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simple diagram, showing the principle of [From the First Report of the Children's Employ. these arrangements for ventilation, without ment Commission, 1842.)

the intricacy attaching to a plan of all the COAL MINES.

ways in an extensive pit, is subjoined from The best mode of ventilating mines hither. Mr. Fletcher's Report, § 20 : App. Pt. II. to discovered is that by means of two shafts p. 822. A is the upcast-shaft. B the down. sunk near each other, perhaps from 12 to 20 cist shaft. The arrows indicate the course yards apart. A stream of air is made to of the air through the underground passages descend one shaft, called the down-cast from the downcast to the upcast shaft; and shaft, and a corresponding stream of air to

the lines drawn from one pillar to another, ascend the other, called the up-cast shaft.

show the trap-doors or partitions which preThe air is set in motion by means of a fire

vent the current of air diverging to the up. which is kindled in the up-cast shaft. A cast-shaft before it has swept the more dis. portion of the air in contact with the fire in tant workings. this shaft, undergoing the ordinary chemical change which takes place in atmospheric air in the process of combustion, is decomposed:

A the nitrogen is separated, and the oxygen uni. ting with the carbon of the fuel, forms carbon. ic-acid gas. Both these gases, as well as the portion of atmospheric air which remains un. decomposed, being heated are expanded, and occupy a proportionally larger space than the same weight of common atmospheric air, and in obedience to the laws of all fluid bodies, are borne upwards, consequently a strong cur. rent of air ascends this shaft; but if a free communication has been established below between the two shafts, an equal current must at the same time necessarily descend the second shaft to fill up the partial vacuum which has been made in the first.

Here then a power is generated capable of As the fresh air that descends the down. forcing a current of fresh air far beyond the cast-shaft passes along the various roads distance to which any mine extends. The through which it is directed, it not only affords great generator of this power is the fire, and the means of healthy respiration to the work. this power will act with a force and steadi. people, but in its course collects and carries ness proportionate to the degree of heat with it every heterogeneous matter which steadily maintained at the bottom of the up it can hold in solution, or which is capable cast shaft.

of being mixed with it, which it conveys out After two shafts have been sunk in a coal. of the mine through the upcast-shaft into the field, the first operation is to establish a air above. The various matters which are communication between them by digging thus conveyed out of a coal-mine in this as. out the coals from the one to the other. cending current are atmospheric air, car. The next is to carry forward a mainway bonic-acid gas, nitrogen gas, carbureted-by. from the foot of each shaft, and then to drogen gas, moisture, and animal effluvia. make a road from the extremity of one In looking at the plans of large coal-pits mainway to the extremity of the other. If there seems to be great perplexity and much a door be now placed in the road which leads ingenuity in the manner in which the air is directly from the foot of the one shaft to conducted to the different parts of the mine, that of the other, the air cannot then pass but the great principle in all is the very simthat way, but must go round along the one ple one which has now been stated, and at mainway across to the other, and thus to the the cost of maintaining a sufficient fire at foot of the shaft in which there is the fire, the foot of the upcast-shaft, and an adequate up which shaft the current must ascend. arrangement for conducting the current of

To whatever distance we suppose the air through the pit, any coal-mine can be
mainways, the sideways and all the other perfectly ventilated,
works of the mine to be carried, communi. Several of the sub-commissioners have
cations may thus be made between them, given detailed descriptions of the different
and by means of doors properly placed, the modes of ventilation adopted in their res.
circulation of the air may be conducted and pective districts.
guided through them to any extent and in From the evidence it appears that in all
any direction that may be desired. A very the districts there are particular mines in

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p. 738).

which, often at great expense to the owners, often been the consequence. Carbonaceons every precaution is taken which intelligence particles from the candles and from blasting, and skill can devise to render the mine and mineral-dust from the working of the healthy and safe ; but that there are great strata or veins, are also suspended in the numbers of mines in which both ventilation air which the miner inspires, and give a peand drainage are grossly neglected, and in culiar character to his expectoration : cope which, as a necessary consequence, there is per has even been detected by analysis in often a frightful destruction of human life. notable quantity in such air (Ibid. $ 30: COPPER, TIN, LEAD AND ZINK MINES. No method hitherto introduced is ade

