indeed, as to be scarce worth taking into account; and that the enlarging the diameters of the wheels is also of very questionable utility. There is but one thing which Government, as at present constituted, can do for scientific men, and that is the one thing which is not thought of. It is absurd in the State to confer upon them what it calls honours; but it may afford them the means of subsistence, not as a reward, but to enable them to devote themselves to their scientific pursuits, without hindrance from those petty occupations which they are mostly obliged to follow for their daily bread. Every person of scientific eminence, whose genius and acquirements, destined at the best to perish soon ont of the world, are in a great measure lost to it while he is living, for want of some small provision which would keep him independent of mechanical drudgery-every person of distinguished intellectual powers, whom society has not sense enough to place in the situation in which he can be of the greatest use to it-is a reproach to society and to the age in which he lives. It is here, if any where, that improvement may be hoped for; and we hope it is here that we shall in time see it contended for.-Monthly Repository. Some well divided scales, by Troughton, were lately compared with others by Elliott-both of them instrument-makers of the very highest reputation-when there appeared to be a difference between them of .34 of an inch in a foot. Now, in laying down a plan of 5 chains to an inch, this would make a dif ference of about 17 links in every 12 inches in length; which, in a survey of any considerable extent say 1,000 acres-might cause a loss or gain of some hundreds of pounds. Such discrepancies as this might be avoided by instrument-makers agreeing to adhere to one certain standard; and, in an age of science like this, it seems wonderful that this has not been yet done.-Wm. AndrewsIvinghoe, Bucks, June 2, 1834. We are informed by the same intelligent correspondent, to whom we are indebted for the preceding note, that he has found by experiment, that India rubber will not properly dissolve in sulphuric ether (as stated in our Journal of the 26th of April last, on the authority of Dr. Mitchell, of Philadelphia), but yields completely to spirits of turpentine. The properties of the Portland stone, the trade in which promises to be so greatly facilitated by the formation of the Portland Breakwater, are thus noticed in the Guernsey Star:-" The freestone, one continued bed of which runs nearly through the whole island, is well-known for its solidity, durability, and beauty. It was brought into repute in the time of James the First, and was em ployed in the construction of the Banquetinghouse at Whitehall, in 1610. After the fire of London, vast quantities of it were conveyed there, and used by Sir Christopher Wren in the building of St. Paul's, and different public edifices. The piers and part of Westminster new bridge, and the whole of Blackfriars-bridge are built of Portland stone. Dr. Maton observes, that the name of freestone is very expressive of the useful property of the Portland stone, in enduring to be cut in any direction, whether horizontal, perpendicular, or parallel to the site of the strata, while it bears the injuries of the weather equally well in every position.' The rocks form a barrier round the island, except at the landing-place on the north, where Portland castle is situated." On the 26th of May, Orleans and its environs were, during the whole morning, covered with a dry and fetid fog, driven by a cold and violent breeze from the north-east, and resembling in appearance and odour the smoke of burning lime. The light of the sun appeared as during a partial eclipse. These phenomena seem to justify the hypothesis of Arago, in the Annuaire of 1832, as to the cause of such fogs, in which he supposes that they may originate from the vapours of an immense furnace in the centre of the earth, which have escaped through fissures in its crust, or from some distant volcano, the smoke of which has been wafted by the wind in one particular direction, or from some body foreign to our globe, which has burst by its own internal fire, or been disruptured by the shock of some comet.-French Paper. A letter, of the 3d inst., from Rodelheim, near Frankfort, quoted in the French papers, says,"During some heavy showers of rain which fell yesterday, from half-past eleven to twelve o'clock, and to-day from twelve to one, the water contained so great a mixture of sulphur, that, as it ran down the streets, it was covered with a yellow crust, and quantities of sulphur might be scraped from off the pavement." German Silver.