COFFEE.

BOTANICAL ORIGIN.-The coffee tree, Caffea arabica, belongs to the natural order Cinchonaca. It is an evergreen, with smooth, shining, oblong and leathery leaves. It was originally a native of Abyssinia and Arabia, but has been naturalised in most of the tropical countries colonised by Europeans. In its natural state it attains to a height ranging from 15 to 20 feet, but in cultivation it is pruned so as to remain about 6 feet high to facilitate the gathering of the berries. The coffee tree continues flowering for eight months in the year, and during the whole of that period fruit of very unequal ripeness is found upon its branches. Three gatherings of the berries are made in the course of the year.

Description. The ripe berry is about the size and shape of a small cherry, and of a dark scarlet colour. In each berry there are usually two beans placed face to face, and enclosed in a hard coriaceous membrane, surrounded, when fresh, by a fleshy shell or pericarp, which, when dry, becomes hard and brittle. The berries, after being dried by the rays of the sun, are passed between rollers to remove the dried pulpy matter and the coriaceous membrane. They are then sorted according to size preparatory to roasting. The tissues enclosing the bean are generally distinguished as the husk, the parchment, and the skin. The first two are very rarely if ever met with in commerce, but

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the skin, which is more or less entangled in the folds of the longitudinal furrow on the flat side of the bean, is present in every sample of commercial coffee.

History. It is affirmed that the use of coffee has been common in Abyssinia from time immemorial; but the early days of coffee drinking are involved in considerable obscurity. The employment of coffee as a beverage was first commenced in England about the middle of the seventeenth century, when a coffee-shop was opened in the city of London, and similar establishments gradually sprang up, notwithstanding the heavy tax placed on coffee, and the disfavour with which they were for a long time looked upon by the constituted authorities.

During the year 1699, the consumption of coffee in the United Kingdom amounted to 100 tons, of which 70 tons were consumed in England. In the year 1808, the consumption amounted to 477 tons, and a reduction of duty in that year was followed by an immediate increase in consumption, from 1,069,696 lbs. to 9,251,837 lbs. In 1825 another reduction of the duty took place, after which the consumption still further increased, until, in 1847, the maximum of 37,441,373 lbs. was reached. Since that date the use of coffee has greatly declined, and in 1874 the consumption was 31,859,408 lbs., whilst in 1880 it amounted to 32,480,000 lbs. The falling off which has taken place since 1847 is supposed to be due partly to an extended use of tea, and partly to the introduction of coffee substitutes.

The cultivation of the coffee plant began to extend towards the end of the seventeenth century, and soon afterwards its growth was successfully carried on in various countries possessing tropical climates, such as Java, Ceylon, Jamaica, and Brazil. The cultivation of coffee in Brazil is now very considerable, but that produced in Java and Ceylon is of superior quality, though the Mocha coffee is the finest of all. The quantity of "Mocha" which finds its way into Europe from Arabia is said to be comparatively small, and

we are now indebted chiefly to India for our supply of this description of coffee.

The effect of coffee on the human system is to counteract the tendency to sleep; and it is almost certain that it was this property which originally led to its use as a beverage. It also excites the nervous system, and when taken in excess produces contractions and tremors of the muscles, and a feeling of buoyancy and exhilaration somewhat similar to that produced by alcohol, but does not end with depression or collapse.

CHEMICAL COMPOSITION.

The principal organic substances composing the raw coffee beans are caffeine, fat, caffeic acid, gum, saccharine matter, legumin, and cellulose. These substances are also found in the roasted beans, though modified in some degree by the roasting process. By torrefaction the woody tissue of the fresh bean, which is hard and horny, undergoes a considerable change, and becomes friable, and the difficulty of pulverising and exhausting it by water is greatly diminished.

Coffee has, like tea, been the subject of numerous investigations, but the following analysis by Payen is most frequently quoted :

We have obtained the following results from two samples of coffee, both in the raw and roasted condition :

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Caffeine, C, H, N, O,.-This, from its dietetic properties, is one of the most valuable constituents of coffee, and is identical with the alkaloid found in tea, and described under the name of theine. Caffeine was discovered in coffee by Runge, in the year 1820; by Oudry, in tea in 1827; by Martin, in guarana, in 1840; and by Stenhouse, in Paullinia, in 1843. Its chemical constitution was settled by Jobst and Mulder.

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Fat.-The fatty portion of the coffee consists of a mixture of several fats, some of which have the consistence of an oil. become altered to some extent in the process of roasting, and a portion of the volatile fatty acid is set free, and changed in character by the heat. The quantity of fat in the raw coffee is also more or less affected by the roasting, but the extent to which this takes place depends upon the degree to which the torrefaction

is carried. We have found that in ordinary commercial samples of roasted coffee the loss of fat amounts to about 1 per cent., but the loss may be greater than this in cases in which the coffee is subjected to a more than ordinary degree of roasting.

Caffeone. This remarkable and characteristic body is a product of the roasting of coffee. It consists of an oil which gives the coffee aroma, and which is doubtless a mixture of the altered volatile oil and other products probably obtained from several of the constituents of the raw coffee by the action of heat. Caffeone, which is the aromatic principle of coffee, can be partially separated by distillation, when it is found as a brown oil heavier than water.

Caffeic Acid. This is also known by the names of caffeotannic acid and chlorogenic acid, and is present in coffee to the extent of from 3 to 5 per cent. It is obtained as a yellowish mass, and is more easily soluble in water than in alcohol. When heated it emits the peculiar odour of coffee, and from this it is thought that this acid plays an important part in developing the flavour found in the roasted beans. An infusion of raw coffee, when heated with alkalis, gradually acquires a bright green colour, which is supposed to be produced by the change of caffeic acid into viridic acid. Caffeic acid, distilled with peroxide of manganese and sulphuric acid, yields quinone.

Sugar. The raw coffee beans contain from 5'70 to 7.70 per cent. of a fermentable sugar. When, however, the sugar extracted from the beans is boiled for a few minutes with a little dilute sulphuric acid, the amount shown by an alkaline cupric solution is equivalent to from 8.9 to 9'55 per cent.

The sugar in coffee, unlike cane-sugar in sweet roots, becomes almost wholly converted into caramel in the process of roasting; but, so far as we are aware, no satisfactory explanation has been given of this peculiarity.

It has been suggested that a portion of the sugar exists in the form of a conjugate combination, like the sugar in salicin and