Familiar Talks on Science-World-Building and Life. Earth Part 8

Before entering upon the great subject of water and ice--two of the most tremendous factors in world-building--let us consider a small matter, so far as its permanent effects are concerned, yet one which enters largely into the comfort and health of mankind, and which, though an animal, may be discussed where it belongs--under "Water."

There are few things more familiar about the ordinary household than a piece of sponge, and yet, perhaps, there are but few things about which there is so little known. The sponge had been in use many, many years before it was given a place in either the animal or vegetable kingdom.

The casual observer, because he saw it attached to a rock, jumped to the conclusion that it was of vegetable origin. But after being kicked back and forth, so to speak, from one kingdom to the other, even by what are called well-educated people, it has finally been received into the family of animals; a dignity in which the sponge itself seems to take but little interest.

The sponge is found in the bottom of the sea; at no very great depth, however. It is usually attached to a rock or some other substance and it is due to this fact chiefly that it has been cla.s.sed as a vegetable. At least one scientist has attempted to give it a place between the two kingdoms, but this only adds confusion without giving any satisfactory explanation of its origin. It seems to belong to a very low order of animal life. It breathes water instead of air, but probably, like many other water animals, it absorbs the oxygen from the air which is more or less contained in the water. There is a process of oxidation going on within the sponge in a manner somewhat as we find it in ordinary animal life, and like the animal it expels carbon dioxide. All this, however, is carried on apparently without any lungs or any digestive organs, or in fact any of the organs that are common to the animals of the higher order. The sponge, however, as we see it in our bathrooms, is only the framework, bony structure, or skeleton of the animal.

The sponge is exceedingly porous and readily absorbs water or any fluid by the well-known process of capillary attraction. The sponge fiber is very tough and is not like anything known to exist in the vegetable kingdom. The substance a.n.a.lyzes almost the same as ordinary silk, which all know is an animal product. If we burn a piece of sponge it exhibits very much the same phenomena as the burning of hair or wool, and the smell is very much the same.

The structure of a piece of sponge when examined under a microscope is a wonderfully complicated fabric. Under the microscope it shows a network of interlacing filaments running in every direction in a system of curved lines intersecting and interlacing with each other in a manner to leave capillary openings.

It is a wonderful structure, and one that a mechanical engineer could get many valuable lessons from. It will stand a strain in one direction as well as another. There are no special laminations or lines of cleavage; it is very resilient or elastic, and readily yields to pressure, but as readily comes back to its normal position when the pressure is relieved. If we examine the body of a sponge we shall notice that there are occasional large openings into it, but everywhere surrounded by smaller ones. If we should capture a live sponge and place it in an aquarium with sea water, where we could study it, we should find a circulation constantly going on, and that water was constantly sucked in at the smaller openings all over the outside of the sponge and as continuously ejected from the large openings. This process const.i.tutes what corresponds in the higher order of animals to both respiration and blood circulation, combined. The sponge feeds upon substances that are gathered up from the sea water, and breathes the air contained in the same, so that it breathes, eats, and drinks through the same set of organs.

When we first capture a live sponge from the sea it has a slimy, dirty appearance, and is very heavy. The sponge is found to be filled with a glutinous substance that is the fleshy part of the animal. It is very soft and jelly-like, and after the sponge is dead it is readily squeezed out, by a process which is called "taking the milk out," which leaves simply the skeleton, the only useful part as an article of commerce.

This fleshy substance, in life, has somewhat the appearance and composition of the white of an egg.

The mechanical process by which the sponge takes its nourishment is exceedingly interesting. There are small globe-shaped cells with openings through them that are lined with little hairlike projections that move in such a manner as to suck the water in at one side of the cell and push it out at the other. These little fibers are technically called "cilia." We might describe them as little suction pumps that are located at many points in the sponge, all acting conjointly to produce a circulation through the finer openings or capillary vessels and finally discharging into the larger chambers which carry off the residue. If we should a.n.a.lyze the water as it is sucked into the sponge and that which issues from it through the larger openings, we should find a difference between the two. The expelled water would contain more or less carbon dioxide.

There are many different varieties of sponge, and, while they all possess certain characteristics in common, they are still very different in many respects. Some of them are large and coa.r.s.e, while others are exceedingly soft and velvety. What is called a single sponge is a colony of animals rather than a single animal; at least they are so regarded by zoologists. This can hardly be true if we regard the sponge itself as a part of the animal. If the sponge is simply regarded as the house in which the animal lives then it becomes a great tenement with numerous occupants. But it is a tenement upon which the life of the sponge depends, and is a part of it.