(Cornish District.)—In proportion as a quate to maintaining the air in the places mine increases in depth, the importance of in which the miners work in anything like ventilation increases, and it becomes at a state of purity; and even in those parts the same time more difficult to effect it in which ventilation keeps up a fair supthoroughly. As far down as the adit level ply of fresh air, there is in almost all there is usually a free perflation, and it is mines a constant smoke after the first blastonly in an 'end,' a cul-de-sac remote from ing in the morning; so that the shafts the shaft, that the air can be materially im. and galleries are not unlike chimneys, often pure. Farther down, as no horizontal com sending out a visible column at the surface. munication with the surface can exist, the The smoke is sometimes so thick (Evidence, interchange of ascending and descending No. 1: App. Pt. 1., p. 822, l. 3) that the currents of air affords the only natural sup miner can with difficulty see his hand. ply; and by making the levels of large size, From the nature of the case, the most ad. and establishing free communication be. vanced point of the excavation must be a tween them by the short levels, called cul-de-sac, and it will often be impossible winzes, aëration (considered sufficient) is to establish any communication with parts effected even in the deepest mine in Corn above or below. Hence it is that almost wall, without the use of air machines. In every miner in the deeper mines is at times fact, those which have been hitherto com exposed to what he himself designates “poor monly adopted are much more advantage- air," by which he means air so impure as to ously applied in the shallower mines or parts affect him in a noxious way distinctly per. of mines. (Dr. Barham's Report, $ 30, ceived by him at the time. Of the less 31: p. 738). To ventilate ends not relieved marked degrees of impurity he makes no by winzes, resort is had to air cylinders, account. of the deficiency of oxygen, the a current being forced through wooden pipes, excess of carbonic acid, the presence of sul. and to falls of water from one level to another. phurous' acid or sulphuretted hydrogen, he

An analysis of eighteen samples of the is not aware, and of smoke, however dense, air from different places in which the men he seldom takes any notice. (Ibid. § 32, are employed, shows an average composition 33: pp. 738, 739). of oxygen 17.067, carbonic acid 0.85, and (Alston Moor District.) -At his place of nitrogen 82.848. The Sub-Commissioner work, however remote, says the Sub-Com. states, “ that in one instance the quantity of missioner for this district, the under-ground oxygen was reduced to 14:51, and in ano. labourer has no air except what comes from ther the quantity of carbonic acid was raised the level by which he has entered. There is to 0·23. These results exhibit a lessening nothing to make a current. Yet some levels in the proportion of the vital ingredient of in this district are half a mile in length, the air from its usual per centage 21, and an some a mile, and one called the First Force increase in a directly noxious ingredient, Level is nearly five miles in length. In carbonic acid gas, from 0.05, its ordinary such a situation “ only slowly, and very amount, calculated to produce effects suffi. slowly, can the air about him, merely by ciently injurious to those who, for hours to. the effect of a difference of temperature wind gether, inhale such a fluid. But the pro. its way upwards, and make room for other portion of deleterious gases occasionally pre air which may penetrate to take its place." sent where the miner must labour (whether Means may be taken to diminish an evil of sulphuretted hydrogen and sulphurous which cannot be removed. Sometimes a acid, which are very rapidly absorbed by the body of air may be forced in by a fall of a water lying in the levels, or of carbonic stream of water from the top surface of the acid, which accumulates, like water, where hill. An opening is made for it to descend there is no drainage), is much greater than down to the level, which it does with great that detected in the analyses here reported. violence, driving a body of air before it, and It is then that the distinctly poisonous ef then it runs out along the bottom of the fects of these agents are produced, and loss level from the mine. of life, either at once or more remotely, has Machines, or fanners, are also used, being

IMPROVED APPLICATION OF THE SCREW TO STEAM NAVIGATION. 473 worked by boys, and the air is carried along from 81.2 degress to 85.6 degrees Fahren. pipes to places to which it would otherwise heit. When the work is in progress, there only very slowly penetrate. Forcing-pumps is, of course, a rapid exchange of oxygen for are also employed to force forward the air in carbonic acid, by means of the respiration a similar way. Sometimes a supply of fresh of the miners, and the burning of the can. air may be got by running a second level dles; and when the blasting takes place, the from the air into the hill, and making a com gases generated by the explosion of gun. munication. In that case the air may be powder are diffused, and a thick smoke fills put in action, and may enter at one level and the shaft. go out by the other. Sometimes a shaft may be carried up to the open air, or let down from the open air into the level; and when that is done a current of air may be IMPROVED APPLICATION OF THE SCREW effected. Whatever is within the range of

TO STEAM NAVIGATION such current, of course, is well ventilated.

Such things, however, are not the general rule. In most mines there are not two levels communicating with the open air, neither can there be shafts from the open air down to the levels. Where nature does not in. terpose a physical impossibility, there is what is equally powerful—the dread of ex. pense. The sum required to sink a shaft or to run a level may be so great that the mine is not worth it. The proprietor would rather discontinue working it than submit to the burthen; and the men, young persons, and boys, having no other means of existence, are eager to be allowed to work at the mine such as it is. (Dr. Mitchell, Report, $ 51, 56 : App. Pt. II., pp. 727,728). TEMPERATURE OF MINES.

