or the rope, and such lines might also generally be constructed at less cost by the adoption of this mode of working, so as to pay for the additional expenditure.

The circumstance of a railway being throughout on one inclined plane, so that the carriages will run down with their own gravity, as on the Dalkey line, is favourable to the atmospheric system.

The locomotive system would, however, also derive advantage from the same cause, as the engine would return without using any steam.

2ndly. That on any main line, with the average number of trains, the interest on the cost of the atmospheric apparatus amounts to the present actual annual cost of working by locomotive, and consequently, it cannot be applied to any line or branch worked as part of the same locomotive establishment, without an actual annual loss, amounting to nearly the whole cost of working the atmospheric engines.

It must also be evident, that it can never be applied to new lines, under ordinary circumstances without actual loss, as no reduction in the cost of the pipe can be made by the alteration of the gradients. If the mode of rendering the pipe air-tight could be improved, so as to work lengths of 10 or 15 miles each with one engine, it would much reduce the loss of power; but these lengths would cause several practical inconveniences if they could be obtained.

3rdly. That a great cause of lost power arises from all modes of working a railway by stationary engines, inasmuch as the steam must be kept up the whole 24 hours; while the locomotive power is practically required for a few hours only. This will amount, assuming the average number of trains on railways, to three or four times the consumption of fuel by the stationary principle. It may be said, that when applied to long lines, a greater number of small trains would be run, instead of a few large ones; and this would certainly be the best plan. How far the increased traffic, arising from these facilities, might pay the additional cost, it is impossible to say; but with any number that can be run with advantage, the locomotive would be the least expensive method, unless under peculiar circumstances. There is also another objection arising from the amount of work which is required to be done at stations by locomotives, and also the intermediate work of various kinds, this, with the atmospheric system, must be done by horse or manual labour at a much increased cost.

There is also the risk of certain stoppages of the traffic with the atmospheric railway, not only from the stationary engines getting out of order, but from the frequency

(with every care that can be employed) of obstacles on the road, which will throw a carriage off the rails; injury to the pipe, by slips and subsidences, &c. These are of frequent occurrence in embankments, and in a common road they can be repaired in a few hours, but they would be sufficiently extensive to entirely destroy the action of the pipe, and would stop the traffic for a conderable period.

4thly. The most favourable feature in the atmospheric plan is the advoiding the noise, both of the locomotive and the rope, and this will lead to its adoption on short lines in the neighbourhood of towns, as it will be the less objectionable to the residents in the neighbourhood; and in these case, as the trains are required to be numerous, and locomotive power on the small scale becomes comparatively costly, the advantages of economy will also be in its favour; in other words, in such cases, where stationary power has or may have been previously used with economy, the atmospheric mode of traction would be advantageous; but whatever improvements may be made in its construction, it must still possess the essential features of the stationary principle, and must therefore, as has been previously shown, not admit of application to a railway of general traffic.

The attainment of lengths of 10 miles each would evidently reduce the great cause of loss of power in the present atmospheric railway; but it would increase the inconvenience which must arise on long lines, from the absolute necessity of intermediate power, and where two trains meet, it is evident they must both wait, during the time the air is exhausted out of 10 miles of pipe, which will not be less than 20 minutes or half an hour, unless stationary engines of very large power be used.

The result, as to the effect of the resistance of the air at high velocities, is very interesting. It has been shown by experiments, that when a train attains a velocity of 35 miles per hour, the resistance from this cause equals 50 per cent. of the tractive force, and that it increases rapidly with higher velocities; this is fully proved by the effect of windy weather on passenger trains; but it is remarkably illustrated by a circumstance which occurred on the Canterbury and Whitstable railway, since it has been under the author's charge (and it appears to have been of frequent occurrence). A train was entirely stopped in descending a gradient of 1 in 50, rendering it necessary to use horse power, although the velocity of the wind at the time could not have exceeded 60 or 70 miles per hour.

The result arrived at, that the average

be realized.

With reference to the lines on which the atmospheric system is in course of execution, viz., the London and Croydon, and South Devon, the results arrived at in the above investigation show, that the London and Croydon (if not forming a portion of a trunk line), is a case in which the power can be comparatively applied with advantage, and the objections only apply to a limited extent, as the trains are frequent, and the traffic consists chiefly of passengers, and as there need be only one train met, the speed with a single line will probably be greater than with the locomotive engine, from the time necessary with frequent stoppages, to get the locomotive engine up to its speed.

