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I thank you a thousand times, my dear Sir, for all the trouble that I give you, and I pray you to accept my lively gratitude.

DAGUERRE.” “ Bry-sar-Maine, 5th July, 1841.”

THE ARTESIAN WELL OF GRENOBLE.*

Ar Grenoble, in the vicinity of the French capital, it was considered advisable some years ago to endeavour to procure good water by means of an Artesian well. M. Mulot d'Epinay was the engineer to whom the task was entrusted. On the 31st of December, 1836, the bore had been carried, after immense labour, to the depth of 383 metres (a metre is 3 feet and 2-10ths English). The soil was a clay, very hard and compact. In the month of June, 1839, the bore had reached the depth of 466 metres, and the soil was still a bed of clay, though a variety of strata had been previously passed. M. Mulot kept a regular journal of observations, relative to the soils and strata penetrated, and the temperature at different depths. This record will be valuable when published. At length, after a task of seven years one month and twenty-six days' duration, M. Mulot was rewarded by a degree of success proportioned to the time and trouble expended. Water was not only found, but found under such circumstances, and in such quantities, as will cause the well to be one of the most useful works, as well as one of the greatest marvels of artistical ingenuity in France. The fluid burst out in a perfect torrent, rising to the surface of the bore to the amount of nearly three cubic metres in a minute, or 180 metres in an hour, and 4320 metres in the twenty-four hours. Such is the force with which it flows

up the shaft, that it mounts more than thirty-two English feet above the surface of the ground. M. Hemery, director of roads and bridges, has calculated that the force of ascension of the water, at the bottom of the shaft, exceeds, by fifty times, the force with which water rises in a vacuated tube of thirty-three feet. The orifice of the well is fifty-five centimetres (about one foot eight inches) in diameter, and at the bottom it is eighteen centimetres in diameter. The shaft is in all 547 metres (or 1630 French feet) in depth, and the sides are strongly plated with iron to a depth of 539 metres. The dome of the Invalids, which has an elevation of 300 feet above the ground, is thus only about a fifth of the perpendicular measurement of the Artesian well of Grenoble.

Three times, during the operations, did the shaft give way, but the indefatigable engineer was not daunted, and at last he has had his reward. The water, which the well pours forth incessantly, has converted one of the neighbouring streets into a river, but the workmen are at present employed in forming a channel for its proper con

Mining Journal.

veyance from the spot. As might be expected, the fluid was at first mixed with sand and earth, and continued to be so for some time. It is perfectly sweet, however, and had no odour of a disagreeable kind, or any other deteriorating qualities. It is of such a temperature that there is an obvious smoke arising from it when it reaches the surface. This is a feature not likely to continue, and indeed easily removable before use. The whole cost of this great work of art to the city of Paris is said to have been 160,000 francs. The perseverance in this labour for such a period of deferred success, is to be ascribed to the confidence resulting from modern geological discoveries ; and the value of these is most splendidly shown by the success attained. By an ingenious contrivance, M. Mulot has been able to raise large quantities of sand from the bottom of the well; thus clearing the water more rapidly, and also adding very considerably to its force and volume. This removal of the sand has been attended with curious consequences in more respects than one. After ceasing, in a great measure, to throw up sand, the well has begun to throw up shells and petrifactions of various kinds, the debris of a former world. The success of the operations of Grenoble has also induced engineers to make similar attempts in other quarters. One is begun on a large scale at Vienna.

WHIRLWIND IN Liverpool.-On Thursday, May 11, at halfpast three o'clock in the afternoon, the inhabitants of Bond-street and the lower part of Burlington-street, were thrown into a complete state of excitement and amusement by the occurrence of a whirlwind. The empty space of ground between the two streets is a hollow, of about twenty feet in depth, and is much used by the inhabitants for drying clothes, for which purpose posts are fixed in the ground at convenient distances, to which lines are attached. At the time above-mentioned, the hollow was completely filled with clothes, drying upon the lines ; for some time previous there was not a breath of air, when all of a sudden it began to blow very hard, and what appeared strange was, one part of the clothes streaming out in one direction, and another part the contrary way. In a short time the currents met, and the lines were almost instantly stripped ; some articles of clothing were carried in a straight line upwards to an altitude of about 500 feet, when they seemed to have got into a different current from that of the smoke of the neighbouring chimneys, the latter blowing southward, while the clothes were carried away in a northerly direction, and they have never since been heard of, at least, by the owner.

ELEMENTARY LECTURES ON ELECTRICITY, &c. .

LECTURE XVII.

manner.

In persuing our illustrations on the electro-mechanical agency in the production of certain effects, it may not be amiss to employ different kinds of bodies in the circuit, in order to show how they are differently affected by modifying the mechanical action in the discharges of similar quantities of the electric fluid upon them.

I will, for instance, place a small loose ball of tow between the balls of the universal discharger, and discharge upon it a large Leyden jar, from a high degree of intensity. You observe that the tow, although an inflammable body, is not ignited; but several of its fibres are broken, and it is somewhat flattened by the mechanical action of the discharge.

Now, although the tow bas escaped conflagration in this case, it does not always remain unignited by operating upon it in this

Its ignition, however, is very much facilitated by scattering some finely powdered rosin amongst its fibres, as you will presently see, by sending a discharge of a similar quantity of electric fluid through it.

Now, iu order to convince you that the ignition of the tow and rosin is a general result of this mode of operating, I will repeat the experiment a few times, and you will then have ocular demonstration of the fact.

If, instead of rosio, I sprinkle the tow with oil of turpentine so as make it somewhat moist, you will see by a few experiments that the ignition is as easily

and as regularly accomplished as by the employment of the rosin. We occasionally employ other inflammable matter amongst the fibres of the tow, for purposes of this kind; and when tow is not at hand, other fibrous matter, such as cotton wool, is resorted to, but sheeps' wool is seldom, if ever, employed.

