Part 4
It is estimated that at least 45 persons are killed annually by lightning in this country. The average number of deaths by lightning has been 22 in England, 9 in Switzerland, 3 in Belgium, and 75 in France. In France alone, during a period of thirty years, over 10,000 persons were smitten, of which 2,252 were instantly killed. Eighty were wounded and 9 killed during one thunderstorm at Châteauneuf les Montiers in 1861, and within one week, when the air was highly charged with electricity, thirty-three fearful flashes of lightning were observed, each bringing death to some victims.
During the sixteen years between 1799 and 1816, 156 vessels of the British navy were struck by lightning; 73 men were killed and 138 injured, and the loss of materials amounted to over a million dollars; but since the system of metallic conductors, adapted for vessels, devised by Sir W. Snow Harris, has been applied to the vessels in that navy, the losses and damages by lightning have almost entirely ceased, although the number of vessels has been greatly increased.
In Fuller's Church History it is stated that "scarcely a great abbey in England exists which once, at least, was not burned down by lightning from heaven."
On the night of April, 1718, twenty-four steeples were struck along the coast of Brittany; and on the 11th of January, 1815, twelve steeples suffered a similar fate in the Rhenish provinces.
On the 27th of July, 1759, lightning burnt all the woodwork of the great cathedral at Strasbourg; and on the 14th of August, 1833, it was struck three times within a quarter of an hour, and so much damaged that the repairs cost about $6,000,000. In 1835 lightning conductors were placed upon the building and steeple, and since then it has not been damaged whatever by lightning, although discharges have on several occasions occurred in line with the top of the steeple, which is 437 feet above the ground.
On the 18th of August, 1769, the Tower of St. Nazaire, at Brescia, was struck, and the subterranean powder magazine, containing 2,076,000 lbs. of powder, belonging to the Republic of Venice, was exploded. One sixth of the whole town was laid in ruins and the rest very much injured, and about 3,000 persons killed.
On the 26th of June, 1807, the powder magazine of Luxembourg, containing 28,000 lbs., was struck, and besides about 30 persons killed and 200 injured, the town was ruined.
Explosions and large fires, involving a great loss, have become rather frequent in this country, owing to the iron tanks used for the storage of petroleum being struck by lightning. From March to August, in 1876, over 10,000,000 gallons, and on April 19, 1877, over 2,000,000 gallons of oil, and the village of Troutman, were destroyed in the oil regions of Pennsylvania.
Some of the thunderstorms which have prevailed in this country have been very terrific and destructive. During August 14th, 15th, and 16th, 1872, portions of New York State and the New England States were visited by some of the most terrific thunderstorms ever experienced, during which over 200 dwellings were struck and damaged, about 10 persons were instantly killed, and 160 stunned. Quite a number of barns, with their contents, hay and cattle, were also struck, fired, and consumed. Cars, while running on some of the railroads, were surrounded by a vivid electric light, but no passengers were injured, although they were greatly alarmed. Telegraph wires were melted by the half mile, telegraph instruments broken, and poles shattered in all directions. One of these storms occurred at midnight, at Arlington, Mass., August 14th, in which brilliant streams of electricity darted across the sky in every direction, and the thunder which followed was constant for a period of thirteen minutes, without the intermission of an instant of silence. Three hundred and thirty-one discharges were counted in seven minutes by an observer, and each discharge was followed by loud and sometimes rattling reports, whose reverberations rolled through the heavens in an endless procession of majestic and terrific sounds. During this scene, the moon, which was about half an hour above the western horizon, was visible, but so magnified, through the haze and vapor, as to appear like a brilliant flame suspended in the sky. For a period of twenty minutes the scene was one of grandeur and sublimity rarely witnessed.
In the States of Illinois and Iowa, and the prairie country west of the Mississippi river, thunderstorms are generally more terrific, and more lives have been lost there from the effects of lightning than in any other section of this country. Owing to the said country being level and devoid of trees, the equilibrium between the electricity of the atmosphere and that of the earth is principally restored by disruptive discharges.--_Spang's "Treatise on Lightning Protection"_
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A tooth of a mastodon has been dug up near the Ashley river in South Carolina. It is 11½ inches long, 6 inches in diameter, and weighs more than 5 lbs.
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THE SEA SERPENT SIGHTED FROM A ROYAL YACHT.
