66

Example. If 1000 cubic feet, say at 50° of Fahrenheit, were pressed by the engine in a given time, and heated to 600° of Fahrenheit, it would then be increased in volume to 2104.4, and so on for every thousand feet that would be blown into the furnace. In prosecuting the experiments which this idea suggested, circumstances became apparent to me, which induced the belief on my part, that heating the air introduced for supporting combustion into air furnaces, materially increased its efficiency in this respect; and with the view of putting my suspicions on this point to the test, I instituted the following experiments :

"To the nozzle of a pair of common smith's bellows, I attached a cast iron vessel heated from beneath, in the manner of a retort for generating gas, and to this vessel, the blow-pipe, by which the forge or furnace was blown, was also attached. The air from the bellows having thus to pass through the heated vessel above-mentioned, was consequently heated to a high temperature, before it entered the forge fire, and the result produced, in increasing the intensity of the heat in the furnace, was far beyond my expectation, and so evident as to make apparent to me the fallacy of the generally received opinion, that the coldness of the air of the atmosphere in the winter months, was the cause of the best iron being then produced.

"In overthrowing the old theory, I had, however, established new principles and facts in the process of iron making, and by the advice and assistance of Charles Macintosh, Esq., of Crossbasket,* I applied for and obtained a patent, as the reward of my discovery and improvements.

66

Experiments on the large scale to reduce iron ore in a founder's cupola, were forthwith commenced at the Clyde Iron Works, belonging to Colin Dunlop, Esq., which experiments were completely successful; and, in consequence, the invention was immediately adopted at the Calder Iron Works, the property of William Dixon, Esq., where the blast being made to pass through two retorts placed on each side of one of the large furnaces, before entering the furnaces effected an instantaneous change, both in the quantity and quality of iron produced, and a considerable saving of fuel.

"The whole of the furnaces at Calder and Clyde Iron Works were in consequence im

*The patentee of the caoutchouc manufacture so well-known by his name.-ED. M. M.

mediately filled (fitted?) up on the principle of the hot blast, and its use at these works continues to be attended with the utmost success; it has also been adopted at Welsontown and Gartshirrie Iron Works in Scotland, and at several works in England and France, in which latter country I have also obtained a patent.

"The air as at first raised to 250° of Fahrenheit, produced a saving of ths in every ton of pig-iron made, and the heating apparatus having since been enlarged, so as to increase the temperature of the blast to 600° Fahrenheit and upwards, a proportional saving of fuel is effected; and an immense additional saving is also acquired by the use of raw coal instead of coke,which may now be adopted. By thus increasing the heat of the blast, the whole waste incurred in burning the coal into coke is avoided in the process of iron making.

By the use of this invention, with ths of the fuel which he formerly employed in the cold air process, the iron-maker is now enabled to make 3rd more iron of superior quality.

"Were the hot blast generally adopted, the saving to the country in the article of coal would be immense. In Britain, about 700,000 tons of iron are made annually, of which 50,000 tons only are produced in Scotland; on these 50,000 tons, my invention would save in the process of manufacture, 200,000 tons of coal annually. In England, the saving would be in proportion to the strength and quality of the coal, and cannot be computed at less than 1,250,000 tons annually; and taking the price of coals at the low rate of 4s. per ton, a yearly saving of 296,000l. sterling would be effected.

"Nor are the advantages of this invention solely confined to iron making; by its use the founder can cast into roods an equal quantity of iron in much less lime, and with a saving of nearly half the fuel employed in the cold air process; and the blacksmith can produce iu the same time 3rd more work, with much less fuel than he formerly required.

"In all the processes of metallurgical science, it will be of the utmost importance in reducing the ores to a metallic state."p. 81.

This interesting narrative, combined with the report of M. Dufrenoy, on the hot blast system, a translation of which appeared in the Mechanics' Magazine for 1835, presents a complete view of the history and advantages of the discovery. As to the amount of the latter, differences of opinion still exist, and may be expected to exist, until the unerring

process of actual experience shall have determined the relative strength of the hot blast and cold blast iron. But, whatever these differences may be as to the degree of importance attached to Mr. Neilson's discovery, there can be none as to its great utility and merit generally, and as little with regard to the simplicity and interest of his history of its progress from conception to execution.

