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of being converted one into another, and the indestructibility of matter, of which force is but another name.
The first demonstrations as to the nature of heat were given by the American Count Rumford, and then by Sir Humphry Davy, just at the close of the 18th century, and then followed in this the brilliant labours and discoveries of Mayer and Helmholtz of Germany, Colding of Denmark, and Joule, Grove, Faraday, Sir William Thomson of England, of Henry, Le Conte and Martin of America, as to the correlation and convertibility of all the forces.
The French revolution, and the Napoleonic wars, isolating France and exhausting its resources, its chemists were appealed to devote their genius and researches to practical things; to the munitions of war, the rejuvenation of the soil, the growing of new crops, like the sugar beet, and new manufacturing products.
Lavoisier had laid deep and broad in France the foundations of chemistry, and given the science nomenclature that lasted a century. So that the succeeding great teachers, Berthollet, Guyton, Fourcroy and their associates, and the institutions of instruction in the sciences fostered by them, and inspired in that direction by Napoleon, bent their energies in material directions, and a tremendous impulse was thus given to the practical application of chemistry to the arts and manufactures of the century.
The same spirit, to a less extent, however, manifested itself in England, and as early as 1802 we find Sir Humphry Davy beginning his celebrated lectures on the Elements of Agricultural Chemistry before a board of agriculture, a work that has passed through many editions in almost every modern language.
When the fact is recalled that agricultural chemistry embraces the entire natural science of vegetable and animal production, and includes, besides, much of physics, meteorology and geology, the extent and importance of the subject may be appreciated; and yet such appreciation was not manifested in a practical manner until the 19th century. It was only toward the end of the 18th century that the vague and ancient notions that air, water, oil and salt formed the nutrition of plants, began to be modified. Davy recognized and explained the beneficial fertilizing effects of ammonia, and analysed and explained numerous fertilizers, including guano. It is due to his discoveries and publications, combined with those of the eminent men on the continent, above referred to, that agricultural chemistry arose to the dignity of a science. The most brilliant, eloquent and devoted apostle of that science who followed Davy was Justus von Liebig of Germany, who was born in Darmstadt in 1803, the year after Davy commenced his lectures in England. It was in response to the British Association for the Advancement of Science that he gave to the world his great publications on Chemistry in its application to Agriculture, Commerce, Physiology, and Pathology, from which great practical good resulted the world over. One of his favorite subjects was that of fermentation, and this calls up the exceedingly interesting discoveries in the nature of alcohol, yeast, mould – aging malt, wines and beer – and their accompanying beneficial results.
In one of Huxley's charming lectures – such as he delighted to give before a popular audience – delivered in 1871, at Manchester, on the subject of "Yeast," he tells how any liquid containing sugar, such as a mixture of honey and water, if left to itself undergoes the peculiar change we know as fermentation, and in the process the scum, or thicker muddy part that forms on top, becomes yeast, carbonic acid gas escapes in bubbles from the liquid, and the liquid itself becomes spirits of wine or alcohol. "Alcohol" was a term used until the 17th century to designate a very fine subtle powder, and then became the name of the subtle spirit arising from fermentation. It was Leeuwenhoek of Holland who, two hundred years ago, by the use of a fine microscope he invented, first discovered that the muddy scum was a substance made up of an enormous multitude of very minute grains floating separately, and in lumps and in heaps, in the liquid. Then, in the next century the Frenchman, Cagniard de la Tour, discovered that these bodies grew to a certain size and then budded, and from the buds the plant multiplied; and thus that this yeast was a mass of living plants, which received in science the name of "torula," that the yeast plant was a kind of fungus or mould, growing and multiplying. Then came Fabroni, the French chemist, at the end of the 18th century, who discovered that the yeast plant was of bag-like form, or a cell of woody matter, and that the cell contained a substance composed of carbon, hydrogen, oxygen and nitrogen. This was a vegeto-animal substance, having peculiarities of "animal products."
Then came the great chemists of the 19th century, with their delicate methods of analysis, and decided that this plant in its chief part was identical with that element which forms the chief part of our own blood. That it was protein, a substance which forms the foundation of every animal organism. All agreed that it was the yeast plant that fermented or broke up the sugar element, and produced the alcohol. Helmholtz demonstrated that it was the minute particles of the solid part of the plant that produced the fermentation, and that such particles must be growing or alive, to produce it. From whence sprang this wonderful plant – part vegetable, part animal? By a long series of experiments it was found that if substances which could be fermented were kept entirely closed to the outer air, no plant would form and no fermentation take place. It was concluded then, and so ascertained, that the torulae in the plant proceeded from the torulae in the atmosphere, from "gay motes that people the sunbeams." Concerning just how the torulae broke up or fermented the sugar, great chemists have differed.
After the discovery that the yeast was a plant having cells formed of the pure matter of wood, and containing a semi-fluid mass identical with the composition which constitutes the flesh of animals, came the further discovery that all plants, high and low, are made up of the same kind of cells, and their contents. Then this remarkable result came out, that however much a plant may otherwise differ from an animal, yet, in essential constituents the cellular constructure of animal and plant is the same. To this substance of energy and life, common in the minute plant cell and the animal cell, the German botanist, Hugo von Mohl, about fifty years ago gave the name "protoplasm." Then came this astounding conclusion, that this protoplasm being common to both plant and animal life, the essential difference consisted only in the manner in which the cells are built up and are modified in the building.
And from that part of these great discoveries which revealed the fact that the sugary element was infected, as it were, from the germs of the air, producing fermentation and its results, arose that remarkable theory of many diseases known as the "germ theory." And, as it was found in the yeast plant that only the solid part or particle of the plant germinated fermentation and reaction, so, too, it has been found by the germ theory that only the solid particle of the contagious matter can germinate or grow the disease.
In this unfolding of the wonders of chemistry in the nineteenth century, the old empirical walls between forces and organisms, and organic and inorganic chemistry, are breaking down, and celestial and terrestrial bodies and vapours, living beings, and growing plants are discovered to be the evolution of one all-pervading essence and force. One is reminded of the lines of Tennyson:
"Large elements in order brought
And tracts of calm from tempest made,
And world fluctuation swayed
In vassal tides that followed thought.
One God, one law, one element,
And one far-off divine event
To which the whole creation moves."
In the class of alcohol and in the field of yeast, the work of Pasteur, begun in France, has been followed by improvements in methods for selecting proper ferments and excluding improper ones, and in improved processes for aging and preserving alcoholic liquors by destroying deleterious ferments. Takamine, in using as ferment, koji, motu and moyashi, different forms of mould, and proposing to do entirely away with malt in the manufacture of beer and whiskey, has made a noteworthy departure. Manufacturing of malt by the pneumatic process, and stirring malt during germination, are among the improvements.
Carbonating.– The injecting of carbonic acid gas into various waters to render them wholesome, and also into beers and wines during fermentation, and to save delay and prevent impurities, are decided improvements.
The immense improvements and discoveries in the character of soils and fertilisers have already been alluded to. Hundreds of instruments have been invented for measuring, analysing, weighing, separating, volatilising and