-The solder generally employed consists, we believe, of an alloy of the German silver itself with tin. For cleaning, S.D. should employ wood ashes, or ivory black well washed and sifted. In the Committee on the Bristol Railway, Mr. James Walker, C.E., said," We are making an experiment (I believe it is new) upon the Leeds and Selby Railway, with the intention of lighting the tunnel by shafts from the surface, and placing at the bottom of these shafts, and nearly at the top of the tunnel, reflectors. The rays of light falling perpendicularly upon the reflecting medium suspended at a considerable angle, are reflected into the tunnel. As far as the experiment has gone it has been very successful. The ends of the tunnel have been darkened, and a newspaper read in the tunnel by the reflected light." So intense has been the heat of the sun's rays during the past month, that between two and three P. M., on the 31st, a thermometer, whose bulb was covered with black wool, rose to 130°, with a gentle wind from the south-east, and cirrus prevailing in the vicinity of the sun at the time. The mean temperature of the external air for May has been nearly two degrees higher than the mean of May for a series of years.-Dr. Burney's Meteorological Report-Hampshire Chronicle. A gentleman in this town (Kirkaldy) has lately received a letter from his son, who is first mate of a vessel now in the Mediterranean, in which he says, "The vessel is built on Ballingatt's plan, and the consequence is, we have never had occasion to touch the pumps since she left England, about two months ago"-Edinburgh Observer. Canine Shower-bath.-A dog may be seen, most mornings, in the neighbourhood of Brunswicksquare, enjoying the luxury of a bath at the tail of a water-cart. He watches for the arrival of the cart, and then follows it a considerable distance, bounding and frisking in the jets. It is quite a refreshing affair to the actor, and to the spectators also. Communications received from Mr. De Blaquiere -R S-Momus-Mr. Blackett-Mr. HalliganR. (Halifax.) The Supplement to Vol. XX., with a Portrait of William Symington, is now ready, príce 6d. also Vol. XX., complete, in boards, price Ss. LONDON: Published by M. SALMON, at the Mechanics' Magazine Office, No. 6, Peterborough Court, between 135 and 136, Fleet-street. Agent for the American Edition, Mr. O. RICH, 12, Red Lion square. Sold by G. G. BENNIS, 55, Rue Neuve, Saint Augustin, Paris. M. SALMON, Printer, Fleet-street. Mechanics' Magazine, MUSEUM, REGISTER, JOURNAL, AND GAZETTE. MAP OF MAGNETIC CO-VARIATION LINES IN AMERICA AND THE ATLANTIC, AND ALSO PARTS OF EUROPE, ASIA, AND THE PACIFIC, Stereographically transferred from the Circum-Polar and Equatorial-Maps of Professor Barlow. 194 MAP OF MAGNETIC CO-VARIATION LINES. [We have been induced to present our readers with the substance of this interesting paper, on account of the very limited circulation which the original Transactions receive, especially those Parts which are charged at a high price. The magnetic lines are, in the original, traced on a circumpolar map of 30° radius, and an equatorial one (Mercator's) extending from 60° N. to 55° S. The author regrets the want of continuity in the curves occasioned by this method, and remarks that they ap pear to much greater advantage when traced on a real globe. We have translated the most interesting portion of his maps into the form suggested by a correspondent of the Mechanics' Magazine (xx. 168), a change which, we imagine, the author will approve, should these pages fall under his notice.] The author has undertaken the task of collating and arranging all the valuable information recorded in several recent and important voyages and journeys of discovery, conducted by officers of high scientific character, and furnished with instruments of the most perfect description. He particularly mentions the voyages of Captains Beechey and Biscoe, the surveys of Captains Owen and King, the voyages of Lutke (Russ.) and Duperney (Fr.), the materials in the hydrographical offices of Captains Beaufort and Horsburgh; and lastly, the numerous experiments of Commander Ross in the immediate vicinity of the magnetic pole. These, together, formed such a mass of well-authenticated observations, as seemed to render it very desirable to put them into a form for future comparison, if not for immediate investigation. The author has only laid down such lines as were warranted by actual observation; the deficiencies exist chiefly about the South Pole, and over lands, except in Europe. On attentively examining these lines, especially on a globe, the author thinks that, notwithstanding their extraordinary curvatures, they exhibit a dependency on some law, however intricate and mysterious. If the variations were greatly influenced by local causes, we could not expect to find that regularity. which is observable in so many, if not in all parts. Throughout the Atlantic, for In many parts each degree of variation is exhibited by a distinct curve, in others, the multiples of 5 or 10% only. 4 example, there is a continuity and softness of curvature, and unity of character, quite inconsistent with such a supposition. Again, in the Indian Ocean, we have a most extraordinary inflexion of the line of no variation, whereby twothirds of