of bismuth hardens it to such a degree that, notwithstanding repeated annealings, it cracks under the blow of a hammer.

The addition of aluminium to other metals is often attended with advantageous results, if the amount added be not too considerable. Ten per cent. of this metal mixed with copper imparts to the latter the brilliancy and colour of gold; and at the same time, without injury to its malleability, it imparts to it sufficient hardness to enable it to scratch the alloy of gold employed in our currency. Copper containing ten per cent. of aluminium is an alloy of a pale gold colour, possessing at once considerable malleability and great hardness, and capable of assuming a brilliancy equal to that of polished steel; it also gives silver a great degree of hardness, without in any way altering its other useful properties.

BORING.

THE art of boring is one of great value and of no little degree of antiquity, but until within a few years it had not received that degree of attention it practically merits.

The varied character of the English strata, the frequently limited area occupied by one series of rocks, the undulations and varying depths of beds economically valuable, and the proximity of others comparatively worthless, tend to render a knowledge of boring a matter of the highest interest and importance. Notwithstanding this, however, it is an art which has scarcely received any attention in this country, and we chiefly owe our information on the subject to the researches and experiments of continental engineers. This is the more surprising when we consider that the results of the development of the mineral resources of the country have, during the last few years, proved the presence of valuable and accessible beds of coal, clays, and marbles, in places where, but a short time previously, their existence was entirely unknown.

Boring is chiefly employed in searching for coal and ironstone; but, whether applied to the discovery of beds of coal, ironstone, marble, clays, salt, gypsum, limestone, slate, springs of medicinal waters, or water for domestic purposes, brine springs, or even the existence of combustible gases, it must be conceded that the development of an art which must increase our facilities for the attainment of such information is of great practical importance.

The chief improvements in boring appear to have been made during the last thirty years, and although the art has been known in China during many centuries, and used to an extent which, for depth of workings, has not been exceeded by the deepest continental borings, yet but one stereotyped system was invariably followed for all descriptions of rock.

The first and most simple method now employed is that by means of a tool similar in its action to the common carpenter's auger: this tool is termed a wimble. It has, however, the evident fault of being only applicable to soft or yielding ground; its use is therefore extremely limited. Where great depths have to be attained, or hard ground passed through, a percussion arrangement is made use of.

Under ordinary circumstances this consists of a chisel-edged tool, similar to the common borer of the miner, attached to a series of iron rods, which by means of male and female screws, are fitted into one another. These are lifted a certain height by a spring pole, to the end of which they are attached by a swivel joint. This arrangement may be worked by manual or other power, and is first raised and then allowed to fall against the bottom of the hole, whilst at each blow the whole set of rods are turned a certain portion of a revolution by means of a cross-head lever fitting tightly on the top rod. By a repetition of these blows and gradually turning the boring bit in the hole, so that it shall strike various radii on the surface of the bottom, a certain portion of rock is reduced to powder; this mixes with water, forming a kind of paste. When it has accumulated to such an extent as to impede the action of the cutting tool, the rods are removed, by separately unscrewing them, and a sludge bucket to remove the powdered material is introduced in its stead. This consists of a short cylinder of the size of the hole, with a valve in its bottom opening inwards, which being, lowered to the bottom of the hole, the valve opens and the sludge or pulverized rock enters the cylinder, which is then drawn up; the valve, of course, closing on the bucket being elevated. The rods are subsequently reintroduced, and a similar series of operations again carried on.

Among those who have improved the form of the cutting tools, we may mention Mr. Ryan, who, about the year 1790, invented a tool by which cores or solid portions of the strata of the size of the bore-hole might be extracted, as well as Mr. J. Good, who, in 1823, took out patents for various arrangements of this kind.

Since that period great advances have been made in this art, by the talent brought to bear upon it by Messrs. Kind, D'Eynhausen, Degousée and Fauvelle, who have been eminently successful, even where they have met with difficulties of such a nature as to entirely prevent the use of the common chisel-edged tool and iron rods.

To the use of continuous iron rods there are two great objections: first, their liability to break, from repeated percussions and vibrations through their entire length, which produce a molecular change in the iron similar to that which takes place in railway axles, and which has been termed the "Fatigue of metals ;" and secondly, this constant percussion and tremulous action of the rod lashes it against the side of the hole. When it is remembered that this action is repeated as often as 15,000 times in a day, and continued for many months without intermission, it will be readily understood that the softer portions of the strata through which the hole has passed will be liable to crumble and give way: this takes place in some instances to a considerable extent. Sometimes, also, portions

of the rock get jammed between the rods and the sides of the hole, and thus entirely prevent their extraction.