(From the same Report.) Coal pits are almost always comfortably warm ; and in general the deeper they are, the warmer. By proper ventilation the heat can generally be so regulated as to render the temperature unoppressive, and even grateful. When cold in the main roads the heat is often oppressive in the side gates and at the workings. Oppressive heat may always be regarded as an indication of imperfect ventilation. It is stated that in the mines of the Yorkshire coal fields the ther. mometer stands in the main roads at from 50° to 60°, in the side roads from 60° to 65°, and at the workings from 64° to 72°. In the deep mines in the northern coal field the temperature is considerably higher. In one of the Hetton pits, in South Durham, the temperature was found to be 66° at the bot. tom of the shaft, and 70° in the workings ; but in the Monkwearmouth colliery, the deepest in the northern coal field the average temperature ranges from 78° to 80°, and Sir,-I make free herewith to send in some parts of this mine it occasionally you some sketches of an application of the rises to 89o.

screw to steam-vessels, which I have al. TIN, corpER, LEAD AND ZINK MINES. ready submitted to my friend, Mr. John

(Cornish District.)—The natural tempe Seaward, and to others, but on which rature of the mines in the south western dis. I should like to have the opinion of trict increases so rapidly, that at the depth some of your intelligent correspondents. of 200 fathoms from the surface it varies The sketches speak for themselves,

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and possibly exhibit nothing new. The a principle that has been deduced from in. shaft placed sufficiently low is meant to ference. The enormous resistance to the move two screws placed longitudinally pressure of a volume of sand through a cy. beneath the water line in midships.

linder or tube is well known; owing to the Sponsings or other contrivances would particles by pressure becoming thoroughly protect them, when in rivers or port,

wedged against the sides of the tube ; but from outward irjury. The screw thus

the effect of the explosion of the powder is

to penetrate through all the interstices, and applied, one would think, must prove

to separate the particles instead of weilging more efficient, ih at the stern of the

them together. vessel, where, besides other difficulties, a

With respect to firing charges by a gal. considerable vacuum has been found to

vanic apparatus, it may be applicable to rerz deprive it of much of its power,

great explosions, but the delicacy of the ar. I am, Sir, your obedient servant,

rangements, and their want of simplicity for FREDERICK SCHERR. use by common workmen, as well as the ex. Kew Green, May 6, 1842.

pense of its application, including that of the portion that must be destroyed at each blast, would preclude its employment under

any ordinary circumstances; its adoption is OPTICAL PHENOMENA,

the less necessary, since so much facility is Sir,-Perhaps some of your scientific given to firing charges either under water or readers will explain the following phe otherwise, and such perfect security from nomena which I have observed.

accidents obtained by the invention of Bick. 1. When a piece of sheet zink is slightly ford's Safety Fuse, an article that cannot be wetted with dilute nitric acid and the too strongly recommended. finger drawn over the plate a most beau

I am, Sir, your obedient servant, tiful transparent blue colour presents it

J. F. B. self, similar to the fine variety of Prus. sian blue ? I have always observed the same phenomenon under the same cir THE ROLLER SUBSTITUTE FOR WHEELS. cumstances.—2. How is it that a reflected

Sir,-- It may be worthy of notice as a image of a candle flame is seen on the matter of historical curiosity that there was carbonaceous film deposit on smoked a patent granted as far back as the 3d of glass, or any other object, when viewed William and Mary (1691), to a person of the at particular angles ?

name of Kendrick Edisbury, for an invention, I am, &c.

having precisely the same object in view

K. DALTON. as that of your correspondent, Mr. George Newark.

Robinson (p. 386 present vol.). As the practice of requiring enrolment of specifications had not at the date of that patent come into

use, it is impossible to say whether Edisbury's BLASTING ROCK-SAND TAMPING-GAL

invention resembled Mr. Robinson's in its

details, but the following extract from the Sir,-In a description of Roberts's galva patent itself will show that the result was nic apparatus for blasting rock, in No. 978

the same. of your Magazine, I find an important error " Whereas, Kendrick Edisbury hath by promulgated with a tone of authority that his humble petition represented unto us, that may lead to a continued perseverance in a with great danger, and much time spent, he very injudicious practice ; I allude to the hath invented and found out a new art or arguments in favour of tamping with dry invention of certain rollers to be used under sand.