In all these experiments you will have observed, that a considerable report attended each discharge of the jar, which, as I have before shown you, can take place under no other circumstance than when the velocity of the electric fluid is very great; for if we abate the velocity, by passing the fluid through an inferior conductor, the wet string, for instance, scarcely an audible noise attends the discharge. But for fear of taking too much upon credit, I will vary the experiment in different ways, and I think the results in every case will serve as so many facts, in the direct process of demonstration.

In the first variation of the experiment I will again place a ball of tow, sprinkled with oil of turpentine, between the balls of the universal discharger; and in another part of the circuit I will place another ball of tow, sprinkled with powdered rosin, between two other insulated balls. Between the inside of the jar and the first portion of tow, I place in the circuit a piece of tinfoil, between a few leaves of writing paper; and on the other side of the latter ball of

tow I place some loose gunpowder. Now, by this arrangement, the electric fluid will have to traverse the whole of these bodies; first, through the paper and tinfoil; next through the tow and turpentine; then through the tow and rosin, and after leaving that combination of inflammables, it will traverse the loose gunpowder, and proceed to the outside of the jar. The results of the discharge of the large jar, from a high intensity, are easily predicted by those conversant in experiments of this kind; but to others there may appear to be some thing mysterious in them, Now we will discharge the jar. The result on the two balls of tow are probably such as you might be led to expect—both are set on fire; but what has become of the gunpowder? It also is an inflammable body, but it is not ignited, nor, indeed, is it left in its place. It is blown away, and scattered in every direction, from the axis of the electric path; not even a single grain is left where the fluid passed through the heap.

You will probably ask how I know the path of the discharge through the gunpowder, now that it is gone from the place ? This is very easily ascertained; for if you will examine the card on which the powder was placed, you will find it perforated by the electric fluid, and by calling to your recollection the position of the gunpowder on the card previous to the discharge, you will identify the perforation with the centre of the base of the heap. Consequently the electric fluid, which has so obviously pierced the card, must have traversed the gunpowder from the pointed wire above it, to the perforation of the card, But you

will observe also that this perforation is the centre of the blank space on the card left by the gunpowder. Hence we have, by this fact, a complete demonstration not only of the existence of the lateral force of the discharge, but also a demonstration of that force being exerted on every side alike.

Now call to your recollection that you have already seen that no card can be pierced by a discharge of this jar when a wet string forms a part of the circuit; and that I have shown you that, through such a circuit the velocity is much lessened. From a knowledge of these facts you are led to understand that the velocity, and consequently the mechanical action of this discharge, must have been great, otherwise the card could not have been perforated. Moreover, the scattering of the gunpowder is another manifestation of a great velocity and consequent momentum of the discharged electric Auid.

Now let us examine the paper and tin foil in the other part of the circuit. Both are perforated: another indication of the great electro-momentum attending the discharge of the jar through this compound circuit.

Let us now make a slight change in this experiment, by introducing a piece of wet thread as a portion of the circuit

. The jar shall be charged to the same intensity as before, but the result of the discharge will be very different. Neither the paper nor the tin foil will be perforated; neither of the balls of tow will be burnt, but you will see the gunpowder exploded. If, however, I were to enlarge

the lateral dimensions of the aqueous part of the circuit so as to increase the velocity of the fluid, and thus permit it to move in a more compact body, the paper and tin foil would suffer perforation, and the whole of the inflammables would take fire.

It is a remarkable fact that the gunpowder should not ignite under the same circumstances that accomplish the ignition of the other bodies; but time seems to be an essential element to insure success, and it is a matter of no consequence what are the means employed to give sufficient time for the electric fluid to be in contact with the gunpowder, for it will invariably ignite provided a sufficient period of time be procured, and the quantity of electric fluid transmitted be sufficient also.

Gunpowder has been ignited by a series of heavy sparks from a large prime conductor transmitted through a compact cartridge; but, in this case, the quantity of fluid was great, and the velocity lessened by the retarding power of the gunpowder itself, which being confined could not be blown away, Heavy discharges, with great velocities, from a battery of jars, have also been the means of igniting gunpowder; but in those cases the ignition of the powder was a secondary effect, arising from the wire which led the fluid into the cartridge being intensely heated by the discharge of the electric battery. Formerly it was a common practice to mix the gunpowder, intended to be exploded by electricity, with iron filings, which, becoming red hot by the discharge, set fire to the gunpowder as a matter of course. And we are not without those, at the present day, who conceal a thin platinum wire in the powder, for the purpose of accomplishing the explosion.

Another method of illustrating the fact that the ignition of loose gunpowder requires time for the electric fluid to be amongst its particles, and a consequent abatement of the velocity with which it moves through a circuit of good conductors, is that of first placing a portion in a circuit of that kind; transmit through it a discharge of a certain degree of intensity of the jar, and you will find the

pow der blown away as in the compound circuit of paper, tin foil, tow, and gunpowder, when all the rest of the circuit was metal. Having satisfied yourself on that point, next vary the arrangement, by placing a wet thread in the circuit. The discharge of the jar from the same degree of intensity, explodes the powder.

I have already shown you that, by an introduction of the moistened thread as a part of the circuit, the electro-momentum is sufficiently abated to be deprived of the power of communicating a shock to a person through which the fluid passes. Now, from that fact, and from the fact also of accomplishing the ignition of gunpowder when the electro-momentum is thus abated, there can be no reason why the gunpowder should not be ignited by the same discharge of the jar, in the circuit of which a person is placed without experiencing the shock.

Now, in order to give a striking illustration of this fact, I will place a battery of six miniature pieces of ordnance in one part of

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