The Osborne, paddle royal yacht, Commander Hugh L. Pearson, which arrived at Portsmouth from the Mediterranean on Monday, June 11, has forwarded an official report to the Admiralty, through the Commander-in-Chief (Admiral Sir George Elliot, K.C.B.), respecting a sea monster which she encountered during her homeward voyage.
At about 5 o'clock in the afternoon of June 2, the sea being exceptionally calm, while the yacht was proceeding round the north coast of Sicily toward Cape Vito, the officer on the watch observed a long ridge of fins, each about 6 feet long, moving slowly along. He called for a telescope, and was at once joined by other officers. The Osborne was steaming westward at ten and a half knots an hour, and having a long passage before her, could not stay to make minute observations. The fins were progressing in a eastwardly direction, and as the vessel more nearly approached them, they were replaced by the foremost part of a gigantic monster. Its skin was, so far as it could be seen, altogether devoid of scales, appearing rather to resemble in sleekness that of a seal.
The head was bullet-shaped, with an elongated termination, being somewhat similar in form to that of a seal, and was about six feet in diameter. Its features were only seen by one officer, who described them as like those of an alligator. The neck was comparatively narrow, but so much of the body as could be seen, developed in form like that of a gigantic turtle, and from each side extended two fins, about fifteen feet in length, by which the monster paddled itself along after the fashion of a turtle.
The appearance of the monster is accounted for by a submarine volcano, which occurred north of Galita, in the Gulf of Tunis, about the middle of May, and was reported at the time by a steamer which was struck by a detached fragment of submarine rock. The disturbance below water, it is thought probable, may have driven up the monster from its "native element," as the site of the eruption is only one hundred miles from where it was reported to have been seen--_Portsmouth (Eng.) Times._
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SUNSTROKE.
The sudden accession of heat has already produced one fatal, and more than one severe, case of sunstroke in the metropolis. Probably the affection so designated is not the malady to which the term _coup de soleil_ can be properly applied. The condition brought about is an exaggerated form of the disturbance occasioned by entering too suddenly the "hot" room of a Turkish bath. The skin does not immediately perform its function as an evaporating and therefore cooling surface, and an acute febrile state of the organism is established, with a disturbed balance of circulation, and more or less cerebral irritation as a prominent feature of the complaint. Death may suddenly occur at the outset of the complaint, as it has happened in a Turkish bath, where the subject labors under some predisposition to apoplexy, or has a weak or diseased heart. It should suffice to point out the danger and to explain, by way of warning, that although the degrees of heat registered by the thermometer, or the power of the sun's rays, do not seem to suggest especial caution, all sudden changes from a low to a high temperature are attended with danger to weak organisms. The avoidance of undue exercise--for example, persistent trotting or cantering up and down the Row--is an obvious precaution on days marked by a relatively, if not absolutely, high temperature. We direct attention to this matter because it is obvious the peculiar peril of overheating the body by exertion on the first burst of fine weather is not generally realized. It is forgotten that the increased temperature must be measured by the elevation which has recently taken place, not the number of degrees of heat at present recorded. The registered temperature may be more or less than that which occurred a year ago; but its immediate effects on the organism will be determined by the conditions which have preceded it and the violence of the change.--_Lancet_.
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DEAD HORSES STANDING ERECT.
The Danville _Advertiser_ of the 7th inst. says: Mr. Smith was in town on Saturday with his hired man, and the two tell a singular story about a lightning stroke. Mr. Smith was on a grain drill in a field, and his hired man was about 12 rods from him, dragging. Suddenly Smith heard the noise of thunder, and became unconscious. The man also heard the noise, but neither of them saw any flash of lightning. The man went to Smith, and in about twenty minutes he was restored to consciousness. Then attention was given to the horses. One of them was standing erect, with one foot lifted a little way from the earth, and the other was kneeling with his nose in the earth, and both were stone dead, and retained their positions until they were pushed over. The supposition is that in this case the electricity went from the earth to the sky.
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The Berlin correspondent of the London _Times_ states that General Berdan, of the United States, has invented an instrument which will greatly improve the art of killing. He calls his invention a "range-finder." It consists of a telescope and other instruments, all of which can be carried on a dogcart, and which enable the engineers to measure with perfect accuracy up to 2,000 metres, or 1,500 yards. The time needed to ascertain distances, is only two minutes, and the General believes that his invention will double the accuracy of artillery fire, and quadruple that of infantry.
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SETTING LOCOMOTIVE SLIDE VALVES.
BY JOSHUA ROSE.
