since that some person at Paris had applied a current of air to one of the strings of a piano to continue its vibrations. The string, under these circumstances, may be considered as a reed or spring-valve of an instrument of the free-reed kind, only it is fixed at both ends instead of one only; but it still acts as a reed. A violin string might be made to do so likewise; and this arrangement appears to possess the advantages of combining the sounds which result from the alternate emission and stoppage of air with those resulting from the vibrations of a sounding board or belly, and if this can be effected, a considerable incréase of power, and change of the quality of the tone may be expected. Such an instrument, like the sostinente piano, would possess the rapidity which is peculiar to instruments of percussion, the vibrations originally produced by the blow of the hammer being continued by the impulse of the issuing air on the string; but I apprehend the power of swelling the sounds by the pressure of the performer's finger, which is the great charm of such instruments as the harmonicon, the celestina, the claveol, the odephon, or the sostinente piano of Mr. Mott, could not by any contrivance be conferred on it. Might not, however, the effects resulting from a command over the pressure of the wind be made available by means of pedals, as it is in the eolophon, and other instruments of the same kind? But all such instruments must, like the organ, be inferior in expression to those whose sounds are caused or sustained by friction, directly or indirectly applied to their string, or other vibrating parts.

I remain, Mr. Editor,
Yours, respectfully,

ALFRED SAVAGE.

16, Garlic Hill, July 1, 1842.

BLASTING OF ROCKS BY GALVANISMAPPLIED TO THE REDUCTION OF A WATER FALL ON THE NORTH ESK.

Sir, I observe in your Magazine for last month, No. 983, some strictures on the account of Mr. Roberts' mode of "Galvanic Blasting," detailed in a preeeding Number. Will you permit me to offer a few remarks on the subject?

"J. F. B." objects to sand-tamping

of "

as an error, and states that the effect of an explosion on a column of sand is very different from that of a blow; inasmuch as the explosion penetrates into the interstices, and by means of its action on the included air will blow out the sand with great ease. In this view, sand must be the very worst of all tamping stuff. Now, I apprehend we have here a case Theory versus Practice," for, in reality, sand makes excellent tamping. There must therefore be some flaw in the theory. There can be no doubt of the tendency of the explosion to condense the interstitial air, or of the air, if thus condensed, to throw out the sand; just as would happen if it were mixed with gunpowder throughout. I question, however, if this really ever happens. In a column of fine sand, either quite dry or thoroughly wet, the particles lie so closely together that the interstices are very small; they are at the same time separated by surfaces, so innumerable, so varied in their direction, and offering so much resistance from friction to the passage of the air, that long before the effect of the explosion has reached the interstices, the surrounding rock is rent asunder.

In point of fact this is the case; sand may, for aught I know, be blown out, if placed in circumstances where it is impossible for any thing else to give way, but I have never found it so; the rock has always yielded in preference, even where masses of granite of many tons weight had to be torn off by the explosion.

Of the superiority of galvanic ignition to any kind of fuse there can be no question; the fuse does not entirely prevent waste by the vent-hole; it is inapplicable under water; and it does not permit the simultaneous firing of several charges. When blasting is required only occasionally, or very small charges are used, it may not be worth while, or economical to apply the galvanic discharge; but wherever blasting is constantly required, and charges of even moderate size, as in granite, whinstone, &c., it will be found highly economical. The expense is 4d. each charge for cartridge and wire discharged; while the saving of gunpowder, especially with simultaneous firing, will be from one-third to one half of what is usually employed.

I can speak of the galvanic discharge

with the more confidence, having recently had it constantly in use in blasting under water. The operation was the reduction of a waterfall on the North Esk, belonging to Lord Panmure, with the view of rendering it accessible to salmon. The work had previously been abandoned as impracticable and dangerous. By this means it has been speedily and safely accomplished. The apparatus used, differed from that recommended in Mr. Roberts' pamphlet, in the absence of cells in the battery, and of binding screws on the main conductor, which was insulated by common twine. These differences render the whole working so simple, that a workman may acquire a knowledge of it in a single day's practice, and, if properly made, the apparatus is not liable to go out of order.