To obviate this, M. D'Eynhausen has invented a slide on the rods. This is inserted at a height of 5 or 6 lengths of rod above the tool, so that it confines the shock of the fall to that portion of the arrangement. The weight of the upper rods is also counterbalanced, and they thus only serve as a support to the lower ones. The upper rods are also, for the sake of lightness, often made of wood, jointed together by male and female screws.

M. Fauvelle has introduced improvements in this art of a remarkably novel and ingenious nature. They consist in boring with hollow rods of a size considerably less than that of the hole: down these tubes is forced a stream of water, and by this means the loss of time consequent upon taking out the rods and introducing the sludge bucket is altogether obviated; since the downward current in the tubes, striking the bottom of the hole, forces to the surface the particles of rock removed by the cutter. There is also a great advantage gained by always having a clean surface for the tool to act upon. When boring in ordinary strata, this current is forced down the tubes; but when boring through sand or gravel, the current is forced down the outside, whilst the debris ascends through the interior of the tubes. By this means stones of the size of 2 inches by 1 inch have been brought to the surface.

In point of saving of time some extraordinary results have been obtained by M. Fauvelle. A boring was made by this system at Perpignan, to a spring 186 yards from the surface, in July, 1846: the time occupied in reaching this distance was 140 hours of actual work, extending over a period of 23 days. A similar boring at the same place, carried on by a different system, occupied 11 months.

There are, however, objections to this plan which have prevented its more general adoption; the first is the porosity of some kinds of rock, which causes the absorption of more water than the tube is capable of supplying; another is the action of large quantities of water entering the hole from between certain beds of rock. The first would prevent the debris from being carried to the surface, from the fact of the non-existence of the means; whilst the second would so far interfere with the current as to render its action only partial. In deep borings this system appears to be very inefficient.

The system of the Chinese, which has been so long practised in that country, is again coming into use in Europe; the modus operandi of this system may be thus described. The cutting tool is suspended by a rope wound on a drum, this is turned so as alternately to lift the cutter and then allow it to fall, as in the case of ordinary percussion rods. The chisel for this purpose is made

heavy and its shank hollow, the arrangement being made to turn by the simple torsion of the rope. By this means holes of considerable size have been bored, as, for instance, some near Manchester of 3 or 4 feet in diameter; it has also been used to bore for the purpose of colliery ventilation. Its merits are-cheapness of execution and the short time required to effect the object, since there are no rods to be unscrewed, but the tool is simply wound up by the rope and drum. Its objections are-the difficulty of keeping the hole perfectly vertical or straight, both of which are necessary should it be required to introduce tubing; there is also the difficulty in boring through hard and highly inclined strata by this means.

The Abbé Imbert relates that he had seen holes, in China, bored by this means from 500 to 600 yards deep for the sum of from £400 to £500.

A modification of the Chinese system has been introduced by the Société Freminville, which chiefly consists in tubing the entire length of the hole. The tubes employed for this purpose are gradually put down as the boring progresses. In order to allow this to take place they are kept loose in the hole by turning, and a chisel works in grooves in the lower end of the tube; after having bored a certain depth by percussion from this chisel, a forked tool with saws at the extremities, which are forced outwards by a ring, enlarges the hole to the requisite size, and allows the tube again to descend. Good results have been obtained by this method, and it is one of those to which the Société has devoted a considerable amount of attention.

The last system which we shall notice is that of M. Kind, who has introduced a number of most valuable improvements, and brought the art to greater perfection than any other engineer.

Among M. Kind's improvements we may notice three :-First, the use of light wooden rods; secondly, the employment of a "free fall" percussion tool; and thirdly, the method of obtaining a core or piece of rock of the size of the bore-hole, and of considerable length, which enables the operator to form a correct idea of the character and dip of the strata.

The advantage of the use of wood over iron rods is obviously their light weight, more especially when we consider that the boreholes are usually filled with water; the wood itself soon gets saturated with moisture, and the iron screws and ferrules at the end of each render the whole mass of a greater specific gravity than the water in which it is immersed, only to such an extent as to allow of their falling freely through the liquid by which they are surrounded.

The free fall tool consists of an ingenious arrangement by