E. G. asks: "How can I set the slide valves of a locomotive when she is on the road?" J. H. S. asks: "What is the method of setting locomotive slide valves from marks on the slide spindle?" And F. O. asks: "How are the valves of inside cylinder locomotives set, since the back ports are out of sight and you cannot measure the lead?"
Our correspondent will find these questions answered in full below.
It is presumed that the lengths of the eccentric rod, reverse rod, and other parts are correct, and they are properly connected and oiled so as to be in working order. The first thing to do is to place the reverse lever in the forward full-gear notch of the quadrants, or sectors, as they are sometimes called. The next procedure is to place the crank on its forward dead center as near as can be ascertained by the eye, and loosening the set screw of the forward eccentric, that is to say, the eccentric which connects with the upper end of the link, move that eccentric round on the shaft until the valve leaves the port at the front end of the cylinder open to the amount of whatever lead it is desired to give the valve. In moving the eccentric round on the shaft, it is necessary to move it in the direction in which it will turn when in operation. This is done in order to take up any lost motion there may be in the eccentric straps, in the eccentric rod eyebolts, or other working parts or joints between the eccentric and the slide valve rod or spindle. If the eccentric was turned backward instead of forward, all the lost motion would operate to vitiate the set of the valve, because, when the eccentric begins to move, its motion will have no effect in moving the slide valve spindle, until all the lost motion in the various parts is taken up by the eccentric movement. In considering this part of the operation, we must bear in mind that, to set the valve, we must move the wheels of the engine, it being impracticable to move the piston itself. Now, in moving the wheels, we are confronted with the fact that the crank pin is pulling the connecting rod; hence, if there is any lost motion in the brasses at either end of the connecting rod, the piston will not be at the end of its stroke when the crank is on its dead center.
Suppose, for instance, that we have moved the driving wheel forward until the crank stands upright at a right angle to the bore of the cylinder, the resistance to motion of the piston and crosshead has caused the crank pin to bed against the half-brass nearest to the cylinder, all the play or lost motion is then between the other half-brass and the crank pin. When, however, the engine is at work and the piston is driving the crank pin, instead of being driven by it, the lost motion will exist between the crank pin and the half-brass nearest to the cylinder, and the contact will exist between the crank pin and the other brass. The difference in the position of the piston, caused by this lost motion, may be ascertained by moving the piston back and forth until the crank pin contacts with first one and then the other half-brass. It is sometimes attempted to remedy the defect due to this lost motion by moving the crank pin past the dead center and then moving it back to the dead center, so that while on that center the play or lost motion in the connecting rod is taken up. This is all very well so far as the connecting rod and piston is concerned, and will cause them both to stand on their respective dead centers with the lost motion taken up; but, in moving the wheel back to the dead center, we have given full liberty to all the lost motion in the various parts of the valve motion or gear, as already explained, in reference to moving the eccentric upon the shaft. As there are so many more parts in the valve gear, in which lost motion may occur, it is manifestly preferable to take up that play by moving the driving wheel in a continuous direction, rather than to move the latter back to accommodate any play there may be in the connecting rod.
The crank being placed by the eye upon its forward dead center, and the eccentric connected to the top of the link being moved round on the axle (in the direction in which the wheels will run when the engine is going forward) until the steam port at the front end of the cylinder is open to the amount of the lead, we fasten the eccentric to hold in that position. We then throw the reverse lever over into the last notch at the other end of the sector, lifting the link up so that the eccentric connected to the lower end of the link may be approximately adjusted, which is done by moving the eccentric round upon the axle (in the direction in which the axle will revolve when the engine is running backward) until the crank stands upon the same dead center, and the front port is open to the amount of the lead. This being done, we have the eccentrics approximately adjusted and may proceed to the final adjustment, in which the first thing to do is to find the exact dead centers of the crank. It is obvious that a line drawn through the center of the crank pin and the center of the wheel axle, will stand horizontally true and level when the crank is on either of the dead centers, but the presence of the crank pin makes it impracticable to draw such a line. We can therefore draw one which will be parallel to those centers; and to do this we draw a circle upon the end of the wheel axle (and from its center) of the same diameter as that of the crank pin, and then resting a straight-edge upon the bearing of the crank pin (taking care to avoid the round corner upon the pin, if there is one), we place the other end of the straight-edge even with the top of the circle drawn upon the axle; and then, using the straight-edge as a guide, we draw a line across the end of the axle and the wheel face. When this line is level the crank will be upon its dead center. This plan is sometimes employed, but is not a very accurate one, because the length of the line is very short as compared to the circumference of the driving wheel; hence, an error of the thickness of the line becomes one equal to several thicknesses of the line when carried out to the wheel circumference. Furthermore, if the line of the cylinder does not stand horizontally level, as is sometimes the case, the result of the whole proceeding will be inaccurate. Again, the connecting rod end and the coupling rod is in the way, rendering it awkward to both draw and level the line.