The sponge could not breathe without the fibrous structure in the cells containing the machinery for producing the circulation. It will be seen that the sponge, while it is an animal, is of the very simplest variety, so far as its organs are concerned. True, its framework is very complicated, but the organs for sustaining the life of the animal are the simplest possible. The little self-acting pumps pull the water into the sponge through the smaller openings, where it appropriates the food substance from the water and where a chemical action takes place which builds up the fleshy substance of the animal, and then expels the residue which is not needed to support its life.

Simple as it is, however, as a mechanical structure, the life and growth of the sponge is as mysterious as that of the most highly organized animal or even the soul of man. We can study out the structure of a plant or animal; we can a.n.a.lyze it and tell what are the elements of which it is composed; we can describe the mechanical operations that are carried on and the chemical combinations that take place, but no man has ever yet solved the mystery of life, even in the lowest form--whether animal or vegetable.

The sponge, whether considered as a single or compound animal, has the power to reproduce itself, and here the mystery of life is as much hidden as it is in G.o.d's highest creation. It has been stated that every sponge contains a large number of separate cells which carry on the operation of circulation and respiration, and may be likened to the heart and lungs of an animal of a higher creation. Zoologists claim that each one of these cells represents a separate animal, living in a common structure. However this may be, it is an interesting fact that the sponge has the power of secreting ova that grow in large numbers in little sacks until they have reached a certain stage of progress, when they are expelled from the mother sponge and turned adrift in the great ocean to struggle for their own existence. These eggs do not differ much in their structure and composition from an ordinary hen's egg, except that there is no sh.e.l.l, only a skin provided with little fibers called cilia, that project from it, and by the movement of these the embryo sponge is able to propel itself through the water. It thus lives until it has reached a certain stage of development, when it seeks out a pebble or rock, to which it attaches itself at one end--preparation for which has been made by its peculiar structure during its life when it was free to float around through the water. It is now a prisoner and chained to the rock it has selected for the foundation of its home.

Having no longer any use for the little cilia, which enabled it to swim through the water, it now loses them. Here is a beautiful ill.u.s.tration of how nature provides for the necessities of the smallest things, and how when the necessity that demanded a certain condition pa.s.ses by the condition pa.s.ses with it. The embryo begins to show a fibrous development, which is the beginning of the framework of a new sponge.

Evolution goes on, every step of which is as mysterious as a miracle, until the growing thing is a full-grown sponge, equipped with the means for respiration, circulation, feeding, digestion, and reproduction.

Sponges grow in the bottom of the sea at different depths. They are obtained by divers who make a business of gathering them. The best sponges are called the Turkish sponge, which are very soft and velvety, and may be bleached until they are nearly white by subjecting them to the action of certain acids. The divers become very expert, but they do not have the modern equipments of a diving suit. The Syrian divers in the Mediterranean go down naked with a rope attached to their waists and a stone attached to the rope to cause them to sink, together with a bag for carrying the sponges. They have trained themselves until they can remain under water from a minute to a minute and a half, and in that time can gather from one to three dozen sponges. The ordinary depth to which they descend is from eight to twelve fathoms. But a very expert diver will go down as far as forty fathoms. The better cla.s.s of sponges are said to grow in the deeper waters. The coa.r.s.e inferior sponges are called the Bahama sponge. This sponge is of a peculiar shape, growing more like a brush, with long bristly fiber.

The trade in sponges is quite large. The consumption in Great Britain alone amounts to about $1,000,000 per annum.

The sponge as an animal possesses many advantages over his more aristocratic neighbor, man. He breathes but he has no lungs, and therefore cannot have pneumonia. He digests his food, but he has no stomach, and therefore never has dyspepsia, gastritis, or any of the many ailments that belong to that much abused organ. He has no intestines, and therefore cannot have appendicitis or Asiatic cholera or any of the long train of diseases incident to those complicated organs.

He has no nervous system--oh, happy sponge!--therefore he cannot have nervous prostration, hysteria, or epilepsy. He has no use for doctors, and therefore has no unpleasant discussions with his neighbors about the relative merits of the different schools of medicine. If he has any predilections in the way of "pathies" we should say that he is a hydropath. While he is a great drinker, he is not at all convivial--he drinks only water, and takes that in solitary silence. He sows all his wild oats when he is very young, while he has the freedom to roam at will. He soon tires of this, however, for he selects the rock that is to be the foundation of his future home and there settles down for life, "wrapt in the solitude of his own originality." He is not troubled with wars or rumors of wars. His eyes are never startled or his nerves shaken by the scare headlines of yellow journalism. The one sensation of his life, if sensation he ever has, is when a great ugly creature of some Oriental clime comes down to his home and tears him away from his native rock, carries him to the surface, and there literally "squeezes the life out of him." He finally dies of the "grip," and here he sinks to the level of his more aristocratic neighbor.

