strongly acid extract, which was found to consist chiefly of a peculiar tannic acid, which strikes a deep green colour with the persalts of iron. This acid, which may provisionally be termed lino-tannic acid, was also obtained in white needle-shaped crystals, by adding neutral acetate of lead to the æthereal solu tion of the plant, and decomposing the lead compound diffused in alcohol by sulphuretted hydrogen. The filtrate from the sulphuret of lead, which had an orange colour, when evaporated to dryness, afforded on treatment with æther, a solution from which, when the æther has spontaneously evaporated, crystals of the acid separated. The acid, though existing in minute quantity in the plant, has been detected both in the unsteeped and dressed flax, and possesses considerable interest in connexion with the technical preparation of the fibre, as its presence explains the discoloration which is frequently observed when the flax-straw has been steeped in water containing salts of iron. In addition to the lino-tannic acid, the straw of the flax plant was found to contain a considerable amount of malic acid, and also an acid yellow colouring substance of a resinous nature, which can be extracted by alcohol, and yields, with basic acetate of lead, a rich chrome-yellow-coloured precipitate, which, when suspended in alcohol and decomposed by sulphuretted hydrogen, and the sulphuret of lead removed, yields a straw-coloured liquid, from which, on evaporation, the resin is obtained in the form of a tenacious orange-brown extract, which is insoluble in æther, but dissolves readily in alcohol, and is precipitated from its solution in the form of a buff-coloured mass, which is dissolved by alkalies, with the production of a rich orangecoloured solution.

From the green plant, and also from the dressed fibre, water extracts a gelatinous substance which is thrown down as a bulky precipitate on the addition of alcohol. This precipitate was found to consist of pectine with malate and sulphate of lime. In the unripe plant, and also in the stems, as pulled from the field in the usual state of maturity, when the seeds contained in the capsules have commenced to assume a brown colour, starch was discovered, and could readily be extracted by placing the stems in a powerful lever press, and moistening them with a small quantity of water. By allow ing the expressed liquids to remain at rest, the starch subsides, and can be recognized by the microscope as consisting of extremely minute corpuscles, which assume a purple colour on the addition of a watery solution of iodine. When, however, the flax-straw is examined after it has remained exposed to the air for several days in the stook, the liquid obtained by subjecting it to pressure and washing with water was found to afford no indication of the presence of starch. In the dressed flax, no starch could be detected, but the presence of a considerable amount of grape-sugar was demonstrated. The discovery of grape-sugar in the fibre is in many respects exceedingly interesting, as it serves to afford an explanation of the statement frequently made by experienced steepers, that, by storing up the steeped flax as imperfectly dried, by exposure to the air for some weeks before proceeding to remove the adherent woody matters by mechanical means (by scutching), the separation of the fibre is found to be greatly facilitated, and its qualities improved.

Examination of the Steeping Process.

As stated in former communications to the Section, experiments, which were conducted by immersing flax in water, both at ordinary temperatures, and also in vats filled with water, heated and steadily maintained at from 80° to 90° Fahr., have shown that in both cases the series of decompositions which ensued might be regarded as identical, and that the fermentation 1857.

K

which takes place resembles the so-called butyric acid fermentation. Thus, when the gases which are evolved from the surface of the steeping vats are collected, which is most conveniently effected by filling the receivers with the flax water and supporting them over the surface of the liquid, the mixture of gases obtained, when transferred to the mercurial trough, and examined by the introduction of pellets of potash, explosion of the residue with oxygen, &c., according to Bunsen's excellent methods, was found, in numerous trials, to afford merely carbonic acid, hydrogen, and nitrogen. In no case could traces of carbonic oxide, carburetted hydrogen, nor of sul phuretted hydrogen be detected. The absence of sulphuretted hydrogen was carefully ascertained by the employment of various methods; not the least indication of its presence could be detected, though papers moistened with acetate of lead were exposed to the gases evolved during the entire progress of the fermentation. This fact is important, as it has been asserted that the disagreeable odour of the flax-pool depended upon the copious evolution of sulphuretted hydrogen; and its presence in the gases evolved has been reported by a French chemist, though upon insufficient evidence, afforded by the examination of flax-water, conveyed in bottles from remote parts of the country to Paris. The production of a large amount of sulphuretted hydrogen has been urged as a serious objection to the adoption of Schenck's hot-water process.