The New Cross incline will be felt to be the greatest objection, as the speed will be small (with the power proposed), with large trains, from the increased tractive force which will be necessary.

The South Devon line is a case, to which it would appear from the above results, that the atmospheric system is not adapted.

[The discussion which followed the reading of this Paper we shall give in a subsequent number. ED. M. M.]

CASE IN RAILWAY ENGINEERING.

There are three towns, A, B, C, communicating by railway, all situated on the same level plane, but not in the same straight line with each other: between these towns the mutual distances are as under, viz.: 25 miles 31 29 22

From A to B....

From A to C.

From B to C.... At 12 miles distance from A in a straight line is a station of supply, at which the branches to B and C diverge. Now, since it was optional with the engineer to place that part of the trunk line between A and D in any position he pleased-what would have been its position with respect to the branches DB and D C, and what would have been the lengths of these branches, had they been laid down in such a manner, as to form jointly the least length possible?

111

PROFESSOR PAGE'S MAGNETO-ELECTRIC

MACHINE.

In 1838, Professor Page published in Silliman's Journal an account of an improved form of Saxton's magneto-electric machine, doing away with many existing objections, and furthermore rendering it at once a useful instrument, by a contrivance for conducting these opposing currents into one channel or direction, which part of the contrivance was called the unitress. The current produced in this way was capable of performing the work, to a certain extent, of the power developed by the galvanic battery; and the machine was found adequate to furnishing of shocks for medical purposes, for exhibiting the decomposition of water, furnishing the elements of oxygen and hydrogen at their respective poles, and producing definite electro-chemical results. These two last results could not be obtained without the aid of the unitress. But, with this improvement, the instrument was still wanting in one property of the galvanic batteryviz., that property which chemists call quantity, or that power upon which depends its ability to magnetize, and also to heat platinum wires. This last property has been given to the machine by the recent contrivance of Professor Page. The machine, in its novel construction under his improvement, developed what is called by way of distinction, the current of intensity, but had a very feeble magnetizing power. By a peculiar contrivance of the coils, (not to be made public until his rights are in some way secured,) the current of quantity is obtained in its maximum, while at the same time, the intensity is so much diminished that it gives scarcely any shock, and decomposes feebly. It has been successfully tried with the magnetic telegraph of Professor Morse, and operates equally well with the battery. It affords, by simply turning a crank attached to the machine, a constant current of galvanic electricity; and as there is no consumption of material necessary to obtain this power, it will doubtless supersede the use of the galvanic battery, which, in the event of constant employment, would be very expensive, from the waste of zink, platinum, acids, mercury, and other materials used in its construction. It particularly recommends itself for magnetising purposes, as it requires no knowledge of chemistry to insure the result, being merely mechanical in its action, and is always ready for action without previous preparation; the turning of a crank being the only requisite, when the machine is in order. It is not liable to get out of order; does not diminish perceptibly in power when in constant use, and actually gains power when standing

at rest. It will be particularly gratifying to the man of science, as it enables him to have always at hand a constant power for the investigation of its properties, without any labour of preparation. We notice among the beautiful results of this machine, that it charges an electro-magnet so as to sustain a weight of one thousand pounds, and it ignites to a white heat large platinum wires, and may be used successfully for blasting at a distance; and should Government ever adopt any such system of defence as to need the galvanic power, it must supersede the battery in that case. Professor Page demonstrates, by mathematical reasoning, that the new contrivance of the coils affords the very maximum of quantity to be obtained by magnetic excitation.-Report of American Commissioner of Patents for 1844.

NOTES AND NOTICES.

The "satisfactory" Janus.-The Times of Thursday last, in giving an account of a visit of the Lords of the Admiralty to Chatham, states, that their lordships, after inspecting the Dockyard, "proceeded on board the Janus steam sloop, and proceeded under steam down the river, followed by the Black Eagle Admiralty steamer. The rate of the speed of the Janus was about three miles an hour, the wheels revolving about five times in a minute. On its arrival at Gillingham-reach, their Lordships seemed to have had enough of the vessel, for they left it, and proceeded on board the Black Eagle to Sheerness."