But there is another side to our philosophy. If the sponge is exempt from all these ills that we have enumerated it is because he is incapable of suffering and is therefore incapable of enjoyment. Those beings that have the ability to suffer most have also the ability to enjoy most. The higher the type of civilization the greater possibilities it offers for real enjoyment--also for real misery. This being true, it should be the aim of highly civilized people to eliminate as far as possible those things that make for misery, and cultivate those things that make for happiness in the highest and best sense.

CHAPTER XXII.

WATER AND ICE.

We now have entered upon a subject that is of intense interest, studied from the standpoint of facts as they exist to-day and of history as we read it in the rocks and bowlders that we find distributed over the face of the earth.

The whole northern part of the United States extending to a point south of Cincinnati was at one time covered with a great ice-sheet, traces of which are plainly visible to anyone who has made anything of a study of this subject. The glaciers now to be seen in British Columbia and Alaska, great as they seem to one viewing them to-day, are by comparison with what once existed simply microscopic specks of ice. Glaciers, like rivers, flow by gravity, following the lowest bed and lines of least resistance; the difference being that in the one case the flow is rapid, while in the other it is scarcely visible, except by measurement from day to day. Before entering upon a description of the law that governs the flow of glaciers, let us stop and give a little study to the phenomena of water as exhibited when it is at the freezing point. Water is such a large factor in the make-up of our globe and the air that surrounds it that it becomes a very interesting and important study to anyone who wishes to understand the phenomena of nature that are closely related to it.

As all know, pure water is a compound of two gases, oxygen and hydrogen, combined in the proportion of two atoms of hydrogen and one of oxygen.

Let us now study this fluid in its relation to heat. The reader is referred to the chapters on heat in Vol. II., where it is stated that heat is a mode of motion. It is also stated that heat is a form of energy, and that energy is indestructible, that an unvarying amount of it exists in some form or another throughout the universe. It is not always manifested as heat or electricity, although both of these are always in evidence as active agents of force. Much of the energy is simply stored--all the time possessing the ability to do work or to be converted into any of its known forms, such as heat, light, electricity, or mechanical motion. A weight that is wound up has required a certain amount of energy to elevate it to the position that it occupies. While in its elevated position it possesses energy, although not active.

Energy in this form is called potential (possible) energy, and has the power to do work if released. Active energy is called kinetic (moving) energy, and the sum of these two energies is a constant quant.i.ty.

We will now study energy as it is related to water in the form of heat.

There is a kind of heat called "latent heat," which is not heat at all, but stored energy, waiting to be turned into heat, or light, or some other active form. Properly speaking, heat is a movement of the atoms of matter, the intensity of which is measurable in degrees, and called its temperature. To use the term latent heat as meaning concealed heat, which must reappear as heat, is a misnomer and is very misleading. If it is proper to call a wound-up spring or weight latent heat then its present use is a correct one. What was formerly termed latent heat is simply a form of potential energy. When sensible heat that is measurable, as temperature, disappears in the performance of some sort of work, especially in connection with certain phenomena relating to water, we call it--or rather miscall it--latent heat: but the phrase would better be "stored energy."

The action of water under heat is very peculiar, and in order to get a correct understanding of the phenomena exhibited in glacial action we also need to understand the phenomena of water at the freezing point. As is well known, fresh water freezes at 32 degrees Fahrenheit, and at the moment of freezing there is a sudden expansion to such an extent that a cubic foot of ice will occupy a much larger s.p.a.ce than it will in the form of water; and because it occupies so much larger s.p.a.ce it is lighter than the same bulk of water would be, and therefore it floats in water.

