CHAPTER XV.

THE EARTH CONNECTION.

To dwell too largely upon the importance of leading all lightning conductors down into moist earth, or, as technically called, ‘good earth,’ would be scarcely possible. It would perhaps not be too strong an expression to say that the part of the conductor above ground is a mere appendage to that under ground, the essential function of the whole apparatus--that of dispersing the electric force harmlessly--being accomplished by the subterranean portion. The clear understanding of Benjamin Franklin perceived this at the outset; but after him it seemed as if forgotten for a long time, and the result showed itself in numerous disasters that occurred to buildings protected with conductors, which brought the latter into disrepute with many persons. While, no doubt, in many instances the cause of these disasters was in the bad application of the conductors themselves, their defective character, or their feebleness, still in the great majority the underground connection may be taken to have been in fault. It may be laid down as an absolute certainty that a really good conductor--say, a copper rope from five-eighths to three-quarters of an inch in thickness--cannot possibly fail to carry off the electric force if the lower part reaches moist earth or water. Probably, in nine cases out of ten, whenever a building provided with a conductor is struck by lightning, it is for want of ‘good earth.’

Franklin’s own ideas were very clear on the subject. He laid them down at various times, more particularly when residing in England, during the years from 1764 to 1775, as colonial agent for Pennsylvania. During the latter part of this period he took an active interest in the proceedings of the Royal Society; and this learned body being requested by the Government to give advice regarding the best protection against lightning that could be provided for the great powder magazines at Purfleet, he was nominated into a committee with three other members, William Watson, H. Cavendish, and J. Robertson. The committee drew up a report, dated August 21, 1772, signed by all the members, but known to be written by Franklin alone. Dwelling strongly on the importance of the underground connection, Franklin says in this report: ‘In common cases it has been judged sufficient if the lower parts of the conductor were sunk three or four feet into the ground, till it came to moist earth; but this being a case of great consequence, we are of opinion that greater precaution should be taken. Therefore we would advise that at each end of each magazine a well should be dug, in or through the chalk, so deep as to have in it at least four feet of standing water. From the bottom of this water should rise a piece of leaden pipe to, or near, the surface of the ground, where it should be joined to the end of an upright bar.’ Franklin then goes on to recommend the usefulness of having even more wells than the two, so as to avoid any possibility of failure in protecting the powder magazines. ‘We also advise,’ he says in his report, ‘in consideration of the great length of the buildings, that two wells of the same depth with the others should be dug within twelve feet of the doors of the two outside magazines--that is to say, one of them on the north side of the north building, and the other on the south side of the south building, from the bottom of which wells similar conductors should be carried up.’ It is not on record whether these recommendations were adopted by the Government, but it seems likely that this was the case, as the fear of explosion of powder magazines through a stroke of lightning was very great at the time. Not long before, a magazine had been so destroyed at Brescia, in Italy, with the appalling result of a considerable part of the city being laid in ruins, burying many hundreds of persons. The destruction of the Brescia powder magazine, like all similar events, had, it is scarcely necessary to say, its due effect in spreading a desire for lightning conductors, fear doing what was not effected by foresight.