I am, &c. &c.

JAMES T. WILSON.

Glasgow Mechanics' Institution, July 9, 1842.

ECONOMICAL

APPLICATION or STEAM

POWER TO THE MOVEMENT OF WATER
WHEELS, AT WHEAL UNY. BY CAPT.
TREGASKIS.

[From a description of a model of the machinery employed at Wheal Uny, given in the Transactions of the Royal Cornwall Polytechnic Society-Ninth Annual Report.]

The model represents a large steam engine, pumping water to work water wheels, for various purposes, but chiefly for breaking and pulverizing rocks of tin stuff.

The water drawn up by the steam engine from the bottom to the top of Wheal Uny hill, forms two separate mill streams, and after turning all the wheels in its course, returns again to the engine shaft, through an adit at the bottom of the hill, and is again drawn up for the same purpose. The same water turns the same machinery an indefinite number of times, as long as the engine may continue at work; the waste and evaporation being supplied from the bottom of the mine. Thus one and the same steam-engine drains the mine of water, pumps up additional water from the adit, draws up all the stuff broken from the lode, breaks it down to a proper size for stamping mills, and these stamping mills pulverize the whole, in order to separate, cleanse, and make the ores merchantable.

The model represents machinery actually in use.

The steam-engine at Wheal Uny is represented by its type on the platform pumping water. The first wheel turned by the water, and which stands on the same platform with the steam engine, works a whim-engine for drawing stuff. The groove in this machine in which the chain is wound up, has a vertical position. The second wheel works another steam engine, which has the groove for winding up the chain in a horizontal position. The third wheel works a large hammer, for breaking down the large stones to a proper size for the stamping mills. All the other wheels work stamping mills to pulverize the ore.

The model is intended to show the mode in which steam power may be applied, with advantage and economy, to stamping mills by water, as the medium of communication between the first mover and the stamping apparatus, instead of the crank. The mode of applying anti-friction wheels, under the large water wheels, in the simple manner in which they are fixed at Wheal Uny is also shown.

The application is new both in the mode of communicating steam power, and fixing anti-friction wheels under large water wheels for stamping mills.

The application of steam power to water wheels, was first employed in this manner as a substitute for the crank, at Wheal Vyvyan, by myself, under the patronage of Mr. Charles Fox.

And

It may be asked, What advantage is gained by the mode adopted at Wheal Uny? In reply to this I would say :-It is an acknowledged fact, that pumping engines do more work by the consumption of a bushel of coal, when unconnected with the crank, than it is possible to do in connexion with it. we have found by experiment, that more work is performed by pumping water over wheels, than can be done by the steam engine through the medium of the crank, when connected either with the winding, or stamping apparatus. Wheal Uny engine, last month (July, 1841), pulverised fourteen sacks of very hard tin stuff through a fine grate, with a bushel of coals, each sack containing twelve gallons; this exceeded the best stamping engine in the county; very few steam stamping mills do as much as ten sacks, with a bushel of coals. Wheal Uny steam-engine lifted about seventy-six million pounds weight one foot high, by the consumption of one bushel of coal, through the whole of last month (July).

B

The plan represented in the prefixed engraving was submitted to the Senate of Hamburgh, by the Consul-General, J. Colquhoun, Esq., on the 11th of June last, accompanied with the following explanatory description by the designer.

I am convinced that if accidents by fire are to be avoided, in densely-populated cities and towns, and if the authorities of such places are really desirous that the inhabitants shall enjoy the full benefit of breathing an atmosphere as pure as possible, no other plan can be devised equally effective as the one now laid before you, for securing this twofold advantage.