There is another point of difference among engineers, on which we have a paper in this volume;-the duty performed by the Cornish pumping engines. The paper is contributed by Mr. Wicksteed, who was commissioned by a London water company to examine the engines in question, and make his report, both as to the reality of their performances, and their adaptation to the usual purposes of water-works engines. Mr. W.'s opinion is favourable on both these heads. As to the former he has no hesitation in making up his mind, after stating the performances of the engines he actually saw at work, he adduces the various reasons which lead him to believe that, even if the parties concerned were inclined to resort to deceptive practices, it would be impossible to carry their intentions into effect:

"But supposing, for the sake of argument, that the engineers, and the agents of the mines, were so disposed, and could get these gentlemen (the coal-agents) to combine with them for the purpose of making a false report, the insanity of such a proceeding will, I think, appear evident on a perusal of the following statement :

"The engines is Cornwall are designed, the drawings made, and the construction and erection of the machinery superintended, by gentlemen who are appointed as engineers to look after the machinery of the mines. The castings are made, and the work designed by the said engineers is executed at two large foundries,' or engine manufactories at Hayle.

"There are more than twenty engineers employed in the mines in Cornwall, all of whom are anxious to construct the best engine, as the parties producing the engines that do the most duty obtain, of course, the most employment. It is therefore a matter of jealous attention on the part of these gentlemen to take care that no engine shall have undue credit for doing the most work. It happens occasionally, where a great improvement has been made, that doubts are

das to the accuracy of the reported

duty in such cases the engineers and agents of the other mines call upon the parties whose engine is reported as performing extraordinary duty, to allow them to prove it; this call is answered by fixing a time for the trial-the trial lasts for two or three days, during which time the engine is in the hands of the rival parties, who are on the watch to detect unfair play, if any should be attempted. If the result of this trial is favourable, the party in question receives due credit; if otherwise, his character as an honest man is lost. If this is not as severe a test of the accuracy of the reports as can be made, and not sufficient,-then, indeed, prejuce must have its full swing, and no further proof can be given, as gentlemen going into Cornwall from London and elsewhere, for the purpose of proving the truth of the statements made by the Cornish engineers, may with equal justice be charged with making false reports."-p. 120.

With respect to the question of applicability and relative economy, Mr. Wicksteed's tone is equally decided: he winds up his paper thus:

"In conclusion, I beg to observe, that if the Cornish engines do the work that it is stated they do, and if they are applicable to water-works purposes, of both of which I have no doubt, then the saving is most important; for supposing instead of three engines, consuming 3,000 tons of coals per annum, one could be erected doing the work of the three, and only consuming 1,000 tons, assuming the price of coals delivered to be 188. per ton, the saving in coals alone, without reference to the savings in the reduced number of engine-keepers and stokers, the current expenses of one engine instead of three, the wear and tear of machinery, and buildings, would be 18007. per annum."-p. 130.

Mr. Wicksteed's paper is almost immediately succeeded by another referring partially to the same subject; a communication from Mr. Seaward, on the system of boring for " artesian wells" especially as applicable to the supply of water to cities and towns. Mr. S. gives his voice most decidedly against resorting to this method, except in situations where the two more natural sources of supply, running streams and rain-water, are not accessible. opinion is fortified by reference to sundry cases of failure in the object sought, after great expense incurred, which would have been far more forcible had Mr. S. favoured his readers with fuller particulars, especially as to locality,

The

which, at present, they are left to guess at from very slender data. Mr. S. after several instances of this unsatisfactory character, sums up this::

"We could add many other instances of the total failure of what is called the simple boring system; of works begun and never finished to any useful purpose of others pertinaciously carried on for four or five years, until the patience and the funds of the parties were alike exhausted; but we think enough has been stated above to prove to your satisfaction how very uncertain has been this method of obtaining water. We think it right, however, to guard against the impression that boring for water is a bad system; on the contrary, allow us to repeat that we think most highly of it; but then only under proper management, and as a useful auxiliary to the sinking of capacious wells.

"With respect to the project generally, of forming a regular establishment for the purpose of supplying water to the various towns of France, we have to remark, that there can exist no physical impediment to the accomplishment of the plan; there is no question but every town in France might be made to enjoy the same inestimable advantages possessed by the inhabitants of London and other towns in England: that is to say, a constant, abundant, and an economical supply of good water, for all purposes of domestic and manufacturing

use;

but of the three modes by which this can be accomplished, boring or well-sinking is decidedly the most expensive, and the most uncertain in the final results."-p. 150.

