ENERGY.

New Zealand Herald, Volume LVI, Issue 17234, 9 August 1919, Page 1 (Supplement)

ENERGY.

1 BY NATUHAXiXST.

THE ULTIMATE SOURCES.

No. n. Most of, the immediate sources from, which man derives energy are obvious enough. He may utilise the vast supplies that have been locked up in the carbonaceous matter of the earth during long ages. He may harness the power of the wind, and from the water sa it escapes om the artificial dam or hurls its mass with thunder and spray he may desire power for all time. But how does the wind, or the running water, or the coal ot the earth happen to possess# energy at all? It may; be answered at. once that the son is the ultimate source from which, no matter how diverse their channels may be, ail these streams of energy originally flow. It may not be at first 'apparent how this comes about. Animal Energy. Let us first consider how energy is produced in the animal body. The food which the animal consumes belongs to those three classes of organic compounds termed proteins, carbohydrates and fats. This carbonaceous food, having been considerably altered in the process of digestion, but nevertheless retaining its carbon, is eventually elaborated to form part of the living substance of the cells. Protoplasam, then, as this is called, is a carbon compound, though of an exceedingly complex: nature. Mow the blood, passing in & constant stream through the clustered capillary vessels of the lungs, is separated but by thin membranous walls bora the air ' which distends the air sacs. Oxygen from the air diffuses through these thin walls and enters the' blood, where it readily combines with the substance haemoglobin of the swd blood corpusclesIt is the oxy-haemoglobin so formed which imparts the bright, scarlet colour to pure, arterial or oxygenated blood. By the contractions of the heart the oxygenated blood is pumped through an intricate syst em oframifying blood vessels, so that there is not a single tissue, or a, single eel' that is not brought into intimate contact wih he oxygen-carrying blood stream. Remembering the ease with which many compounds of carbon are oxidised, it is but to be expected that the oxygen, leaving the haemoglobin with which it is loosely combined, should enter into combination v?th the carbon of the protoplasm. This, in effect, is .actually what does happen. The protoplasm is oxidised, and so broken into simpler compounds, many of which are excreted, while, at the same time, in consequence of this rhpmtr-?.! reaction, heat is produced.

The oxidation of carbon in the tissues of the animal body is essentially similar to other examples of combustion. It is, of course, a process of slow combustion comparable with the rusting or iron rather than with tae union of phosphorus and oxygen, which takes place very rapidly with the emission of flame, But, although no flame is produced in this case, it is a matter of the greatest significance that, in consequence of the alow combustion of the matter of its cells, heat is produced in the animal body, Heat energy- thus originated i* transformed through the muscles into mechanical energy. Muscular -movement is com raunicated to certain of the, bones which move in much the same way that levers arc moved in a machine. . Hence is the animal body rendered capable of doing work. There is much truth, it seems, in the statement that the animal body is "a nhysico-chemical engine with the power bf working." fuel fox the Engine. *• The necessity for a constant supply of fcoa from which fresh protoplasm may be elaborated is obvious. ; Proteins, carbohydrates, and fats, the three - classes of compounds to which animal foods belong, are all manufactured in the first instance by plants.* Animal life, then, depends directly on plant life. But it may be contended some animals feed upon the flesh of others. True, but those others derived their /nourishment from , the vegetable world. How, then, does the plant secure and store these carbonaceous substances so valuable as food for the animal creation, or, as we may Bay, so essential as fuel for the living machine I The Plant At Work. Whenever combustion takes place, whether in the animal body or in the slow decay of animal matter, whether in the burning of fuel in a furnace or of a candle in air, the gas carbon-di-oxide is formed by the union of the carbon of the combustible material with oxygen. Thus ; traces of carbon-dioxide are ever present in the atmosphere- Plants take in atraopheric air through the numerous stomata or breathing pores with which their leaves are furnished. The carbon-di-oxide that the inspired air contains is bioken up in the plant's body, and while \ the oxygen is liberated the carbon is retained. The carbon thus retained, together with water and- various inorganic salts which the plant derives from the soil through its roots, is. elaborated by the plant to form complex organic compounds, most of -which are the very materials which the animal requires for food. The Plant's Energy The process by which the plan* elaborates carbon compounds goes on only in the presence of sunlight. Hence it is wow termed the process of photosynthesis. But photosynthesis involves work done by the plant. Whence comes the energy that enables the plant to do this work! The fact that the process depends on the presence of sunlight for its accomplishment provides a' clue. The plant utilises the light energy radiated from the sun. The sun's energy is absorbed by a special substance which plants alone possess. This is chlorophyll, the green colouring matter of plants. It occurs in grains, assembled in clusters known as chloro--1 lasts. These the miscroscope reveals distributed throughout the substance ofl tht green plant cell.

Solar Energy Stored By Plants. We have seen that the plant, by means of its chlorophyll, directly utilises the radiant light energy of the sun to bniliT up certain carbon compounds. These substances taken in by- animals as food are built up to form the protoplasm of the ti«-ues. Subsequently the oxidation of protoplasm gives rise to heat energy, which is transformed into mechanical energy by the animal body thus rendered active. It is clear, men, that the energy displayed by the whole living world, both animal and -vegetable, is derived ultimately from solar sources. It •will be remembered that the wood we burn as a fuel is a vegetable product. So it, peat, and so, too, is coal. They both represent the changed remains of vast accumulations of vegetable matter which grew upon the earth long- ages' ago. So, toe, the mineral oils which the earth yields are supposed to be products of accumulations of animal and vegetable matter of marine origin, reduced to their present form by the continued action of neat and great pressure throughout the sees of geological time. So, the fuels which feed our furnaces to-day to liberate the vast stream of energy necessary for industrial purposes are all products of the ancient organic life of the earth. The potential energy of all such fuels has been stored by the age-long activity of countless generations of plants, which, like their modern descendents, absorbed the radiant energy of the solar light.