A better and more accurate method to find the dead centers is as follows: Place the reverse lever into the end notch of the sector at the forward end, and then move the driving wheel forward until the guide block is within about a quarter of an inch of the end of its travel, then place a straight-edge against the end of the guide block, and draw, on the outside face of the guide bar, a line even with the end of the guide block. Bend a piece of wire (pointed at both ends) to a right angle, make a center punch mark either in the rail, under the driving wheel, or in some stationary, solid part contiguous to the wheel, or at such distance from it that when one end of the bent wire is placed in the center punch mark, the operator with the other end will be able to draw a line across the rim of the driving wheel. Here, however, arises another consideration, that it is better to set the valves with the wheel axle in its proper position in the pedestal shoes, and in order to do this the wheel should rest upon the rail with its proper proportion of the weight of the engine resting upon it. The springs will then be deflected to their proper amount, and the axle box will have passed its proper distance up the pedestals. It is obvious that if the engine is blocked up so that the driving wheels clear the rails (which is done in order to avoid having the weight of the engine to move while setting the valve), the axle boxes will drop in the pedestal and the valve will be set incorrectly, as the wheels are in a wrong position. To avoid this, and at the same time to avoid having to move the whole engine while setting the valve, the engine is blocked up from the rails, and the axle boxes of the driving wheels are wedged up so as to be lifted up into their proper position. In this case there is no very accurate means of ascertaining what is the exact proper height, save it be by first marking upon the outside faces of the shoes or pedestal a line even with the top of the axle box when the load is upon the wheels, and then, after blocking up the engine from the rails, wedging up the axle boxes till the face again comes even with the line.
Whatever plan is pursued, one end of the piece of wire is rested in the fixed center punch mark, and with the other a line is drawn across the outside face of the wheel rim. The driving wheel is then revolved forward until the guide block returns, having passed to the end of its travel. When its end again stands exactly even with the mark made upon the guide bar, the piece of wire is again brought into requisition, one end being rested in the fixed center punch mark as before, and with the other end another line is drawn across the outside rim of the wheel. It is obvious that by taking a pair of compasses and finding a point exactly equidistant between the two lines thus marked upon the wheel rim, and then marking that point with a center punch mark, the crank will be upon its exact dead center, when one end of the piece of bent wire rests in the fixed center punch mark, the other end rests in the center punch mark upon the wheel rim. To find the other dead center, the wheel must be moved about halfway round and the process repeated with the motion block at the other end of the guide bars.
Thus, whenever the piece of wire will stand with one end resting in the fixed center punch mark and the other end in either of the center punch marks upon the wheel run, the crank is upon a dead center. Having thus placed the crank upon either dead center, we measure the valve lead, and if in temporarily fixing our eccentrics we gave it too much lead, we mark where it stands upon the shaft by means of a line drawn on the axle and carried up on the side face of the eccentric; then move the eccentric back some little distance more than is necessary to make the adjustment, and then move it forward again a little at a time, noting when the valve has the proper amount of lead, and thus fasten the eccentric upon the axle by means of the set screw.
The object of moving the eccentric too far back and then moving it forward is to make the adjustment so that the latter may be made with the lost motion of the valve gear all taken up. The next proceeding is to move the driving wheel halfway round and try the lead at that end of the stroke. If the lead at the two ends is not equal, it shows that either the slide valve spindle or the eccentric rods are not of the proper length and must be rectified; this being done, the crank must be again placed upon first one and then the other dead center, the valve lead being measured at each end. When the lead is equal at each end, the rods are of correct length, and the amount of the lead must be regulated by moving the eccentrics as already directed.
If the link block does not come opposite the end of the eccentric rod when the reverse lever is in the end notch of the sector, the length of the reverse rod is wrong and should be corrected. If the link block comes right, under the above conditions, for the forward but not for the backward eccentric rod, the notches in the sector are not cut in their proper positions, or the link hanger is not of the proper length. In either case the error may be remedied by altering the length of the latter. But, as doing this would alter the amount of the valve lead, it is well, if there is any prospect of such errors, to correct them before setting the valves.