Whether or not the English Government made the wells recommended by Franklin for the Purfleet powder magazine, it is certain that the sound advice given was not largely followed. On the contrary, there grew a generally prevailing laxity in regard to the indispensableness of a good underground connection, which led to numerous accidents. They were seldom, however, ascribed to the right cause, others being sought instead--such as particular forms of conductors and the insufficient length of those phantoms called ‘reception-rods,’ which, as many thought, could never be made high enough, in order to ‘draw the electric fluid’ from the clouds. Height was sought where nothing but depth was required, and the same unsightly rods, towering high above buildings, would have very effectually carried off the electric forces if brought from the top to the bottom of the conductor, being taken out of the air and stuck into the earth. Still, there were not wanting philosophical minds impressed with the truth that no lightning conductor can discharge its functions unless rooted in moisture, and who not only knew it, but did their best to spread this knowledge in all directions. One of these philosophers, a singular character in his way, was a German clergyman, the Rev. Dr. Hemmer, who lived at Mannheim, on the Rhine, at the end of the last century. Taking the deepest interest in Franklin’s great discovery, he made many experiments with lightning conductors, which brought him to the conviction that the electric force, in its chief tendency, seeks the mass of water on the globe, and that where this is not on the surface, it must be guided to it to become harmless. Consequently, he recommended to sink the conductor invariably deep into the ground, so as to reach water, and to subordinate everything else to this prime necessity. To make the use of lightning conductors as general as possible, Dr. Hemmer not only wrote a number of little books, which he liberally distributed, but travelled about through many parts of Germany, instigating the authorities to place conductors on all public buildings, and the people to set them up over their own houses. Holding that the earth connection was everything, he advocated simply to dig a hole in the ground till water or very moist earth was reached, and to stick a small iron bar, wrapped in lead to prevent rust, into it, running up the roof. The bar any village blacksmith could forge, and the hole any man or boy could dig, thus making the absolute cost of the conductor under this arrangement very trifling. Dr. Hemmer was right, no doubt, in his main argument, and most successful in spreading the knowledge of lightning conductors, while he was able to boast that not one of all the number he had set up had ever failed. However, he lived in an age when as yet water and gas pipes were unknown, and iron, or any other metal, scarcely entered into the construction of buildings. Given a leaden roof and a network of metal tubes, and Dr. Hemmer’s small iron rod could scarcely be expected to do its work of protection.

Together with Dr. Hemmer in Germany, Professor Landriani, of Milan, drew attention to the paramount importance of a perfect earth connection. He made it his special business to investigate cases in which buildings with lightning conductors had been struck, and was able to show in nearly every instance that it had been for want of ‘good earth.’ A very striking case, which ought to have brought conviction of the truth to all investigators of the subject, occurred in Genoa in 1779. The church of St. Mary in this city, standing in a very elevated position, had been frequently struck by lightning, sometimes as often as twice in one year, and it was noticed that the electric force always followed precisely the same path, running along a certain portion of masonry, partly secured by iron hoops, and finally demolishing a wall at the bottom to get into the earth. At last, in November 1778, a conductor, made of the most approved design, was placed over the church, but, to the great surprise of the scientific men who had superintended the work, the lightning fell once more upon the building in the month of July of the following year, again following the old path it had constantly taken before, and causing absolutely the same damage as previously, even to the knocking out of certain portions of the wall nearest the ground. Naturally, the event caused widespread interest, leading to the closest examination of the church of St. Mary by several experts, among them Professor Landriani. He had no great trouble in discovering both the causes of the path of the lightning having always been the same when falling upon the church, and of the edifice having been struck again in the same manner when provided with a lightning conductor. Being a somewhat peculiar structure, consisting in part of hewn stones held together with iron cramps, there was a large quantity of metal both in and outside; and it was found that the path of the lightning had always been precisely in the direction where the metal offered the greatest continuity, leaping over the short intervals that existed by destroying the stone, and finally getting into the ground to a place where there was always a collection of water by knocking down a wall. If this accounted satisfactorily for the former accidents, that which took place when a conductor had been placed was not much more difficult of explanation. Professor Landriani found that though the conductor itself was very good, it was useless simply by having its roots in hard rock instead of moist ground. On the one side of St. Mary’s Church there was a rill of water rippling down from the hills, and forming a small pool near the church, while on the other was the hard rock. It was into a crevice of the latter that the conductor had been laid, thus leaving the electric force to seek its old path into the water along the iron bars, which, although disjointed, formed a far better road to earth than the planned road. It was a convincing proof of the supreme necessity of a good earth connection. Still, a long time yet was to elapse before conviction became general.

