of course a corresponding pressure on the other side to counterpoise it; so that there is suspended on the gudgeon and moving freely upon it nearly 200 tons. The whole reflects great credit on Mr. Arthur Woolf, by whom these engines have been erected.-Annals of Philosophy.

On the Chemical, Economical, and Medical Virtues of the Common Hop. By A. W. IVES, M. D. of New York.*

THE hop or humulus is a hardy perennial plant which grows spontaneously in the Northern parts of Europe and America. It belongs to the class Dioecia and order Pentandria of Linnæus; the plant which bears the male flower is not cultivated, and is called the Wild-hop. The common domestic hop, which is the female plant, was the subject of Dr. Ives's investigation.

A quantity of hops was procured, which had been kept for domestic purposes in a small bag for three years. When they were taken from the bag there remained about two ounces of an impalpable yellow powder,' which, by sifting, was rendered perfectly pure. This substance has probably been observed by most persons acquainted with the hop; and Dr. Ives suspects that it has been generally mistaken for pollen, but it is peculiar to the female plant, and is, probably, secreted by the nectaria: Dr. Ives calls it lupulin.

From various experiments on lupulin, Dr. Ives infers that it contains a very subtle aroma, which is yielded to water and to alcohol, and which is rapidly dissipated

* Abridged from an American Scientific Journal; the paper may be seen at large in the Annals of Philosophy, for March, 1821.

by a high heat; that no essential oil can be detected by distillation in any portion of the hop; that lupulin contains an extractive matter, which is soluble only in water; that it contains tannin, gallic acid, and a bitter principle which are soluble in water and in alcohol; that it contains resin which is dissolved by alcohol and by ether; and wax which is soluble only in alkalies, and in boiling ether; that it contains neither mucilage, gum, nor resin; that the aromatic and bitter properties of lupulin are more readily and completely imbibed by alcohol than water; and much sooner by both when they are hot, than when they are cold; that about five eighths of the whole substance is soluble in water, alcohol and ether; there being about three eights of it vegetable fibrous matter. These proximate principles exist in very nearly the following proportions. In two drachms or 120 grains of lupulin, there was of

A woody fibrous substance, or lignin - 46

Two drachms of the leaves, (by leaves are meant the calices which form the flower, or that part of the hop commonly used in brewing) from which all the lupulin had been separated, were digested 12 hours in six ounces of boiling water. The infusion was bitter, and exceedingly unpleasant to the taste; it possessed none of the aromatic flavour and peculiar bitter of the lupulin. When filtered and evaporated, it yielded five grains of nauseous extract. The same leaves were again digested in six ounces of proof spirit: after 12 hours the infusion

was filtered, and in evaporation yielded five grains of extract similar to the last. The same leaves were digested 24 hours in alcohol; the infusion manifested none of the sensible properties of the hop. It gave, by evaporation, four grains of extract. The taste of none of the extractive matter obtained from the leaves was sufficiently characteristic of the hop, to designate that it was obtained from that article.

From these and other similar experiments, Dr. Ives thinks it is conclusively proved, that the virtue of the hop resides exclusively in the lupulin; that the leaves contain a nauseous extractive matter, which is imparted to water and to alcohol, and which, instead of adding to the bitter and aromatic flavour of the lupulin, partially neutralizes or destroys it.

The obvious inference from these results was, that the lupulin was the only part of the hop essential to economical purposes; an inference so little anticipated, that it became an important subject of inquiry, whether that part of the plant was duly estimated by practical brewers; whether it had been regarded by authors as preferable to the leaves; and if so, what impediment or what consideration prevented its being separated from the chaff.

From these experiments, Dr. IVES was induced to ascertain the proportion of lupulin in the merchantable hop; and also, whether it could be completely and readily separated from the leaves. Six pounds of pressed hops were taken from the centre of a bag containing some hundred pounds, and exposed to heat till perfectly dry. They were then put into a light bag, and by threshing, rubbing, and sifting, 14 ounces of this fine powder were separated in a short time, and with very little labour; and though the quantity thus obtained was surprisingly great, there was obviously a considerable

portion remaining, which could not be easily separated from the chaff. If, therefore, the hops were gathered when the lupulin existed in the greatest abundance, and instead of being pressed and packed, were exposed to the sun till perfectly dry, there is little doubt but six pounds would yield a pound of the powder in question.

Two barrels of beer were made late in the spring, in which nine ounces of the lupulin were substituted for five pounds of hops. The result confirmed the most sanguine expectation. Though the quantity of lupulin was less than what usually enters into the same quantity of wort; and though the weather during the month of June was unusually warm, and therefore unfavourable to its preservation, still the beer, which is now five weeks old, is very fine, pleasantly aromatic and bitter, and in a perfect state of preservation.

To ascertain the preservative property of the lupulin by a more direct experiment, equal quantities of the beer were put into separate vials, and exposed, unstopped, to the sun. To the beer in one vial was added a scruple of lupulin. The beer to which none was added, became mouldy and sour in ten days; the other was unchanged at the expiration of fifteen days.

These experiments and their results are highly deserving the public attention.

As a medicine, either the tincture or infusion of lupulin may be given, according to circumstances, with more advantage than the hop in the way it is at present ordered. Dr. IVES recommends the saturated alcoholic tincture of lupulin in doses of from 40 to 80 drops, to produce sleep, which it will do, he says, with as much certainty as opium, in cases of loug watching from nervous irritability; but the same cannot be said of its

efficacy in relieving pain. As a stómachic, a trial of lupulin is certainly desirable to be made.

On Magnetism.

IT gives us much pleasure to observe the zeal and assiduity which has been lately manifested among philosophers relative to this subject. To the researches of M. OERSTED, Sir HUMPHREY DAVY, the French Savans, and Mr. BARLOW, a communication from whom on this subject enriches our present number, and Mr. LECOUNT, we desire to call our readers' attention to the important discovery of the North-west Magnetic Pole, by the last voyage of Capt. Parry. By the accounts in the public journals, it appears that on the 4th of September, 1819, the expedition reached Copper-mine Roads. Previous to this the variation of the compass had changed from 124° W. to 166° E., the ships having, as was supposed, crossed the magnetic meridian in about 100° W. As the compasses there showed the ship's head to be N. E. and on all tacks, they judged themselves at no great distance from the magnetic pole. The compasses had indeed been perfectly useless from the time of their passing Lancaster Sound, which obliged them to steer by the sun when it was out, and how they could when it was not; often lying-to when the fog was thick. A paper by Colonel MACDONALD has also been published in some of the journals on this subject, which is deserving of attention.

It appears that in the year 1576, the variation of the needle was at London 11° 15' east; that it diminished graVOL. II.

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