Ice-land transformed into Sun-land.-M. Gaymard read to the French Academy of Sciences, at one of their recent meetings, a letter which he has received from Reykiavik, in Iceland, informing him that for an entire year there had been beautiful weather in that island, and scarcely any winter. The summer of 1844, and as much of the present summer as had passed, have been delightful. The meadows are in the finest possible state, and the fisheries highly productive.

Cotton spinning in America.-The Boston Transcript says, "The new cotton-spinning frame, just put into operation at Lowell, we understand, is creating quite an excitement among manufacturers. It is said to require but one half the power, and will make more yarn, and of more even twist, at about two-thirds the expense of the other kinds of frames in use."

An American Locomotive-Poor Oliver Evans's prophecy is being more than realized, concerning the rapidity of transmission by railroads. Perseverance, inventive genius and mechanical skill have fashioned that strong propelling power, the locomotive engine, to almost a state of perfection, and little remains to be done, it would seem, to add to its usefulness, or increase its strength. Of re cent date in their invention, their progress to enlarged usefulness has been almost as rapid as their flight from point to point; and what was but a few years ago a comparatively slow-moving, illconstructed machine, now starts upon its errand with a rapidity and a precision of movement, that seems almost instinct with life. We thought something like this, on Saturday, when looking at a powerful engine, called the "Jacob Little," which was brought down from the city railroad, from Mr. Norris's manufactory, for the purpose of being shipped to the Long island railroad, upon which it is to travel. We were informed that it was built with the purpose of carrying three hundred passengers

and the United States mail from Brooklyn to Greenport, (L.I.) a distance of ninety-seven miles in two hours and a half! and we are assured that the machine could accomplish it in two hours only-a rate of forty-eight miles an hour. Certainly this is speeding upon the wings of the wind. The arrangement of the locomotive differed from others we have seen. In front, the usual four wheeled iron truck, played upon a pivot to permit a free undulatory motion, and next them was a single pair of driving wheels of the unusual dimensions of five feet ten inches in diameter-These two driving wheels supported five sixths of the weight, and immediately behind them under the engine's platform was a pair of small wheels of the same diameter of those of the truck, which bore the remaining sixth of the burden. The relief wheels were not geared to the large driving wheels. The diameter of the cylinder was ten and a half inches, the length of stroke twenty inches, and the whole weight of the Engine almost fourteen tons.-U. S. Gazette.

LIST OF PATENTS GRANTED FOR SCOTLAND, FROM THE 22ND OF JUNE TO THE 22ND OF JULY, 1845.

Robert Addison, of Regent-street, Middlesex, piano-forte manufacturer, for improvements in piano-fortes. (Being a communication from abroad.) Sealed, June 23.

Charles Smith, Newcastle-street, Strand, London, gent., for new and improved methods in the construction and application of a variety of cooking, culinary, and domestic articles and utensils, some of which are applicable to cleaning and a variety of similar useful purposes. June 24.

James Johnston, of Willow-park, Greenock, Esq., for new and improved processes in, and machinery for, making and refining sugar. June 26.

Auguste Cherot, of Nantes, France, spinner, for certain improvements in machinery for spinning flax, hemp, and other fibrous substances. (Being a communication from abroad.) June 30.

Charles Wheatstone, of Conduit-street, Middlesex, Esq., and William Fothergill Cooke, of Kidbroke near Blackheath, Kent, Esq., for improvements in electric telegraphs, and in apparatus relating thereto, part of which improvements are applicable to other purposes. July 3.

David Gavin Scott, of Cromwell-park, Perth, for an invention by which the heddles of a loom are moved to produce various patterns on Woven fabrics. (Being a communication from abroad.) July 4.

James Kite, of Hoxton, Middlesex, coal-merchant, for certain improvements in constructing chimneys, and in the means used for sweeping the same, part of which improvements are applicable to other like useful purposes. July 4.

Patrick Sandeman, of Greenside-place, Edinburgh, for improvements on coffins. July 9.

William Mather and Colin Mather, of Mather Salford, Lancaster, engineers, for certain improvements in boring earth, stone, and subterraneous matter, and in the machinery, tools, or apparatus applicable to the same. July 10.