Probably, the matter was more studied by Italian scientific men than any others, the study of electricity having always been a favourite pursuit in that country; yet there, too, the matter was not understood till quite recently. This is proved by a letter of the celebrated astronomer and meteorologist, Father Secchi, addressed to the French scientific journal ‘Les Mondes,’ in October 1872, in which he tells the story of an accident that befel a building protected by lightning conductors set up under his own direction, the earth connection being made after rules laid down by Professor Matteucci, considered the leading authority on the subject. The letter of Father Secchi, though of some length, is given here entirely, both on account of the great fame of the writer, but recently deceased, and because it throws a flood of light on some of the most important points connected with the art of designing and applying lightning conductors.

‘Eight years ago,’ says Father Secchi, writing, as just mentioned, in 1872, ‘some lightning conductors had been erected under my direction on the cathedral and on the Bishop’s palace of Alatri, situated at the summit of the Acropolis of that town, which, by its elevated and solitary position, was exposed to frequent ravages from storms. It was not long ago that a flash of lightning demolished a great part of the belfry, and damaged the organ of the church. In the erection of this lightning conductor there arose a great difficulty proceeding from the nature of the soil, which at the depth of some centimetres turns out to be entirely of solid calcareous rock.

‘In order to remedy this defect, that part of the conductor which enters the ground has been made very long, more than 4 metres [13 feet], and has been provided with a great many couples of points, 5 centimetres [2 inches] broad, 5 millimetres [⅛ inch] thick, indentated on the edges, with the addition of a thick copper wire twisted among the same points, to help to multiply the points of contact between the rod and the carbon. The foot of the lightning conductor is entirely of copper. The rod is also of copper up to a metre [3¼ feet] above the ground; and there is joined to it the iron conductor, in the ordinary receptacle made in the heart of the wall, to preserve it from disturbances of the inferior parts. The ditch into which the foot of the lightning conductor was sunk is 5 metres [·16 feet] long, and half-a-metre [1⅝ feet] wide, and it was dug into the ground as far as to touch the roots of some neighbouring trees, from which point upwards a layer of cinders was placed, covering the greater part of the ditch. Thus the surface of contact between the metal and the carbon, and of the latter with the soil, was such that one would have supposed it to be more than sufficient, while the presence of trees, although they were not very large, made it highly probable that the ground did always contain sufficient moisture. Moreover, as the edifice had two culminating points--namely, the belfry and the raised back portion of the choir--two rods were placed on them, each having an independent connection with the earth, so that, in the case of a discharge on one of the points, the electric force might find two ways in its course towards the earth.

‘These arrangements produced, on the whole, a good result, since, although the edifice was struck at least four times after conductors had been placed on it, it suffered no damage of any kind. Nevertheless a very curious accident, highly interesting as a scientific study, happened on October 2. Early on the morning of this day several flashes of lightning fell down from the clouds during a terrific storm, which lasted over two hours. The belfry was struck at first by weak discharges twice; but the third flash was so appalling in its strength as to terrify the whole town below. The injuries it caused were not great, still they seemed to me to be extremely noteworthy. But before I describe them I must give some necessary details as to place and position of the lightning conductor.

‘It so happened that four years after the erection of the conductor a line of pipes was laid down to carry water to the towns of Alatri and Ferentino, passing at a short distance from the belfry of the cathedral. The lightning conductor was not placed in communication with the pipes, because it seemed established, from previous experiments and observations, that it was needless to do so, the ground containing apparently sufficient moisture, the head of the waterworks being close, and there existing also a running fountain. I was not asked at the time whether it was necessary to establish this communication, but, had the question been put to me, I should probably have answered it in the negative, considering, from what I then knew, the work as superfluous. That I was in error then as to the necessities of a perfect underground connection is shown by what happened during the great storm in the early morning of October 2. The heavy flash of lightning before referred to did not go its appointed path underground, but passed off into the waterworks, with the following results:—

‘1. It made in the earth a perfectly rectilinear excavation, which, from the lower part of the conductor, went to the tube of the waterworks running to Ferentino, and in traversing the wall destroyed the angle of that structure. The earth of the ditch thus dug was disposed regularly to right and left with great symmetry. The length of the ditch was about 10 metres, the depth about 70 centimetres [28 inches].