In regard of economy and safety, every well-informed person will readily understand, that if instead of ten fires, only one were to be in operation, and that so con

structed as to preclude the possibility of setting the chimney on fire, even by authority or incendiarism, then four-fifths at least of fuel would be saved, and the danger from fire diminished nine-tenths. It will further be clear, that if it should so happen that a fire were to occur from casualties unconnected with the fireplace, and if the inhabitants were so unfortunate as to make the greatest blunders in their attempt to extinguish it, not more than one square could possibly be damaged. Even this, however, would never happen to any very serious extent, as every house would constantly have at command, an abundant supply of water, sufficient to extinguish any fire that might occur, from whatever cause.

I believe that 180 squares, as B B, besides the large Exchange square E F, in

the centre, are more than requisite for the comfortable accommodation of the houseless families of Hamburgh. Ten houses of 18 feet each, a a, in front, will make 180 feet frontage on each side of a square, forming the streets. Each corner building will have two fronts suited to purposes requiring such a position. The extent of frontage of the houses may also be varied in accommodation to the necessities or convenience of the intended occupants of the buildings respectively. If the houses be 30 feet in depth, the interior square will be 120 feet. If we take 20 feet for the width of the road c c, to the warehouses bb, and 20 feet for kitchens or cellars, 10 feet on each side of the square, there remains on each side of the road to the warehouses, a space 40 feet wide, by 100 feet in length. If this space be divided into five equal parts, we find it might be occupied by 10 warehouses, 5 on each side of the road, 40 feet long and 20 wide.

The warehouses should be erected on the squares nearest the Elbe. I think they would also be best situate in the centre of the squares, on account of the nuisance to the public of loading and unloading in the public thoroughfares.

Other squares may have exhibition rooms, lecture rooms, school rooms, manufactories,counting-houses, shops, shambles, and all sorts of markets, stables, pleasure-grounds, or theatres of amusement, &c. &c.

Four pleasure squares, D D D D, should be merely enclosed with railings, without any erection or buildings.

All the interior squares should be covered with the flat roof, invented by me, in 1824, and which was used on the Royal Palace at Berlin, thirteen years ago, and has proved perfectly satisfactory. When the advantages of this superior flat roof are fully understood, and duly appreciated by a discerning public, there is no question it will entirely supersede all other roofing now in existence. It requires but little wood-it is therefore more economical than other roofs; and it is so simple in its structure, that every workman can place it. It can be transferred from one building to another, without the least damage to the plates, forming such roof.

If economy in fuel be of importance to the inhabitants, each house may be warmed by the kitchen fire alone. This I have several times proved in London. Every

room, whatever its use, will be well ventilated by such continual change of air, both by day and by night, throughout the year, ensuring warmth in winter, and coolness in summer, without any machinery,-pots, pipes, bowls, &c. All fire-places constructed and erected in accordance with the principles of my new science in natural philosophy, will be entirely free from the usual defects; and no building can be endangered by the requisite apparatus.

Every manufactory, warehouse, stable, closet, drain, or other necessary openings, must have free ventilation (conducted without machinery or the use of fire, by the physical, chemical, and mechanical powers of nature) to prevent any noxious vapour from mixing with the air in the streets. These poisonous exhalations should be conveyed away without unsightly flues, &c. This my new and exceedingly useful invention will prove the best means for keeping the air always pure and wholesome, in towns of every description of buildings.

All buildings requiring light by night should be lighted up with gas, in accordance with the principles of my new science, so that not the least danger will exist of explosion in the buildings so lighted, agreeably to my English patent method of gas-lighting. The noxious vapour from the flame is not allowed to intermix with the atmosphere in the rooms, but conducted away into the open air, on the outside of the buildings. This light consumes 30 per cent. less gas than the gas lights in general use in London.

Should this my plan be adopted, I propose having two, or not exceeding four water cisterns erected in each square; the whole so arranged that every room shall have a water-cock, and the watercisterns and pipes be secure against the most intense frost of the coldest winter.

The principal square, containing the Exchange, in the centre of the town, is proposed to be 400 feet on each side (if space will permit), and four buildings, FFFF, in the centre of this square, will occupy a space of 200 feet square, uniform in frontage, and 50 feet deep, leaving a central square of 100 feet for the Exchange, E. These buildings may have apartments suitable for a senate, courts of justice, consistory and university (if required) library, halls, concert rooms, ball rooms, &c. &c.