The corrected composition of 100 volumes of the mixed gases evolved from the fermenting vats was found to be as follows:

At the Belfast meeting of the Association, it was stated by the Reporter that, during the fermentation, a very considerable amount of butyric acid was produced. Since that period, the experiments have been repeated on a considerable scale, and it has been found that, though, when the fermentation has fairly commenced, after the straw has been about twenty-four hours immersed, the distillate from the fermenting liquid contains formic acid and butyric acid; yet, as the process continues, and especially towards its conclusion, the formic acid almost entirely disappears, and the butyric acid decreases in amount, and is replaced by valerianic acid. In some cases, indeed, the distillate, towards the conclusion of the period of steeping, afforded nearly pure valerianic acid.

Report of the Committee on the Magnetic Survey of Great Britain. By Major-General SABINE.

THE author gave a brief review of the important researches connected with the magnetism of the globe by MM. Kreil and Lamont, on the Continent of Europe, Dr. Bache and others in America, and by our own observers in various parts of the earth. He adverted to the Magnetic Survey of the British Islands, executed at the request of the British Association in 1837 and 1838, published in the Reports for 1838, as the first national work of this description which had been executed in any country, and to the similar works since completed in Austria and Bavaria, at the expense of the Governments of those countries, in proof of the value of the example. It is on such

surveys that we must in great measure depend for the materials on which correct delineations of the three magnetic elements on the surface of the earth can be satisfactorily based; and it is to the repetition of such surveys, from time to time, that we must look for the data on which a true theory of the secular variation of terrestrial magnetism may be founded. Twenty years having elapsed since the execution of the former Magnetic Survey of the British Islands, the General Committee had deemed that the proper time had arrived for its repetition, and named a Committee for the purpose, consisting of the same five members of their body by whom the former survey was made, with the addition of Mr. Welsh, the Director of their Establishment at Kew. The present Report stated the progress which the Committee had already made, chiefly in England and in Scotland, and their expectation that at the next meeting of the Association they should be able to report that the work was drawing near to its completion.

Report on Observations of Luminous Meteors, 1856-57. By the Rev. BADEN POWELL, M.A., F.R.S., F.R.A.S., F.G.S., Savilian Professor of Geometry in the University of Oxford.

IN submitting to the British Association my tenth Report of Observations on Luminous Meteors, I could have hoped that it might have contained some attempt at least towards the classification and generalization of the vast mass of results which have now been communicated. But while the actual contribution of fresh observations for the year which has elapsed since my last communication is not very extensive, I am also constrained to admit that I have as yet attempted very little towards the greater object in view. In the present communication, nevertheless, besides the mere detail of observations, I am able to include notices of one or two important speculations on the subject which have been pursued by some eminent men who have turned their attention to this inquiry, and have followed out some generalizations on certain points connected with it, which seem eminently valuable towards the gradual establishment of a solid theory of meteoric phænomena.

I. Some generalizations respecting the causes of meteor-phænomena, especially the averages of their horary variation in numbers through the night, have been advanced by Mr. G. C. Bompas, founded on the observations of MM. Coulvier-Gravier and Boguslawski.

The general result of those observations is, that the number of meteors varies through the successive hours from 6 P.M. to 6 A.M., by a regular increase up to the last-named hour.

The number which appear in the East is more than double the number originating in the West; those from North and South nearly equal. In other words, nearly two-thirds of the whole number originate in the Eastern hemisphere of the sky.

From the observations of Boguslawski and others, it appears that the ave rage velocity of meteors is about double that of the earth in its orbit.

Mr. Bompas, combining these facts, deduces the following theory, derived solely from the conditions of the earth's motion. The greatest number of meteors is encountered when the observer's meridian is in the direction of the earth's motion, which is at 6 A.M.; and then decreases to 6 P.M., when he looks the opposite way. If the earth were at rest, meteors (supposed equally

distributed) would converge on it equally from all quarters. But the earth, in fact, being in motion with a velocity half that of the average velocity of the meteors, it encounters nearly two-thirds of the number on the side towards which it is moving.

II. A considerable series of results has been investigated by M. A. Poey, respecting the colours of luminous meteors, derived from extensive sets of observations collected by M. Ed. Biot from those made in China from the 7th century B.C. to the 17th A.D.;-those collected in the Reports of the British Association ;-and those made at Paris by M. Coulvier-Gravier. Among these generalizations we may remark the following:

In the Chinese observations meteors of simple primitive colours are very rare, the great majority being of compound tints; in the European observations the reverse is the case.

The Chinese observations show a remarkable constancy of tints during a long period of years, when an equally constant but different scale of colour prevails; and this for several successive periods.