‘2. The lightning struck the water-pipe of Ferentino, broke it completely, throwing the pieces to a distance of about 80 centimetres [32 inches]. The lead which soldered the joint of the broken tube with the tube beyond was found melted. In consequence of this rupture the water ceased flowing to Ferentino, and poured into the waterworks.

‘3. Another part of the discharge spread itself by the pipe which goes to Alatri, and traversing the reservoir threw to a great distance some wooden plugs which stopped up the discharging tubes, the plugs being forcibly hammered in. It arrived at the town in a tank, where it damaged and twisted in a strange manner a leaden slab which was in the tank, made some other little injuries, and finally left the trace of its passage at the spouts of the public fountain.

‘4. The point of the lightning conductor was examined, and it was found very blunt; it was found impossible to unscrew it, and it could not be removed without breaking the screw. It was found broken to a length of more than 3 centimetres [1¼ inch], and the section of fusion was nearly flat, as though it had been cut. The gold of the gilding had nearly all disappeared. In the church, and in the edifice which is attached to it, no injury was detected. These facts appear to me important both as regards practice and theory: in respect to theory, because they give an idea of the quantity and of the immense force of the discharge. The melting of the point down to a section 1 centimetre [½ inch] in diameter proves that it would have been melted down much further if it had been slighter. It is not prudent, then, to use very slender points; it is best that they should thicken quickly.

‘The excavation of the ditch at the foot of the lightning conductor could not be the direct effect of electricity, but would be the result of the sudden evaporation of the moisture of the ground, generating steam, and forming, as it were, a mine.

‘The breaking of the tube is most singular. It seems to me that it can with difficulty be attributed to the mechanical shock of the electricity itself. As the lead which united the broken tube to the one beyond was found melted, it is evident that, in spite of the water which flowed in this tube, it was raised to an enormous temperature in the place where it was struck, and probably it was the instantaneous evaporation of the water inside which caused the breaking of the tube.

‘But the most singular fact, in a certain respect, is what was observed in the tube which descends to Alatri--that is to say, the alteration in form of the leaden slab. The little interruption which necessarily exists in this tank between the conducting-pipe and the metallic receptacle evidently gave occasion for a discharge by a flash, and, in consequence, for an explosion of steam. But we see at the same time by that that the distance traversed in the tube from the building to the slab, a distance of more than 200 metres [650 feet], in which the pipe is buried underground, did not suffice for the charge to lose itself in the ground, although during the passage it had to cross the reservoir, and might there have distributed itself. Our surprise is still greater when we reflect that it was only part of the discharge, since the greater portion had to flow by the water-pipe of Ferentino, which was the first struck in a direct manner, and that these pipes are joined together with lead. The quantity of electricity must have been enormous, in order to be able to have so much force and to run another 300 metres [975 feet] to reach the public fountain, and leave its traces there. A circumstance which deserves attention is, that this storm took place after a long and constant drought; and consequently the earth was less moist, and could offer little facility for dispersion.

‘These cases are not so rare among us as one might suppose. Not very long ago, at Lavinia, a flash of lightning destroyed a great part of the belfry, passed to the bell, broke and melted it in its passage in such a manner that the metal had run away like wax. I do not believe this breakage of the bell to have been a mechanical effect of the lightning in a rigorous sense, for the bell could have been broken by the instantaneous expansion produced by the heat at the point of the passage, an expansion which had had no time to disperse, as a glass vase breaks when touched with a red-hot iron.

