there we have
an individual — a unit of life. It may be concentrated in a single cell,
or distributed through many cells, the number and disfribution being
determined by the amount of dependence of the growing cells upon
each other. The greater the division of labor, the higher the form of
life, and the more difficult to recognize the individual ; but, whenever
it is found, it consists of a mass of protoplasm, usually contained in
one or more cells, capable of growth under proper conditions, and
ultimatolv reproducins? its kind.



"THE ELECTKIC STORAGE OF ENERGY."

SOME few weeks ago a letter appeared in the "Times," signed
" F. R. S.," describing a "box of lightning" which the writer had
brought over from Paris for the purpose of submitting it to Sir Wil-
liam Thomson. Since then a long discussion has taken place on the
subject of the invention and its usefulness. To begin with, we fully
share the regret of Professor Tyndall, who has written a letter on the
matter, that so much loose nomenclature has been introduced into the
subject. The term " electric storage of energy " appears to us to be
singularly unhappy. What is known as a condenser, or a Leyden-jar,
is truly an instrument for the electric storage of energy, because,
when charged, its parts are in a condition of molecular strain, which
is recognized as an electrical phenomenon ; and the release of this
state of strain invariably produces at first some of the phenomena of
electricity in motion. But in the case of M. Faure's secondary bat-
tery, which is the invention under discussion, although it is charged



Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 67 of 110)