Cases of complementary colours in the body of the meteor and the train, or fragments, are often noticed.

Changes of colour during the course of the meteor are observed, being most usually from white near the zenith to blue near the horizon, but sometimes from white to red. This, the author observes, agrees with the law of M. Doppler, that a luminous body moving towards the observer will change its colour from white, in succession to the violet end of the spectrum ;moving from the observer, to the red. This law, he states, is especially confirmed by the Paris observations. He remarks on the necessity for attending to personal differences in observers' estimate of colour; a remark fully confirmed by the great contradictions existing in the descriptions of the colour of many of the brightest meteors, at the same time and place, by different observers.

He gives the results of the various observations cited, in tables exhibiting the number of meteors of each tint for each month; and adds others of meteors arranged under several heads, of physical peculiarities.

The details are given in the Appendix No. 4.

III. One point of the highest interest and importance towards forming any sound theory of meteors, is the estimate of their actual size from their apparent diameters and calculated distance. In all the results usually given this calculation is made on acknowledged geometrical principles, assuming that the apparent disk is the real one, diminished only by the effect of distance.

Prof. J. Lawrence Smith of the U. S. has adduced some very remarkable optical experiments to show the entire fallacy of any conclusion from the apparent diameter of a highly luminous or incandescent body seen at a distance.

These experiments exhibit a singular apparent enlargement of the visible disks of intensely luminous bodies of known size, when observed successively at distances of 100 yards, of a mile, and mile; at which distances respectively, for example, the body of electric light of carbon points (actually 03 inch diameter) appeared, 3 times, and 3 times the diameter of the moon; and other incandescent bodies in a similar proportion dependent on the degree of ignition.

These results seem dependent on some optical or ocular cause, of greater energy than we can ascribe readily to simple irradication; but in a rough way they admit of some degree of verification by looking at a row of street lamps seen nearly in a line from the eye, the apparent diameters of which do not

decrease at all for a considerable distance; and even then by no means in proportion to the law of perspective.

This subject appears to be one eminently deserving of more full and precise investigation, whether in a meteorological or an optical point of

view.

IV. Prof. Lawrence Smith's paper is, however, mainly devoted to other points of not less importance respecting the nature and theory of meteors, and especially of those which fall either wholly or in portions, producing meteoric

stones.

He gives a minute account of five specimens found in America, accompanied by chemical analyses, from which it appears that they all contain the mineral called Schreibersite, not known as a natural compound on the earth. He enters largely on theoretical views, and in the course of these speculations examines various hypotheses which have been put forth, and eventually endeavours to revive the theory of the origin of these bodies from the lunar volcanoes supposed at some remote period to have been in a state of activity. Without discussing such a question, which will perhaps be generally viewed with suspicion at the present day, and passing to the general subject of shooting stars, which the author is inclined to distinguish entirely from those masses which have fallen to the earth, we may notice the apparently favourable mention he makes of the general admission of the cosmical nature of the former, and of that view of their nature which regards them as nebulous masses revolving in our system.

It has been further supposed that such masses, being in a high state of electric tension, on approaching the earth, a discharge might take place by which their metallic elements might be reduced: dependent on the size of the nebulous mass, the force of the discharge, the consequent intensity of the fusion, and other conditions, larger or smaller metallic or earthy masses might be precipitated, and might fall entire or shattered into fragments. The author, however, considers these latter effects as incompatible with the conditions of observed meteorites.

But probably, on the whole, all such speculations are as yet premature. We must obtain a larger amount of data and better classification of observations before we can hope to follow out such inferences successfully.

For the details of Prof. L. Smith's paper see Appendix No. 5.

V. In some of the earlier of this series of Reports, reference was made to the theory proposed by Sir J. Lubbock, of meteors shining by reflected light and being simply darkened by entering the earth's shadow, and to some observations of meteors which coincided with it. It is much to be regretted that other observations of a kind capable of such application have not been more frequent. One remarkable instance observed by Capt. Jacob, at Bombay, was considered some years ago by Prof. C. P. Smyth, and a communication on the subject made by him to the Royal Society of Edinburgh (1849), of which a short notice in the Proceedings of that body is the only remaining record—the details having unfortunately not been preserved. The results, however, are stated to accord exactly with the theory.

The essential parts of the notice are given in Appendix No. 6.

VI. Of the August meteors for the present year, the only notice which has reached me has been an account published by Dr. T. Forster, of Brussels, in the Times. He observed great numbers, some of them presenting unusual appearances, especially in regard to colour.

His letter is given in Appendix No. 7.