the equator, or 240o, have easterly variation, and only 120o have it westerly. In both cases, the multitude of observations which have been discussed leave no doubt of the correctness of the delineation; and we see no such sudden interruption of curvature as must occur if local causes were very influential. Another marked peculiarity in the Indian Ocean is, that for 40° the zero line runs nearly parallel to the equator, and therefore 400 down a meridian, whence it follows that the magnetic pole must also range through 40°, or be coincident with the axis; either of which conditions is equally inconsistent with the notion that all these phenomena are due to the action of four or more magnetic poles. Again, referring to the remarkable curves in the great Pacific, there is, notwithstanding their peculiar character, no appearance of uncertain or anomalous attraction; the whole seems to form a system by itself. The lines return upon themselves in similar though not in regular figures: and here again the author can see no possible position of four poles which can lead to such configuration. The foregoing remarks have reference to the present state of the magnetic lines; but their progressive change of situation The Asiatic line of no variation presents a range of curvature strongly contrasted with the American. In the lat. of 80° N., its longitude is about 37° E. (just at the border of our map). After passing southerly for some degrees, it takes a sweep like the letter S through Asiatic Russia (see Hansteen's Chart, Edin. Phil, Journ., 1821), and comes out at the Sea of Ochotsk; then passing southward through the Sea of Japan it bends westward, touching the N. point of the Isle of Formosa. It must then take another sweep through China and Thibet, for it enters the Indian Sea at the Gulf of Cambay, and crosses the equator in 75° W. lon., and (according to Barlow), after following for 20o the parallel of 10° S., it reaches Vansittart Bay, on the N. coast of Australia. On the S. coast it is found in long. 130 E., and follows that meridian to an indefinite extent. Hansteen's Chart gives it a most incredible sinuosity through the Chinese Seas and among the Indian Islands. In the Pacific Ocean the variation is wholly eastern, the minimum point being 135° W. long. and 19° S. lat., and its value there less than 5, and the curves of the several values up to 100 va riation, form continuous heart-shaped curves round this centre. MR. RUTTER, ON FLAME AND COMBUSTION. and configuration is another important feature. From some early notices, the author infers that, about the year 1660, the line of no variation must have crossed the Atlantic nearly at right angles to the meridian, as it does now in the Indian Ocean. From that time it has been gradually descending towards the south and west; and at present crosses some way inland on the eastern point of South Amèrica. We have no such early authority for that zero line which passes through Australia; but it seems probable that for the last sixty years very little, if any, change has taken place. In all known cases, except these two, the motion for some years before and after the passage of the zero line over any spot has been very rapid, whereas in these it is nearly stationary. Thus, in London, the variation in 1580 was 110 15' E.; in 1658, zero; in 1698, 8o W., giving a change of 20° in little inore than 100 years; and the same is observed in all other places, except the two referred to, where the passage of the line is well determined. In the West Indies, the Bermudas, and a few other places, where the variation is small, the change has also been very inconsiderable; but the author has found no case where the variation is large and stationary. Churchman first assumed, and the author finds the theory confirmed in all cases where sufficient registers of variation have been made, and where the motion or change has been considerable, that we may always reduce that motion to a certain rotation of an assumed magnetic pole about the pole of the earth. The author has compared the actual and computed variation for different periods, at London, Paris, and Copenhagen, and finds the agreement between them very considerable, and he infers that the hypothesis of a polar revolution must be founded in fact. He also accounts for those stationary, or nearly stationary, points of no variation to which reference has been made, by supposing that there is no determinate pole to which all needles point, but that every place has its own particular pole and polar revolution, governed, probably, by some one general but at present unknown cause. If, then, * Encycl. Metrop. Art. Magnetism. 