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 vegetoanimal 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 torule 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.

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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 be tween 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,

G

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 otherwise applying chemical processes to practical purposes.

To the chemistry of the century the world is indebted for those devices and processes for the utilisation and manufacture of many useful products from the liquids and oils, sugar from cane and beets, revivifying bone-black, centrifugal machinery for refining sugar, in defecating it by chemicals and heat,

in evaporating it in pans, in separating starch and converting it into glucose, etc.

a waste.

Oils and Fats.-Up to within this century the vast amount of cotton seed produced with that crop was Then by the process, first of steaming the seed and expressing the oil, now by the process of extraction by the aid of volatile solvents, and casting off the solvents by distillation, an immensely valuable product has been obtained.

The utilising of oils in the manufacture of oilcloth and linoleum and rubber, has become of great commercial value. Formerly sulphur was the vulcanising agent, now chloride of sulphur has been substituted for pure sulphur.

Steam and the distillation processes have been applied with great success to the making of glycerine from fat and from soap underlye and in extracting fat from various waste products.

Bleaching and Dyeing. Of course these arts are very old, but the old methods would not be recognised in the modern processes; and those who lived before the century knew nothing of the magnificent colours, and certain essences, and sweet savours that can be obtained from the black, hand-soiling pieces of coal. In the making of illuminating gas, itself a finished chemical product of the century, a vast amount of once wasted products, especially coal tar, are now extensively used; and from coal tar and the residuum of petroleum oils, now come those splendid aniline dyes which have produced such a revolution in the world of colours. The saturation of sand by a dye and its application to fabrics by an air blast; the circulation of the fluid colors, or of fluids for bleaching or drying, or oxidising, through perforated cylinders or cops on which the cloths are

wound; devices for the running of skeins through dyes, the great improvements in carbon dyes and kindred colours, the processes of making the colours on the fibre, and the perfumes made by the synthetic processes, are among the inventions in this field.

The space that a list of the new chemical products of this age and their description would fill, has already been indicated by reference to the great dictionary of Watts. Some of the electro-chemical products will be hereinafter referred to in the Chapter on Electricity, and the chemistry of Metallurgy will be treated under the latter topic.

Electro-chemical Methods.-Space will only permit it to be said that these methods are now employed in the production of a large number of elements, by means of which very many of them which were be fore mere laboratory specimens, have now become cheap and useful servants of mankind in a hundred different ways; such as aluminium, that light and non-corrosive metal, reduced from many dollars an ounce a generation ago, to 30 and 40 cents a pound now; carborundum, largely superseding emery and diamond dust as an abradant; artificial diamonds; calcium carbide, from which the new illuminating acetylene gas is made; disinfectants of many kinds; pigments, chromium, manganese, and chlorates by the thousand tons. The most useful new chemical processes are those used in purifying water sewage, and milk; in electroplating metals and other substances, in the application of chemicals to the fine arts, in extracting grease from wool, and the making of many useful products from the waste materials of the dumps and garbage banks.

Medicines and Surgery.-One hundred years ago, the practice of medicine was, in the main, empirical.