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Pliny, as has been ingeniously demonstrated by Salmasius in opposition to Scaliger, clearly describes tabasheer of the Bamboo under the name of sugar, when he speaks of it as “ a honey formed in canes, white like gum, crumbling between the teeth, found in lumps about the size of a filbert, and only used medicinally." Yet it is manifest from the verses of Varro, quoted by Isidorus, from passages of Theophrastus, Lucan, Solinus, and especially Strabo, on the authority of Eratosthenes, that the ancients had derived some notion of our sugar from the East In• dies, and affirmed that it was obtained from canes without the assistance of the bee. But then they believed that a liquid of the sweetness of honey was expressed from the roots of the large kind of canes, confounding the root with the haulm, and the humble sugar-cane (SACCHARUM officinale) with the Bamboo, “ a joint of wbich, when split asunder, they described as large enough to form a navigable bark.” Others among them, as Seneca, Dioscorides, and Alexander Aphrodisæus, believed true sugar to be the morning dews of the canes, collected on the foliage of the plant. It is certain that the sugar-cane is indigenous in the neighbourhood of Almangar, in the East Indies, on the bauks of the Euphrates, and at Siraf; but I suspect that in that part of Asia which was frequented by the Greeks, the plant was only expressed for the purpose of procuring a beverage for iminediate use, and that the juice never could have been exported, owing to its tendency to ferment. So that I conclude, that hard sugar was unknown to the ancients,* and that when they speak of a solid sugar, they mean tabasheer or schar. kara of Bamboo.

It may be hardly thought necessary that we should mention in this place, that before America was discovered by the Spaniards,

* The art of making sugar from the cane was not mentioned by any writers until the fifth century, and, as the learned Sprangeli has firsi shewn, Moses Chorenensis, in describing the beauties of the province of Chorasan, mentions the valley of Gundi-Saporem “as a place where the precious sugar was made." I have proved in another place, that the manufacture of sugar was of the highest antiquity in China.

the inhabitants of that continent and the adjacent islands, were entirely unacquainted either with the sugar-canes, or with any of our corn-plants, (which last are indigenous of the country between the Kur and the Terek, in Persia and Armenia), or with rice. The Spanish writers on the subject of America, give the name of small rice (Oryza parva) to the CHENOPODIUM Quinou, which is common in Santa Fe de Bagotá, and in the kingdom of Quito, in the same way as the Anglo-Americans did that of Canada rice to a species of ZIZANIA. Turkey corn, (Zea Mays), like many of the plants which have been in general cultivation from remote periods, is not found growing wild in any part of America. We have to lament that travellers have not made us correctlyacquainted with the characters of the plants mentioned cursorily by Molina, in his history of Chili, under the names of Secale Magu and Hordeum Tuca, of which the Araucanos sormerly made a bread called couque. We know from Cortes that the Agave and Turkey corn afforded the Americans a honey independently of the bee, and that he saw it in market at Tenochlitl.

Art. V. Description of an Aerometer, for making the

necessary Corrections in Pneumatic Experiments, for reducing the Volumes of the Gases to a given Standard.

By MARSHALL HALL, M. D. &c. In experiments on the Gases, it is generally necessary to make a correction, in order to ascertain their mean bulk; for changes in the temperature of the atmosphere, in the barometrical pressure, in the external and internal heights of the fluid of the pneumatic trough; and, when this trough contains water, for the elevation or precipitation of aqueous vapour, from these causes. And, in delicate experiments, it is frequently desirable to ascertain whether any slight change in the volume, or apparent quantity of the gas, be owing exclusively to the agency of an external cause, or whether there be an absorption, or evolution of gas, by the materials subjected to the experiment.

To obtain these corrections, it is usually proposed to make

three or four separate calculations; and a formula for each of these is given in the elementary works on Chemistry. It is the object, however, of the present communication, to describe an instrument, by the aid of which the necessity for these calculations may be superseded. This instrument, which may be termed an Aërometer, consists of a bulb of glass, four cubic inches and a half in capacity, attached to a long tube, whose capacity is one cubic inch. This tube is inserted into another tube, of nearly equal length, and supported on a stand, in the manner represented in the annexed figure.

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The first tube admits of being sustained within the second, at any given height, by means of a spring, by which it is embraced, and which is fixed to the upper part of the external tube. Five cubic inches of atmospheric air, under a medium pressure, and in a medium temperature, are to be introduced into the bulb and tube, of the latter of which it will occupy one-half; the other half of this tube, and part of the tube into which it is inserted, are to be occupied by the fluid of the pneumatic trough, whether water or mercury. The point of the.tube, at which the air and fluid meet, is to be marked by the figure 5, denoting five cubic inches by measure ; the upper and lower halves of the tube arc each to be divided into five parts, representing tenths of a cubic inch. The external tube is to be marked by a scale of inches, like the common carpenter's rule.

It is manifest that the condition of the gases, made the subject of experiment, as affected by external temperature and pressure, and by the formation or precipitation of aqueous vapour, when water is contained in the pneumatic trough, will be precisely similar to that of the air contained in the Aërometer. Now, if the height of the fluid of the pneumatic trough be different from that of the fluid within the jar, this difference is to be measured, and a precisely similar difference is to be induced in the external and internal heights of the fluid of the Aërometer, by raising or depressing the tube of the Aërometer, in the tube containing it.

The gases made the subject of experiment, and the air contained in the aërometer, are now placed, in every point of view, in similar circumstances, and it is only necessary to compare them. If the volume of the air of the aërometer be increased or diminished, that of the gases subjected to experiment may be concluded to be affected in a similar and proportionate manner. The air of the aërometer becomes, therefore, the point of comparison, and the measure of the gases in the pneumatic jar. Let a be the volume of the air con. tained in the aërometer, and b, that of the gases, on which the experiment is made : then

a: 5;: b the real volume of the gases, under a medium pressure, and in a medium temperature.

By this simple comparison of the volume of air of the aërometer, with that of the contents of the pneumatic jar, the real quantity of the gases made the subject of experiment is at once ascertained, according to the standard originally adopted; and the necessity for several calculations, and for references to the table of the changes of volume of the gases, by given changes in temperature, are at once obviated and superseded.

ART. VI. On some curious Properties of the Powers of

Numbers.

To the Editor of the Journal of Science and Arts.

SIR, A

rew years since considerable attention was excited by an American boy, who performed mentally several arithinetical operations of some difficulty, such as discovering the factors of which any number consisted, extracting the square and cube roots, &c. Having myself been present at some of his performances, I was led to consider the means by which several other arithmetical operations of, at least, equal difficulty, may be performed with facility, without the aid of writing. I have subjoined a few of the rules which occurred to me in the enquiry; and, if you deem them worthy of a place in your valuable Journal, they are much at your service.

I remain, yours, &c.

D, O. Given any number, which is a complete power of 2, to dis. cover at sight what power it is, or how many times the number 2 has been multiplied together, and produce the given nuinber.

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