Does not this last paragraph abound overmuch in phrases of a conventional character ? The supply of water to "London and other towns in England" may be vastly superior to that enjoyed by the towns on the continent, but we question whether it can, unless comparatively, be termed an "abundant and economical supply" of "good water." Mr. Seaward's own narrative itself would seem to point to a different state of things. The manufacturers, of whose efforts to obtain a supply on their own premises he tells us, must be mad indeed, to run to so great an expense and incur such an infinity of trouble in the attainment of an object which according to him, is already within their grasp! The truth is, they find to their cost, that the supply is by no means "abundant," and far, very far indeed from "economical," while an additional motive to persevere in "boring for water"

VOL. XXVIII.

at any expense and risk is constantly given by the operation in various ways of the grinding monopoly of the great companies which hold under their control the supply of one of the prime necessaries of life. As to the "goodness" of the water in London, the least said the better, when it is considered that it is chiefly procured from that great common sewer, the Thames, after it has received the filth of the greatest portion of the greatest city of the world into its bosom, it must be obvious that to talk of its purity would be ridiculous. It is true, that the inhabitants of a large section of the capital are comforted with the idea that their supply is free from the taint, and that they derive the wholesome element from the great work of Sir Hugh Myddleton: but this is a mere delusion. The little canal which might hope to supply the London of James the First's time, could hardly hold out against the demands of the London of the present day, even in its palmiest state, much less in the droughts of summer, when its stream (?) is reduced to a mere runnel. To make up for the deficiency, old father Thames is resorted to, and that part of the supply which has just run to waste down the sewers stands a fair chance of being made to do duty again, and so on ad infinitum,—in company with whatever other matter it may have met with in its progress through the minor receptacles of filth to the great receptacle of all. That by this process the fluid furnished, soon ceases to be "good water," a convincing proof is offered by the stench emitted from the compound in a short time after its being

66

abundantly" supplied. If there is no easy way to remedy the evil, as Mr. Seaward assures us, so much the worse; but, in the meantime, while "such things are," let him refrain from boasting of the " inestimable advantages" of the existing system.

Many of the remaining contributions in the volume are of the highest excellence, but we have not space to notice them as they deserve. Among the most prominent are, an account of the construction of the Lary Bridge, near Plymouth; some experiments on the expansion of water by heat, by the late Mr. Tredgold; a very long collection of tables of the velocities attained by boats on canals, furnished by Mr. Macneill,

diameter, it would be necessary to raise the edges at the ends also, which is shown by fig. 2. It will very naturally be asked by persons not conversant "What use with practical mechanics, is it to give forms of machinery which are either impracticable in the arts, or at least not formed with sufficient facility to enable the artisan to compete with the known methods?" In answer I would say, that the boiler-plate with two raised edges can be rolled of that form with as great ease as without them, by simply cutting a small portion of the roller away at each end as shown by fig. 3.

A d

Fig. 3

D B y

C, D, the highest part of the roller for forming the thinest part of the plate, and A, B, the further ends for raising the edges A, B, C, D, of the plate fig. 1. The ends y, and x, are the axes upon which the roller runs. When it is required to roll the plate of fig. 2, having raised edges all round; it becomes necessary to alter the roller a little, and it would also require a considerable deal more attention in the workmen in placing the

The

This

C, D, the highest part of the roller for forming the central or thinest portion of the plate. A and B, the places cut down to raise the longitudinal edges A, B, C, D; and x, y, the axes on which the roller turns as shown before. only difference between this figure and fig. 3, being in the part E, G, which is cut away until the bottom of it becomes level with the parts A and B. groove is made for the purpose of raising the end edges of the plate A, C, B, D, fig. 2. It is obvious that the diameter of this roller must be a given quantity, so that the groove E, G, may form the two end edges at the required distance, and for that purpose the circumference of the roller, without the groove E, G, must be equal to the length of the thin part of the plate. W. ETTRICK.

Sunderland, Dec. 5, 1837.

Telegraphic communication by vision appears likely ere long to be superseded -if we may judge from the interest excited by the various rivals which have lately risen to the established mode. Electricity and sound have been for some time prominently on the tapis-both of them old ideas, and now water is brought forward, and that not for the first time either, as Mr. Vallance experimented upon it some twelve years ago. The

following description of Mr. Whishaw's telegraph appeared in the Times:

"A novel and ingenious method of conveying intelligence from one place to another has been lately invented by Mr. Francis Whishaw, of South-square, Gray's-in, in which place there is now a model of the contrivance. The principle on which the process is carried on depends on the wellknown fact of water always finding its own level (unless under circumstances where