the bodies of carriages, carts and waggons It is stated that Mr. Roberts " believes instead of wheels, which will be far more that many hundred weight of gunpowder useful than wheels, ly amending and prewould be required to blow out a column of serving, as well the highways as private sand 2 inches in diameter, and 18 or 20 in. grounds, which said invention was never in depth, placed in a solid rock."

used in England before, and prayed us to Now I will venture to assert, that one grant him our Letters Patent for the sole ounce of gunpowder under such circum use thereof for the term of fourteen years; stances would blow out every particle of the know ye therefore, that we, being willing to sand. The experiment may be easily tried cherish and encourage all laudable endeavours by any one. This mistake has long been and designs of such our subjects, as have by current, and arises from assuming, as fact, their industry found out useful and profit.




able arts, mysteries and inventions, and that WALKER'S WATER ELEVATOR. the said Kendrick Edisbury may accordingly

Sir, I should have answered the letter of reap some fruit and benefit of his labour and charges in and concerning the premises

"W. P." sooner, but I was waiting the arrival of our especial grace, certain knowledge and

of one of my large machines from Messrs.

Ransome's manufactory, which I have now mere motion have given and granted by these

received, and which any of your readers may presents," &c.

see if they feel inclined. It is not so outIt appears further, from Mr. Webster's Patent Cases,* that Edisbury's patent was

rageous in weight as “W. P." would have afterwards the subject of an action for an

us to believe. It is calculated for one or infringement, when a verdict was given in

four men, and weighs only I cwt. 2 qrs., and his favour.

will deliver 50 or 200 gallons per minute, I am, Sir, your obedient servant,

according to the size of the tube. “W.P.”

has so miscalculated and misrepresented an WARDER. invention that he knows nothing of, that

were I to write for one whole year in your Magazine, to prove that it is superior to his

friend “ Centrifugal,” we should, without a MR. WALKER'S WATER ELEVATOR--CHAL fair practical trial, be just where we began,

and your readers no better informed. I LENGE TO THE CENTRIFUGALISTS.

therefore call upon “W. P." to come forSir,-In your Number 981, "W. P." ward in an honest straightforward manner, states, that with a proportionate power his and substantiate the challenge which he has centrifugal pump will do five times the made in the Mechanics' Magazine, May 28. work of Mr. Walker's machine for raising “ W. P." may have the choice of height water. I wish to know whether I rightly un from 10 feet to 50, and the trial to come off derstand him to mean that, with the same within a month, before practical men, for no power applied to each, in the same time, the less a sum than 1001. Perhaps, Mr. Editor, centrifugal pump will raise five times as you will favour us with your presence, as much water? I find that Mr. Walker's the trial must be on the banks of the Thames machine raises one-third more water than for the convenience of scientific men residing my old one with the same power in the same in London. space of time. In fairness, therefore, to all When all this has been done, then Mr. parties, I should like to see this centrifugal “W. P." may reason with certainty, and pump in action. I do not know how it acts,

your readers be in a position to judge for but if “ W. P." will show me that he can themselves. at the same expense, or first outlay, affix an

I remain, Sir, your most obedient, apparatus to raise fluids, say 30 feet, in the

J. WALKER. same space of time (say one hour,) with the same power (say one man), and raise as King William-street, City, June 8, 1842. much as one-tenth more than I do with Mr.

(We shall willingly be present at the proposed Walker's apparatus, then “W. P.” may

trial; but we should like to see the money part of hear of something to his advantage. On his

the wager abandoned. The triumph of truth ought acquainting me (by a note addressed to your to be triumph enough to either party.--Ed. M. M.] care,) when he will be prepared to exhibit his centrifugal pump in action, I shall immediately adopt means to test the comparative efficiency of the two instruments-not by a private, but a public trial in the pre

SWIFTsure' STEAMER AND BLAXsence of scientific persons—the results of

LAND'S PROPELLER. which, whatever they may be, shall also be

Sir, -The tremor you remarked when on made known to all the world.

board the Swiftsure, immediately above the I am, yours, &c.

propeller, is wholly removed when the ves. T. Y.

sel is properly trimmed. The motion, howJune 3, 1812.

ever, is so slight, and at the same time, in P.S. I have sent a copy of this to Mr. so unobjectionable a place, that I feel scarcely Walker, who will give my address--and who justified in troubling you with these few lines is quite agreeable to my proposal.

respecting it.

I am, Sir, yours faithfully,
A new work in course of publication by the

F. COLLIER CHRISTY. learned anthor of the “ Law and Practice of Patents," the best book on the subject which has yet Hatcham Manor House, June 4, 1842. appeared.-ED. M. M.


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