By the means of this system, combined with the Mechanical Notations, it is now possible to express the forms and actions of the most complicated machines in language which is at oncce condensed, precise, and universal.

At length, in November 1842, Mr. Babbage received a letter from the Chancellor of the Exchequer, stating that Sir Robert Peel and himself had jointly and reluctantly come to the conclusion that it was the duty of the Government, on the ground of expense, to abandon the further construction of the Difference Engine. The same letter contained a proposal to Mr. Babbage, on the part of Government, that he should accept the whole of the drawings, together with the part of the engine already completed, as well as the materials in a state of preparation. This proposition he declined.

The object of the Analytical Engine (the drawings and the experiments for which have been wholly carried on at Mr. Babbage's expense, by his own draftsmen, workmen, and assistants) is to convert into numbers all the formulæ of analysis, and to work out the algebraical development of all formulæ whose laws are known.

The present state of the Analytical Engine is as follows :

All the great principles on which the discovery rests have been explained, and drawings of mechanical structures have been made, by which each may be carried into operation.

Simpler mechanisms, as well as more extensive principles than were required for the Difference Engine, have been discovered for all the elementary portions of the Analytical Engine; and numerous drawings of these successive simplifications exist.

The mode of combining the various sections of which the Engine is formed has been examined with unceasing anxiety, for the purpose of reducing the whole combination to the greatest possible simplicity. Drawings of almost all the plans thus discussed have been made, and the latest of the drawings (bearing the number 28) shows how many have been superseded, and also, from its extreme comparative simplicity, that little further advance can be expected in that direction.

Mechanical Notations have been made both of the actions of detached parts and of the general action of the whole, which cover about four or five hundred large folio sheets of paper.

The original rough sketches are contained in about five volumes. There are upwards of one hundred large drawings.

No part of the construction of the Analytical Engine has yet been commenced. A long series of experiments have, however, been made upon the art of shaping metals; and the tools to be employed for that purpose have been discussed, and many drawings of them prepared. The great object of these inquiries and experiments is, on the one hand, by simplifying as much as possible the construction; and on the other, by contriving new and cheaper means of execution, at length to reduce the expense within those limits which a private individual may command.-Taylor's Scientific Memoirs, vol. iii. part 12.

SIMULTANEOUS MAGNETICAL AND METEOROLOGICAL OBSERVATIONS.

THE following is Sir J. W. F. Herschel's Report of the Committee appointed to conduct the co-operation of the British Association in the system of simultaneous Magnetical and Meteorological Observations. The report commences with referring to the proceedings of the Antarctic Expedition. Three seasons, in which the ships have forced their way at different points far within the higher latitudes of the southern hemisphere, have furnished a magnetic survey of these regions, equalling, or rather surpassing, both in completeness and accuracy, all those sanguine expectations which led the Association to urge on the government the prosecution of this great enterprise. The magnetic observations of the Expedition which had been sent bome, were in course of publication by the Royal Society. In the last of these contributions to terrestrial magnetism, the important subject of the corrections due to the iron of the ships is fully considered, and by the aid of formulæ, furnished by Mr. Archibald Smith, of Trinity College, Cambridge, and founded on the theory of M. Poisson, delivered in his Memoir of 1838, "Sur les déviations de la Boussole produites par le fer des vaisseaux," the constant co-efficients of their corrections for each ship are investigated. The corrections deduced from these elements are found to agree admirably with the results of experiment, thus affording ground for the fullest confidence in the corrections depending on them, as well as in the theory from which they are derived, and in the general approximation to truth of the hypotheses necessarily made as to the distribution of the iron in the vessels. All the results being tabulated and projected in charts, the inspection of these gives room for the following interesting remarks:1st. As great discordances are to be looked for, and must frequently be experienced in magnetic surveys conducted on land, as in those at sea, and even greater. In effect, the chief and worst cases of accordance occur in observations made on islands. 2d. The general form of the curves of higher inclination in the southern hemisphere is much more analogous to that in the northern, than appears in M. Gauss's maps. 3d. Capt. Ross's observations of intensity lead also to the conclusion of a much closer analogy between the two hemispheres than M. Gauss's maps would appear to indicate. No higher intensity than 2.1 has been anywhere observed. 4th. In examining the observations of declination, particularly those which point out the course of the lines of 0° and 10o east, a more westerly position is indicated than that assigned by M. Gauss for the spot in which all the lines of declination unite. The Report then mentioned that the government of the United States has assigned funds for a magnetic observatory at Washington, as well as for a further three years' continuance of that already established at Philadelphia. The Bavarian government also has consented, on the application of the Royal Society, to maintain for an additional three years the observatory at Munich. The first part of the volume of Disturbance Observations has been completed, comprising those made in 1840-41. Col. Sabine has prefaced this