At the point of freezing, the thermometer if placed on the ice will register 32 degrees. If the ice is allowed to melt, the water at the moment of liquefaction would be found to register the same degree of temperature as the ice when first frozen. And yet there has been a vast expenditure of energy between the points of liquefaction and congelation, notwithstanding the temperature of ice may be lowered, after it is formed, many degrees, which is measurable by the thermometer. Suppose we take a piece of ice which is 10 degrees below the freezing point and insert in it a thermometer. If now we apply heat to this ice the thermometer will gradually rise until it reaches the melting point at 32 degrees Fahrenheit, where it will stand until all the ice is melted. The application of heat is going on steadily, but there are no indications of movement in the mercury until the last trace of ice with which it is in contact has been liquefied. After the ice is all melted, if the application of heat to the body of liquefied ice be continued, the column of mercury will resume its movement upward until it reaches the boiling point, where it is again arrested. And no matter how much heat is applied to the boiling water, if in an open vessel, the thermometer remains the same until all the water is evaporated. Here are two curious facts, and they are facts that, if we can master them, will serve as a key to the understanding of much that is mysterious in nature.

It will be our endeavor to give the reader a mental picture of what is taking place during the time the ice is melting and the thermometer is stationary. Do not suppose that you can understand this, even so far as it is understandable, by a casual reading without thought. No man was ever yet able to present a picture to the mind of another, however clearly and simply it may be done, unless that other mind is receptive.

When a photographer trains his camera upon an object, however intense the light may be and however clean-cut the picture that is thrown upon the plate in the camera, unless that plate is properly sensitized so that the picture may be impressed upon it, all of the other conditions are in vain. The reader is always a part of the book he is reading.

CHAPTER XXIII.

STORED ENERGY IN WATER.

In our last chapter we traced the upward movement in the mercury of the thermometer from 10 degrees below the freezing point up to the boiling point of water. We found that the thermometer was arrested at 32 degrees and remained stationary at that point until all the ice was melted, notwithstanding the fact that heat was being constantly applied. After the ice is all melted the mercury moves upward until it reaches the boiling point of water, where the movement is again arrested, and although the heat is being continuously applied, it remains stationary until all the water is evaporated. If we push the process still further, with a sufficient application of energy we can separate the vapor molecules into their original elements, oxygen and hydrogen.

Let us go back now to the freezing point of water and see what is becoming of the heat that is consumed in melting the cake of ice, and still does not produce any effect upon the mercury in the thermometer.

Sensible heat, as before stated, is a movement of the atoms of matter, and temperature, as it affects the thermometer, is a measure of the intensity of motion exhibited by these atoms.

In the experiment of the block of ice that in the beginning is 10 degrees below the freezing point, as shown by the thermometer, the molecules have a definite intensity of motion. The intensity of this motion increases when heat is applied until it reaches 32 degrees, when it remains stationary until all of the ice is melted. At this point there is a rearrangement of the molecules of water as it a.s.sumes the liquid state. To perform this rearrangement requires a certain amount of work done, which is a.n.a.logous to the winding up of a weight to a certain distance. There has been energy used in winding up the weight, but that energy now is not destroyed, nor still in the form of heat, but is in the potential state--ready to do some other kind of work. So, the heat that has been applied to the melting ice has been utilized during the process of its liquefaction in rearranging the water molecules and putting them in a state of strain, so to speak, like the weight that is wound up to a certain height. There is a certain amount of potential energy that is stored in the molecules of water that will be given up and become active energy in the form of heat, if the water is again frozen. To melt a cubic foot of ice requires as much heat as it would to raise a cubic foot of water 144 degrees Fahrenheit. But, as we have seen, while all of this energy is absorbed as heat, it is not lost as energy. It ceases to be kinetic or active and becomes potential energy.

This (let us repeat) has been called latent heat. The term grew out of the old idea that heat was a fluid and that when it became latent it hid itself away somewhere in the interatomic s.p.a.ces of matter and ceased to be longer sensible heat. It came into existence in the same manner and occupies the same place in the science of heat that the word "current"

does in the science of electricity: both of them are misnomers.

When the ice is all melted potential energy is no longer stored, but is manifested in the sensible heating of water, the degree of which is measurable by the thermometer, until it reaches the boiling point, where it is again arrested. All of the surplus heat above that temperature is consumed in rending the liquid water into moisture globules that float away into the air, each one of them charged with a store of potential energy. Let us follow this vapor spherule as it floats into the upper regions of the atmosphere. Myriads of its fellows travel with it until it reaches a point where condensation takes place, when it collapses and unites with other vapor particles to form water again. In doing this the heat that was expended upon it to disengage it (whether the heat was artificial or that of the sun's rays) now reappears either as sensible heat or as electricity, or both. And this is what is meant in meteorology by latent heat becoming sensible heat at the time of condensation; in fact, it is stored or "potential" energy becoming active or kinetic, and a.s.sumes the form of heat or electricity, as before stated. We have thus reviewed the matter of the foregoing chapter in order to follow the course of the stored energy from the melting of the ice to the vapor, and back again to water: to doubly impress the fact that the energy used was not consumed, but still exists and is ready for further work.