Henry Pinkus, of Mount-street, Grosvenorsquare, Middlesex, Esq., for improvements in obtaining and applying motive power in impelling machinery. July 17.

Joseph Amesbury, of Devonshire-street, Portlandplace, surgeon, for improvements in apparatus for the relief or correction of stiffness, weakness, or distortion in the human body. July 18.

Thomas William Gilbert, of Limehouse, Middlesex, sainmaker, for improvements in the construction of sails for ships and other vessels. July 18.

Alexander Wright, of South Lambeth, Surrey, for improvements in gas meters. July 21.

*

SIR,-In Vol. xxxix. of your Magazine, p. 309, was given the history of the dredging machine, extracted from Part I. of Weale's "Quarterly Papers on Engineering," in which it is stated that the late Mr. Rennie was the first to propose and construct a dredging machine, to be worked by steam power. "In the year 1802, the late Mr. Rennie, in his Report to the Hull Dock Company on the best mode of improving the docks, proposed applying the six-horse engine, then employed for driving the piles of the coffer-dam of the entrance, to the old dredging machine of Grimshaw. . . . The machinery was fixed in a barge 61 ft. 6 in. in length, and 22 ft. 6 in. in width, and draught of water 4 feet; it worked in a depth of 14 feet until the year 1814, when various alterations were made in it under the direction of the late Mr. Rennie, who caused the sixhorse engine to be erected in it in the year 1804-after which it raised from 20,000 to 23,000 tons of mud per annum, at a cost of about threepence per cubic yard, from a depth of 22 feet." It therefore appears that Mr. Rennie's machine, for which priority is claimed, was proposed in 1802, and erected in 1804; what follows will, however, show that the late Sir Samuel Bentham, in the year 1800 (two years before Mr. Rennie) invented and recommended such a machine to the Lords Commissioners of the Admiralty, which recommendation having been approved of, it was made, and being completed by April 1802, (two years before Mr. Rennie's), was put to work, and found fully to answer the purpose for which it was constructed.

As so much discussion has arisen as to whom the merit of this important invention is really due, I trust that the following details collected from official documents, most of them existing at the Admiralty, together with a description of the machine, and reduced copies of the original drawings from which it was constructed, will be found acceptable to your readers.

It appears, that as early as the year

That is, a dredging machine with buckets, Messrs. Boulton and Watt having only applied the steam engine to the old spoon machine.

1799, Sir Samuel Bentham had directed his attention to this subject, and having collected data on the system of dredging then in use, subsequently devised a machine for performing the operation more speedily and economically; and in the early part of 1800, he addressed the following letter to the Admiralty upon the subject:

"Portsea, April 18, 1800. "Sir,-Among the various inconveniences to which his Majesty's several naval establishments appear to be subject, no one local circumstance seems to cause so much hindrance to the business of them as that of the want of a sufficient depth of water at the wharfs, and other parts of the harbours, contiguous to which these establishments are placed. I have, therefore, been led to consider the laborious operation of digging up ground from under water, as affording an instance in which the introduction of machinery, to be worked by a less expensive force than that of manual labour, would be productive of the most extensive utility."

"The apparatus used by persons under the direction of the Trinity House, seems as well adapted to the digging up ground under water as any engine to be worked by manual labour can be expected to be; but the effect of such an apparatus is so inconsiderable, that the attempts of clearing away by these means some particular shoals in the river Medway have been given up, and though a similar apparatus is, from necessity, now used in Portsmouth harbour, for the purpose of keeping clear the jetties, as well as the entrances to the docks and basins; yet, as the expense of the manual labour alone, for the doing the little work of this kind that is done there, amounts to about 1,4007. a-year, being at the rate of 2s. 6d. per ton, I could not venture to propose the undertaking any considerable works for the improvement of the harbour by any such expensive means.

"At Hull, as well as in Sweden and in Holland, an apparatus for digging up ground from under water has been worked with great effect by means of horses; but the force of a steam-engine being materially cheaper, as well as more convenient, seems far preferable for any such work as this.

By a well-contrived apparatus for this purpose, worked by a steam-engine, I am of opinion that, at a very moderate expense, not only all shoals formed by a gradual accumulation of soil, may be cleared away, to the great benefit of rivers and harbours