‘Let these facts come about how they may, they enable us to see that it is necessary to devote great attention in the erection of lightning conductors, that we must allow them a large surface for discharge, _and that there can never be too much of it_. The surface of the foot of our lightning conductor was certainly superior to what has been judged sufficient by Matteucci for the discharges of telegraphic conductors, and yet it has not sufficed. Further, it is a confirmation of the necessity of making the neighbouring metallic masses communicate, and especially with water and gas-pipes.’

From out of the almost endless number of cases in which lightning conductors failed for want of a good earth connection, another one or two may be given, illustrated as having happened quite recently in England, and as such showing, in a very striking manner, in what a neglected state the knowledge of the subject still is at this moment. A thunderstorm passed over the town of Clevedon, Somersetshire, in the afternoon of March 15, 1876, and a flash of lightning fell upon the steeple of Christchurch, provided, as was generally thought, with a most efficient conductor of recent construction, made of good copper rope. What happened is graphically and minutely told in a letter addressed to the ‘Journal of the Society of Telegraph Engineers,’ by Mr. Eustace Buttor, of Lewesfell, near Clevedon. ‘There was but a single flash,’ Mr. Buttor relates, ‘which appeared to many observers to travel horizontally through the air. However, the lightning passed down the lightning conductor of Christchurch. The flag-staff, about 100 feet high, and the four pinnacles, about 90 feet high, have each a conductor, the flag-staff having the usual conical point, the pinnacles having the copper rope attached to their vanes. The five copper ropes unite inside the tower in the neighbourhood of the clock. Lower down the conductor passes through a slanting hole to the outside, and for the lowest 12 feet is encased in a pipe. On reaching the ground it passes into a dry freestone channel for about a dozen feet, and then dips down into the drain which carries rain-water from the roof. As no rain preceded or accompanied the flash, it may be presumed that _the drain was dry_.

‘The protector is copper throughout, and, with the exception of the termination, seems to have been carefully and efficiently placed. The diameter I estimate to be half-inch, or it may be a trifle more. Just at the point where it leaves the pipe and enters the ground, the electric charge left it, dashed through three feet or more of solid wall supporting the tower, in order to reach the gas-meter inside, then it passed safely along the gas-pipe. The cavity made was considerable, but very irregular. I was unable to ascertain when the workmen were engaged in repairs, and therefore cannot give their estimate of the weight of stone displaced, but it must have been many hundredweights, though only a few pounds were actually thrown out on to the path, or inside into the vault. A large quantity of stone was pulverised, and the whole gave one the idea of the explosion of a charge of gunpowder under great compression. In a house about 100 yards from the church, the inmates felt the shock intensely, but did not know that the house had been touched. Some hours after, however, on going to turn on the gas, a hissing noise was heard, and a hole was found in the composition gas-pipe, about five-eighth inch diameter, just where the pipe passed within an inch of a water-pipe. The lightning must have come along the main from the church gas-pipe to this house, and then passed to the water-pipe as the readiest way to moist earth. The whole soil in the neighbourhood is mountain limestone, very dry. There is not the slightest evidence of displaced plaster, or any other sign of the passage of an electrical discharge through the house.’ There need be little comment on the facts stated in this letter, notable though they are. It is the old delusion that a lightning conductor need be brought down underground only, and that then all is right. In this case, those who protected Christchurch, Clevedon, thought it quite sufficient to bring the conductor down into a drain-pipe carrying rain-water from the roof, without reflecting for a moment that an earthenware drain-pipe would insulate the conductor from ‘earth.’ A similar instance came under the writer’s notice about a year ago. One of the pinnacles of Cromer Church, in Norfolk, was struck by lightning, although fitted with a conductor on one of the pinnacles. On examination it was discovered that the earth terminal had been inserted into an earthenware drain.