To the Exchange buildings, as also to

the Exchange itself, there will be four entrances, by means of a flight of steps situate in the centre of each front. The Exchange will have a skylight.

It is not easy for the public to judge between true and false science, as the community are so often deceived by men of science as well as by empirics in philosophy. I therefore think it my duty to subjoin a few of the very numerous unexceptionable testimonials I possess, from ministers of state and scientific men of exalted rank, in London and on the Continent.

F. A. BERNHARDT, &c. &c.

20, Crosby Hall Chambers,

Bishopsgate Street.

66

[Subjoined to the preceding statement are certificates from the Prussian Ministers, Schuckmann, Maltzahn and Schoning, the Prussian Ambassador Bulow, and several other subordinate functionaries of the Court of Berlin, all of a very favourable character; these are followed by others even more so, from Charles Barry, Esq., the Architect of the British Houses of Parliament; Joseph Hansom, Esq., the Architect of the Birmingham Town Hall; Dr. Nathaniel Grant, and Dr. A. Toulmin. Mr. Barry says, "From the experiments I have made and the evidence of others, I believe that any degree of warmth may at all times be obtained by means of the stoves which he (Mr. Bernhardt) has erected." Mr. Hansom thinks Mr. Bernhardt's "stove perfect," giving 66 a warm and salubrious air and acting as a perfect ventilator." Dr. Grant pronounces it more likely than any other he has seen to produce the effect of keeping the air in a room wholesome." And Dr. Toulmin says, "the points of excellence are, that a house thus warmed, is constantly supplied in every part with a pure and warm atmosphere of any given temperature, whilst the air, vitiated from having been breathed, is constantly carried off, and thus a continual aërial circulation is established." These are strong testimonials; but the readers of the Mechanics' Magazine cannot be expected to have forgotten that it contained, some three or four years ago, others of a different description. We must refer in particular to an elaborate paper by Dr. Ure, which appeared in our 28th vol., p. 273, and to which we have never seen any satisfactory answer. We question much, however, whether Mr. Bernhardt's system has suffered so much at the hands

of any person, as it has done at his own. His tone in speaking of it has been always one of extreme mystery. He is fond of referring, as he does, in the communication which we now publish, to "my new science in natural philosophy;" but he has never yet, to the best of our knowledge, stated plainly what "my new science" is. We have heard, that when asked to explain the rationale of his system to a Committee of the House of Commons, he declined, on the ground that that was his affair, not theirs! It is not by corking up one's mouth in this way, that patronage and support are to be obtained in this country; neither is this the way in which true science usually manifests itself. If there is really any thing good in Mr. Bernhardt's systemand it is difficult to believe that there are not some good points in what such men as Barry and Hansom have so decidedly approved-Mr. Bernhardt must enable the public, by a full and unreserved disclosure of particulars, to form their own judgment upon it, or make up his mind for the general neglect, which will be the inevitable, and then not unmerited, consequence. ED. M. M.]

THE CRANK QUESTION.

Sir, I did not see your correspondent "M.'s" first answer to my last letter till February, although it was in your October Part, and expecting shortly to proceed homewards I put off answering it until I should be on my return; this was delayed from various causes till April, when his December letter arrived, so I now sit down to answer both, hoping to be the bearer of my own letter.

state.

It appears to me, that in his last letter, "M." has so completely annihilated his original experiment, and the conclusions he considered himself justified in drawing from it, that I need scarcely have noticed it again, had he not very coolly, a little further on in this same letter, told us, that his arguments were as sound as ever! I shall therefore endeavour to open his eyes to their true He tells us (vol. xxxv., p. 259), "The work performed in the experiment when 37 lbs. was in motion, is represented by the number 149." And in his second letter, (page 470), he says that the 50 lbs. weight only moved 2.7, when the 37 lbs. moved 4 inches, and therefore, that "the power actually expended" in this case, "was 2.7 x 50 135 only.' In this experiment then, as far as it went, I presume your cor