During the progress of a hailstorm, it has been stated, one of the factors that is active to produce this phenomenon is the intense ascensional force that is given to the moisture-laden air, caused by intense heat at the surface of the earth. This condition forces the moisture vapor to higher regions of the atmosphere than is the case with the ordinary thunderstorm. Another factor that is undoubtedly active in producing hail under these circ.u.mstances is that when condensation takes place in the higher regions, and is therefore more energetic on account of the intenser cold, the potential energy that is set free by the moisture spherules takes, in a larger degree, the form of electricity rather than heat, as is the case under more ordinary circ.u.mstances.

While in the end this electrical energy becomes active heat, it does not for the time being, and thus favors the ready congelation of the condensed moisture into hailstones. Hailstorms are always attended by incessant thunder and lightning, and this fact favors the theory advanced above.

It will be easily seen from a study of the foregoing what a wonderful factor evaporation (which is a product of the sun's rays) is, in the play of celestial dynamics. It ascends from the surface of the earth or ocean laden with a stored energy, the power of which no man can compute, and beside which gravitation is a mere point. In the upper regions of atmosphere this potential force under certain conditions is released and becomes an active factor, not only in the formation of cloud and the precipitation of rain, hail, and snow, but it disturbs the equilibrium of the air and sets that in motion.

Certain physicists deny that evaporation has anything to do with atmospheric electricity. They tell us that it is caused by the arrest of the energy of the sunbeam by the clouds and vapor in the upper atmosphere. We admit that a part of the energy is so arrested, and is stored, for the time, in moisture globules by a process of cloud evaporation to transparent vapor again. Yet this does not hinder the same process from going on at the surface of the earth wherever there is water or moisture. But they tell us that the electroscope does not show any signs of electrification in the evaporated moisture. Of course it does not. The electroscope is not made to detect the presence of energy except when set free as electricity.

A wound-up spring does not seem to be electrified, but if it is released the energy stored in it will be transformed into electricity if the conditions are right. Just so, the energy required to put the moisture spherule into a state of strain is latent until some power releases it, when it reappears as active energy of some form.

We have now followed the relation of heat to water from a point 10 degrees below freezing up to where it was forced into its original gases, oxygen and hydrogen. These gases have stored in them a wonderful amount of potential energy. When one pound of hydrogen and eight pounds of oxygen unite to form water the mechanical value of the energy given up at that time in the form of heat is represented by 47,000,000 pounds raised to one foot in height. And this is the measure of the energy that was put into nine pounds of water to force it from a state of vapor into its const.i.tuent gases. After the combination of the gases into a state of vapor the temperature sinks to that of boiling water. The amount of energy given up in condensing the nine pounds of vapor into nine pounds of water is equal to 6,720,000 foot-pounds. If this nine pounds of water is now cooled from the boiling point to 32 degrees Fahrenheit we come to the final fall, where the potential energy that is stored in the operation of melting ice is given up suddenly at the moment of freezing, which in nine pounds of water is 993,546 foot pounds.

Professor Tyndall, in speaking of the amount of energy that is given up between the points where the const.i.tuent gases unite to form nine pounds of water and the point where it congeals as ice, says: "Our nine pounds of water, at its origin and during its progress, falls down three precipices--the first fall is equivalent in energy to the descent of a ton weight down a precipice 22,320 feet high-over four miles; the second fall is equal to that of a ton down a precipice 2900 feet high, and the third is equal to a fall of a ton down a precipice 433 feet high. I have seen the wild stone avalanches of the Alps, which smoke and thunder down the declivities with a vehemence almost sufficient to stun the observer.

I have also seen snowflakes descending so softly as not to hurt the fragile spangles of which they are composed. Yet to produce from aqueous vapor a quant.i.ty which a child could carry of that tender material demands an exertion of energy competent to gather up the shattered blocks of the largest stone avalanche I have ever seen and pitch them to twice the height from which they fell."

When we contemplate the foregoing facts as related to so small an amount of water as nine pounds, and multiply this result by the amount of snow- and rainfall each year and the amount of ice that is congealed and again liquefied by the power of the sun's rays, we are appalled, and shrink from the task of attempting to reduce the amount of energy expended in a single year to measurable units.

Having considered water in its relation to heat in the preceding chapters, we will now take up the subject of water in its relation to ice and snowfall and the phenomena exhibited in ice rivers, commonly called glaciers.