volume with a synoptic statement of the general conclusions, which it has been found practicable to deduce from the observations in their actual uncorrected state, of which conclusions thefollowing is a brief outline :-At Toronto the march of the regular diurnal movements in declination does not consist in a simple uninterrupted progress and regress of the needle. Commencing from 2 P.M., its movement is continuous to the eastward till 10 P.M.; it then returns westward (through a comparatively small angle) until 2 A.M., when its eastward movement is resumed and continued till 8 A.M., after which its return is continuous to the west until 2 P.M. This second eastward progression is more decided in summer than in winter, and in the total range of diurnal fluctuations is also more considerable. At Van Diemen's Land (a station, it is to be borne in mind, almost antipodal to Toronto), the course of diurnal oscillation agrees with that above stated in all but one feature-viz. that the hours (in mean time at the station) of easterly movement of the north end of the bar at the one station are those of its westerly movements at the other; that the diurnal range is nearly the same in both, with a similar inequality in its summer and winter amount; a similar alternate progression and recess also prevails, and at the same hours. These are certainly very remarkable features, showing a regular connexion between two stations so remote, carried out into what may be regarded as minute particulars, Falling in, however, with the generally received impression of the universality of the causes (whatever they may be) which produce the periodical fluctuations of the magnetic elements, they can only be regarded as contributions to our knowledge of details. It is otherwise with the results deduced, by a comparison of the observations recorded in this volume, not only at these two stations, but also at St. Helena, with each other, and with those made by M. Kreil at Prague, as respects cases of unusual magnetic disturbance which occur (as far as we can yet perceive) casually, or at least not periodically. Such comparison has enabled us, at length, unequivocally to state it as a general proposition, that the whole magnetic system of our globe is affected, in the majority of cases of great disturbance; for it is found that if a list of days of great disturbance, independently noticed as such, and marked by extra observations on each station, be made out, these lists will be found to coincide in at least a majority of days, and more especially in those days when the recorded disturbance has been greatest. Of twenty-nine principal disturbances recorded in Col. Sabine's synoptic table, some confined to a single day, others running through two or three successive days, and comprehending altogether forty-nine days, by far the greater part are shown to have manifested themselves at Toronto, Van Diemen's Land, and Prague, and fifteen are marked by extra observations at St. Helena. But though it is thus rendered certain that the whole globe is affected in many and great magnetic storms, it is equally shown that the minute identity of particular shocks, which seemed to result from the earlier observations of this nature in Europe, is not in general traceable on any thing like so ex

tensive a scale. Not the least interesting part of this volume consists in the notices at Toronto of auroral phenomena accompanying the extraordinary magnetic disturbance; they are many and remarkable, and can hardly fail to throw great light on this branch of the present subject. The difficult subject of the determination of the earth's magnetic force in absolute measure has been subjected to a further investigation by Dr. Lloyd. The difficulty which it presents is of a practical rather than a theoretical nature, and arises from this, that the expression for the tangent of the angle of deflection of one magnet by another involves co-efficients, which have to be determined in Gauss's method by observations of deflection at two different distances and by elimination, in which process serious errors are introduced in the result by small errors in the observations. The object of Dr. Lloyd has been to point out a method by which the quantity sought may be obtained without elimination by observations at one distance only, thus both diminishing the trouble of the observation, and increasing the accuracy of the result. This method depends on the assumption of an empirical law in the distribution of free magnetism in a magnetical bar, inferred by Biot from Coulomb's researches. Dr. Lloyd adduces several experiments confirmatory of these results. The Report next mentioned Lieut. Lefroy's intended course for magnetic survey in North America as far north as the Great Slave Lake. He crossed the line of no variation between La Cloche and Sault St. Marie, up to which point little change of dip had been experienced, his course leading nearly along the isoclinal line of 77°. The second series of Sir E. Belcher's observations, determining the magnetic elements of 32 stations (the two series embrace 61 stations) in the Pacific Ocean, the Indian and Chinese Seas, are now printed in the Philosophical Transactions.

174

Electrical Science.

ELECTRICITY OF STEAM.

ON June 9, at the Royal Institution, Prof. Faraday illustrated the extent of our knowledge of the Electricity which accompanies the formation of Steam, previous to showing that when water is poured into a heated metal cup electricity was set free; and that if the vessel, into which the water was placed, was above a certain elevated temperature, no electricity was evolved, in consequence of the water being prevented from contact with the containing vessel by a stratum of steam. The Professor then detailed the first observations made at Newcastle by one of the workmen in attendance on a boiler belonging to the Newcastle and Carlisle Railway, and whose report, that the boiler was full of fire, from the fact that when he placed his hand near it an electric spark was communicated, drew the attention of Mr. Armstrong to the subject, the result of whose investigations was then given.* A boiler having been arranged for the purpose of illustrating this subject, the Professor exhibited the production of the spark during the emission of the steam, and showed most conclusively that the boiler and appendages were charged with negative electricity, while the issuing steam was in the opposite or positive state; that it was necessary that the boiler should be insulated; that the steam should issue through a small aperture; that the material of which this aperture was constructed modified materially the quantity of electricity, wood and the metals having been found by experiment to be the best fitted for the purpose; that the introduction of a small portion of saline matter, as sulphate of soda, into the exit chamber, prevented entirely the elimination of electricity, and even when common water was introduced it had the same effect; that by long continuance of the issuing current of steam, electricity was gradually developed, from the condensed steam displacing and driving out the saline matter, pure water being a necessary element for its production; and that the whole phenomena arose from the rubbing of the condensed water against the tube from which the steam was issuing. The Professor also proved that the introduction of ammonia reversed the electrical states, what was before negative becoming positive, and that as the ammonia was expelled the original states were gradually restored; that turpentine and acids acted in the same way as saline substances, from their enveloping the particles of water in a film of their own substance. The lecturer considered, from these facts, that the view advocated by Mr. Armstrong, that the electricity arose from the passage of water into the aeriform state, was not tenable, and that the thunder-cloud and the lightning's flash could not be attributed to this origin.

See Year-Book of Facts, 1841, p. 132; Year-Book, 1842, p. 133; YearBook, 1843, p. 169.