It is not very easy to give exact prescriptions as to the best manner in which the underground connection should be effected. The means vary entirely with the circumstances, and the matter should in all cases be intrusted to an expert. Simple as is the whole theory of lightning protection, consisting in nothing else but laying a good metallic path from the top of a building down into moist earth, as an unfailing path for the electric force, the practical execution of it is not the less often very complicated. It is especially so as regards the most important of points, that of the underground connection. Of course, wherever there is running water at hand, a river, or even a tiny stream that never dries, the matter is easy enough, but as in the great majority of buildings to be protected such water does not exist, the solution of the question becomes more difficult, and frequently one of the greatest perplexity. It tends even to be more and more so in consequence of the progress of sanitary arrangements under which towns and villages are ‘drained’ until the soil has been made as dry as a rock. Immense as the benefit is to public health, it is, like all benefits, attended by certain drawbacks. One of these certainly is a greater danger from lightning. It is often proposed by builders to use the drain-pipes themselves in making ‘good earth’ for lightning conductors, but the fallacy of this recommendation need scarcely be exposed, seeing that these conduits are generally made of earthenware, as happened when Christchurch, Clevedon, was struck by lightning.

While broad rules cannot be laid down, still it may be affirmed that a good earth connection, sufficient to carry off the heaven’s electric discharges, may always be obtained by either of two means. The first, and in all cases most preferable, is to lay the conductor deep enough into the ground to reach permanent moisture. When this exists in a considerable mass, the single conducting rope, touching it, will be quite sufficient; but when the quantity is deficient, or doubtful, it will certainly be advisable to spread out the rope, so as to run in various directions, similar to the root of a tree, likewise in search of moisture. There are various modes of accomplishing this, shown in figs. 46 and 47.

A variety of methods have been proposed for the dispersion of the electric force underground where the soil contains little or no moisture, except at great depths, to be reached only by a vast amount of labour and expenditure. In France, the system most generally adopted in these cases is to place at the bottom of the underground connection an apparatus, made either of iron or copper, shaped somewhat in the form of a harrow, and to embed it thickly in charcoal. Fig. 48 will illustrate this system of earth connection.

The apparatus is as simple as it may be useful, and the more so, of course, the thicker the mass of charcoal in which it is embedded. But it may be doubted whether it is sufficient to make ‘good earth’ under all circumstances. Perhaps it will do so in ninety-nine cases and fail in the hundredth. The amount of electric force discharged in ordinary thunderstorms does not seem to vary much, and, according to all observations, such an artificial connection as this of the charcoal bed is sufficient to disperse it safely beneath the surface. But now and then there come storms of extraordinary violence, or, in other words, extraordinary accumulations of atmosphere electricity, which demand precautions such as are not fulfilled by the subterranean harrow, however thickly embedded in charcoal, or, as oftener done, in gas coke or cinders. It is certain that there have been cases in which buildings with otherwise excellent conductors, but provided with such an artificial earth connection, have been damaged by lightning. However, it may be stated, as the net result of all observations and known facts upon the subject, that small private houses can be well protected by this means against lightning, but that the system cannot be recommended as absolutely safe for large edifices and public buildings.

To protect any structure of great extent, it is absolutely necessary to bring the conductor, or conductors, deep enough into the earth to reach water. It is all the more indispensable with modern buildings, as they contain large masses of metal, not only in gas and water-pipes, but often in staircases and iron columns, towards which the electric force has the strongest tendency to direct itself unless drawn to the earth by an immediate and unfailing connection with the great sheet of water below its surface. It is considered by German electricians that there is no necessity, if a large edifice has a number of conductors, to let each have a separate earth connection; it is quite sufficient to bring them all into one, provided only that this is absolutely perfect at all seasons and under all circumstances. Fig. 49 will show how this can be done.

It will be seen that for the protection of this edifice there are six conductors, with four elevated points marked A, B, C and _c_. Two of these points, A and C, expand from the roof to the ground into double conductors, so as to protect the sides of the building against possible lateral discharges of lightning, and all the six conductors meet a little below the surface in the earth connection prepared for them. To form this one connection, either by digging or boring, may sometimes be costly, but whether the expenses be more or less, the protection against lightning thus effected will be so absolute as to be invaluable.

