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is a list of the substances which have been detected in adulterated tobacco. How many more may be in daily use for the purpose, who can tell? Is it surprising, therefore, that we should meet with manufactured tobacco possessing a thousand different flavours for which the chemistry of the natural leaf can in no way account?

Snuff has its own special adulterations, among which hel lebore, to provoke sneezing, is the most deadly.

As substitutes for, or admixtures with tobacco, the leaves of different species of rhubarb, large and small, are collected in Thibet and on the slopes of the Himalaya. The long leaves of a Tupistra, called Purphiok, which yield a sweet juice, are also gathered in Sikkim, chopped up and mixed with the tobacco for the hookah―(DR. HOOKER). Other substitutes for genuine tobacco have been adopted in other countries, either from poverty or from taste. As a substitute for tobacco snuff, the powdered rusty leaves of the Rhododendron campanulatum are used in India, and in the United States of North America the brown dust which adheres to the petioles of the kalmias and rhododendrons. All these plants possess narcotic qualities. The Otomacs, a tribe of dirt-eaters in South America, also make a kind of snuff from the powdered pods of the Acacia niopo. This snuff throws them into a state of intoxication bordering on madness, and which lasts for several days. While under its influence the cares and restraints of life are forgotten, and dreadful crimes are perpetrated.

7°. TOBACCO AN EXHAUSTING CROP.-One other point in the chemical history of tobacco, though not connected with its narcotic influence upon the system, it may be proper here to notice. I have elsewhere explained* that when vegetable substances are burned in the open air, they leave unconsumed a portion of mineral matter or ash. The leaves of plants

See THE PLANTS WE CULTIVATE

are especially rich in this incombustible ash, and those of tobacco are among the richest in this respect among culti-. vated leaves. The dried tobacco-leaf, when burned, yields from 19 to 28 per cent of ash; or, on an average, every four pounds of perfectly dry tobacco contain one pound of mineral or incombustible matter. It is this which forms the ashes of our tobacco pipes and the nozzles of our burning cigars.

It is unnecessary here to describe in detail the composi tion of this ash, but I may remind my reader that all the substances it contains have been derived from the soil on which the tobacco plant was grown, and that they belong to the class of bodies which are at once most necessary to vegetation and least abundant even in fertile soils. In proportion, therefore, to the weight of leaves gathered must have been the weight of these substances withdrawn from the soil. And as every ton of perfectly dry leaves carries off four to five hundred-weight of this mineral matter-as much as is contained in fourteen tons of the grain of wheat-it will readily appear, even to those who are least familiar with agricultural operations, that the growing of tobacco must be a very exhaustive kind of cultivation. He will see in this, also, one main reason why tobacco plantations have in past. times gradually become so exhausted as to be incapable, in many instances, of being longer cultivated with a profitwhy once fertile lands are now to be seen lying waste and deserted-and why the fortunes of tobacco planters, even in naturally favoured regions, have gradually declined with the failing fertility of their wearing-out plantations. Upon the Atlantic borders of the United States of America the bestknown modern instances of the effects of this exhausting tobacco-culture are to be found. It is one of the triumphs

of the chemistry of the present century, that it has ascer tained what the land loses by such imprudent treatment

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whatever crop is grown-what is the cause, therefore, of the barrenness which befalls it-by what new management its ancient fertility may be restored, and thus how new fortunes may be extracted from the same old soil.*

* See the Author's Lectures on Agricultural Chemistry and Geology, 2d edition, p. 644.

CHAPTER XVI.

THE NARCOTICS WE INDULGE IN.

THE HOP, AND ITS SUBSTITUTES.

The hop; whence derived; when brought to England.-Consumption in the United Kingdom.-Produce of Belgium.-Importance of the hop.-Beauty of the hop grounds. Management of the plant-Properties which recommend its use in beer. Varieties of the hop cultivated in England.-Qualities of the Farnham, Kent, North Clay, and Worcester hops.-Differences in estimation and flavour.Soils on which they grow.-Chemical constituents of the hop flower.-The oil of hops.-The aromatic resin.-The lupuline grains.-The bitter principle.-Physiological action of the hop.-Difference between ale and beer.-Bitter substances used instead of the hop.-Cocculus indicus.-Singular qualities of this berry; its use in adulterating beer.-Poisonous picrotoxin contained in it.-Narcotic substitutes for the hop in South America, in India, and in China.-The Heetoo, Keesho, and Taddo of Abyssinia.-The marsh ledum used in Northern Europe.— Use of the yarrow, clary, and saffron.

II. THE HOP-which may now be called the English narcotic-was introduced into this country at a comparatively recent period. It may have been employed in Germany in the times of the Roman writers, but was probably unknown to them. Its use, as an addition to malt liquor, appears to be of German origin. Hop gardens, by the name of Humolariæ, are spoken of in documents of the early part of the ninth century, and frequently in those of the

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thirteenth century. In the breweries of the Netherlands the hop seems to have been introduced about the beginning of the fourteenth century. From the Low Countries, or, as some say, from Artois, which borders upon them, it was brought to England in the reign of Henry VIII., some time after his expedition against Tournay, and about the year 1524. In the twenty-second year of his reign (1530), that monarch, in an order respecting the servants of his household, forbad sulphur and hops to be used by the brewers. Three quarters of a century later (1603) the introduction of spoilt and adulterated hops was forbidden by James I. under severe penalties. This appears to show that, though considerable attention is known to have been already given to the cultivation of the hop in England, a large part of the hops supplied to the home market was still brought from abroad.

*

10. CONSUMPTION OF THE HOP.-At present, the hops consumed in the United Kingdom are almost entirely of home growth, and the consumption is very great. For the last four years the quantities retained for home consumption, and the amount of duty † paid into the revenue, amounted to

This average is supposed to represent as large a quantity of hops as is grown in all the world besides. How different a taste does this large consumption argue now from what

This probably refers to the practice, which still prevails, of whitening or bleaching hops with fumes of sulphur, and which may not then have been so skilfully con ducted as it is now.

The duty is 188. 8d. the cwt., and five per cent additional.