195 the magnetic pole of any place should be nearly coincident with the terrestrial pole, the line of no variation, notwithstanding the rotation, must remain nearly stationary; but where the variation is considerable, the change would be very slow while it is passing through its maximum. J. W. W. ON FLAME AND COMBUSTION-MR. RUTTER Dear Sir,-An apology is due from me to yourself, and to Mr. Witty, for noticing, so long after date, some remarks in that gentleman's paper, Mech. Mag., No. 545, vol. xx. p. 269. I consider some of Mr. Witty's observations are not consistent with analogy and direct experiment. As may be expected, I am chiefly concerned with those which have a distinet reference to myself. * Having very recently brought together a somewhat formidable list of experiments as illustrative of the phenomena of flame, and having also, on the same occasion, expressed my views as to its theory, it seems unnecessary to enter very minutely into Mr. Witty's observations on that subject. Mr. Witty's theory is very ingenious; but, I think, it is wholly unsupported by experiment. To me it is inexplicable how aqueous vapour can be "projected into the interior of the flame" of a candle, at the same time that a current of gaseous and vaporous materials is flowing in an opposite direction. Neither can I understand how the liberated and combining elements "play backward and forward many hundred times in a second." That idea is too refined and too complex for my imagination. Moreover, the theory of combustion, as exhibited in a candle, is perfectly intelligible, without having recourse to any such rapid and mysterious movements as are hinted at by Mr. Witty. With that part of Mr. Witty's paper, in which there is an allusion to my heating process, I am more immediately concerned on the present occasion. I proceed, therefore, to its examination. To the inquiry, "Is it possible, then, to burn coal-tar without producing smoke?" (p. 271.) Mr. Witty replies, "Nothing is more easy to a person pos * Mech. Mag. No. 564, pp. 140-147. 196 MR. RUTTER, ON FLAME AND COMBUSTION. sessing a slight knowledge of chemistry. Let a long tunnel of fire-brick be constructed leading to a chimney, and let a coal-fire be lighted till the sides of this tunnel become of a white heat. If a small stream of coal-tar be now introduced it will inflame, and as the particles of carbon deposited (disengaged?) cannot lose their heat, and will be floating in a strata of air heated to redness, (?) their union with oxygen must take place, provided sufficient air be admitted with the stream of coal-tar." Mr. Witty has not told us whether it will be necessary to keep up the coal-fire after the sides of the tunnel become of a white heat, and the stream of coal-tar has been introduced. This is very important in determining about the cost of the process, as compared with others for generating heat. Perhaps we may be able, by-andby, to understand this matter more satisfactorily. That the chemical union of hydrogen, carbon, and oxygen, in the process of combustion, is attended by the extrication of heat, and that the quantity (or) intensity) of heat evolved in the combustion of a given quantity of fuel, depends very much on the quality of that fuel, and the treatment to which it may be subjected, are facts with which every chemist is, or ought to be, familiarly acquainted. Those kinds of fuel in which the elements of inflammability are assimilated in the most suitable proportions, for entering readily into combination with oxygen, yield, from a given weight of the inflammable body, a greater quantity (or intensity) of heat than can be obtained from the same weight of fuel, wherein one of the inflammable elements may be excessive, whilst another may be deficient. We find this indicated in the following experiments of Dr. Dalton, which are not, perhaps, rigidly exact; but they are, undoubtedly, highly important as proximations : ap 8 Carburetted hydrogen 6 Olefiant gas Carbonic oxide It demands our attention that, next to hydrogen and oxygen, in a gaseous form, the greatest quantity of heat is obtained from olive oil, wax, and tallow, in combination with oxygen; and whilst 1 lb. of hydrogen requires 8 lbs. of oxygen for its complete combustion, 1 lb. of olive oil requires only 3.033 lbs. of oxygen. We may hence conclude that about 3 lbs. of olive oil, and rather more than 9 lbs. of oxygen, will yield the same quantity of heat as the direct union of 1 lb. of hydrogen and 8 lbs. of oxygen, in their gaseous state. It is further deserving of remark, that those bodies in which an excess of carbon resides, as oil of turpentine, char-` 3.5 coal, and caoutchouc, give out, in combustion, a much less quantity of heat than some other bodies in which hydrogen and carbon are assimilated in more exact proportions. For example:-1 lb. of olive oil and 3.033 lbs. oxygen produce sufficient heat to melt 104 lbs. of ice, whilst 1 lb. of oil of turpentine and 3.14 lbs. of oxygen will melt only 60 lbs. of ice. It is but fair to conclude that, at least, one third part of the oil of turpentine escaped as lamp-black in an uncombined state. Suppose that, by some specific arrangement, the whole of the 1 lb. of turpentine could be made to combine with oxygen, instead of 3.14 lbs. of the latter element, there would be re |