In a similar manner as the large edifice, with its many gables, a church may be fitted with lightning conductors. Fig. 50 scarcely needs much explanation.

There is one thing, however, regarding churches, that must be well borne in mind in establishing their protection against lightning. Besides containing great masses of metal, in bells, organs, and other contents, they are frequently placed in high situations, exposed to the most violent discharges of the electric force. It often happens also that they stand on rocky ground, with the subterranean waters far below the surface. To ensure absolute protection under these circumstances, it is indispensable to connect the conductors with water, wherever it is to be found, by a solid channel, into which the copper rods may run, if possibly some distance below the surface of the earth. The form such a channel may take is indicated on the engraving. It will be seen that the protection against lightning indicated here is not only for the church, but the adjoining parsonage, the conductors spreading over both, with points on the most prominent and exposed places. It would be possible to carry out this principle in ensuring the protection of a whole block of private buildings. German electricians think that one channel or well, sufficiently broad, leading from the surface of the earth to layers always moist, or to perennial springs, would suffice to carry the electric force discharged upon a hundred conductors, and all the easier as it would be impossible that many would be struck at one and the same time by lightning. Perhaps some such arrangements will be made in the future, when both houses and towns are built upon a more systematic plan than is followed at the present time.

If, as a rule, one channel of underground connection is amply sufficient for the protection of even the largest buildings, there may be cases in which it is indispensable to spread the conductors into several directions. It may be laid down, broadly, that when there is water to be reached, the one channel is sufficient, but that when this is not possible, or expedient, more lines of underground connection must be formed. Fig. 51 may serve to illustrate a case of the latter kind. It shows a powder-magazine, partly above and partly underground, standing on dry soil, with trees in the neighbourhood, likely to add to the danger of atmospheric discharges of electricity, and with no stream, or permanent moisture, into which to guide them. Nothing remains, under these circumstances, to ensure safety, but to multiply the lines of underground connection to the utmost extent. To add to the facility of the dispersion of the electric force, the main channels may be filled with charcoal, broken coke, or cinders, and if large quantities of these substances can be placed in one or two pits, it is possible to make thus an artificial connection as nearly as can be responding to ‘good earth.’ Still, it must never be forgotten that, absolutely, ‘good earth’ in reference to lightning conductors means moisture, or water.

If permanent moisture cannot be obtained and iron water-mains are within reach, it is desirable to connect the ground terminal with them by means of good solder, as from the large mass of metal they generally form very good ‘earths.’

In giving directions, or rather suggestions, about the design and application of conductors, and, what is most important in regard to them, their connection with the subterranean mass of waters, the idea that persons may construct their own conductors is left aside altogether as absurd. It is a good old proverb which says that a man who is his own lawyer is certain to lose his cause; another has it that a man who is his own doctor is sure to succumb to his illness. With regard to the setting-up of lightning conductors, it is precisely the same. Simple enough as is the theory of ‘drawing lightning’ from the clouds, the practical execution of it is, as mentioned more than once, not a little complicated. The formation of the underground connection, in particular, is a matter requiring very great experience, and very frequently one of the utmost difficulty. Vast sums of money are often thrown away needlessly in making a connection which in the end proves useless, while, on the other hand, a trifling addition to the expenditure in setting-up a conductor would procure its efficiency, not attained simply from want of ‘good earth.’ A recent writer on lightning conductors whimsically, yet with much truth, expresses it by remarking that ‘people spend money upon gilded points on the top of the house, while they ought rather to sink it in water at the bottom.’ Undoubtedly, the efficiency of conductors lies, even more than at the top, on ‘the bottom.’ The earth connection may be called ‘the alpha and omega’ of lightning protection.