Chapter 1

SCIENTIFIC AMERICAN SUPPLEMENT NO. 787

NEW YORK, January 31, 1891

Scientific American Supplement. Vol. XXXI., No. 787.

Scientific American established 1845

Scientific American Supplement, $5 a year.

Scientific American and Supplement, $7 a year.

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TABLE OF CONTENTS.

I. BIOGRAPHY.--CHARLES GOODYEAR.--The life and discoveries of the inventor of vulcanized India rubber, with portrait.--1 illustration

II. BIOLOGY.--Can we Separate Animals from Plants?--By ANDREW WILSON.--A debated point well discussed.--The bases on which distinctions must be drawn

III. ELECTRICITY.--A New Electric Ballistic Target.--A target for investigations of the velocity of projectiles, now in use at the United States Military Academy, West Point, N.Y.--1 illustration.

Electric Erygmascope.--An electric lighting apparatus for examining earth strata in bore holes for geologists' and prospectors' use.--1 illustration

The Electro-Magnet.--By Prof. SILVANUS THOMPSON.--Continuation of this exhaustive treatise, giving further details on special points of construction.--1 illustrations

IV. ENTOMOLOGY.--Potash Salts.--The use of potash salts as insecticides, with accounts of experiments

The Outlook for Applied Entomology.--By Dr. C.V. RILEY, U.S. entomologist.--The conclusion of Prof. Riley's lecture, treating of the branch of entomology with which his name is so honorably associated

V. INSURANCE.--The Expense Margin in Life Insurance.--Elaborate review of the necessary expenses of conducting the insurance of lives, with tables and calculations

VI. MATHEMATICS.--The Trisection of Any Angle.--By FREDERIC R. HONEY, Ph.B.--A very ingenious demonstration of this problem, based on the properties of conjugate hyperbolas

VII. METEOROLOGY.--Note on the Mt. Blanc Meteorological Station

The Flood at Karlsbad.--Account of the recent flood and of its destructive effects.--1 illustration

VIII. MECHANICAL ENGINEERING.--Station for Testing Agricultural Machines.--A proposed establishment for applying dynamometer tests to agricultural machines.--1 illustration

Steam Engine Valves.--By THOMAS HAWLEY.--A review of modern slide valve practice, the lap, cut-off, and other points.--6 illustrations

IX. MISCELLANEOUS.--Science in the Theater.--Curious examples of stage effect in fictitious mesmerizing and hypnotizing.--4 illustrations

Theatrical Water Plays.--Recent episodes in real water plays at Hengler's Circus, London.--2 illustrations

X. NAVAL ENGINEERING.--The French Ironclad War Ship Colbert.--An armored wood and iron ship, with central battery.--1 illustration

XI. PHYSIOLOGY AND HYGIENE.--Newer Physiology and Pathology.--By Prof. SAMUEL BELL. M.D.--An excellent presentation of modern practice in the light of bacteriology

Test Card Hints.--How to test the eyes for selecting eyeglasses and spectacles

The Composition of Koch's Lymph.--What Prof. Koch says it is and what it can do.--The cabled account of the disclosure so long waited for

XII. TECHNOLOGY.--Firing Points of Various Explosives.--The leading explosives, with the temperature of their exploding points tabulated

The Recovery of Gold and Silver from Plating and Gilding Solutions--A paper of interest to silver and gold platers, as well as photographers

Water Softening and Purifying Apparatus.--An apparatus for treatment of sewage, etc., chemically and by deposition.--1 illustration

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THE FRENCH IRONCLAD WAR SHIP COLBERT.

The central battery ironclad Colbert is one of the ten ships of the French navy that constitute the group ranking next in importance to the squadron of great turret ships, of which the Formidable is the largest. The group consists of six types, as follows:

1. The Ocean type; three vessels; the Marengo, Ocean, and Suffren. 2. The Friedland type, of which no others are built. 3. The Richelieu type, of which no others are built. 4. The Colbert type, of which there are two; the Colbert and the Trident. 5. The Redoubtable type, of which no others are built. 6. The Devastation type, of which no others are built.

The Colbert was launched at Brest in 1875, and her sister ship, the Trident, in 1876. Both are of iron and wood, and the following are the principal dimensions of the Colbert, which apply very closely to the Trident: She is 321 ft. 6 in. long, 59 ft. 6 in. beam, and 29 ft. 6 in. draught aft. Her displacement is 8,457 tons, her indicated horse power is 4,652, and her speed 14.4 knots. She has coal carrying capacity for 700 tons, and her crew numbers 706. The thickness of her armor belt is 8.66 in., that protecting the central battery is 6.29 in. thick, which is also the thickness of the transverse armored bulkheads, while the deck is 0.43 in. in thickness. The armament of the Colbert consists of eight 10.63 in. guns, two 9.45 in., six 5.51 in., two quick firing guns, and fourteen revolving and machine guns.--_Engineering._

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A compound locomotive, built by the Rhode Island Locomotive Works, has been tried on the Union Elevated Railroad, Brooklyn, N.Y. The engine can be run either single or compound. The economy in fuel was 37.7 per cent, and in water 23.8 per cent, over a simple engine which was tested at the same time. The smoothness of running and the stillness and comparative absence of cinders was fully demonstrated.

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STEAM ENGINE VALVES.

[Footnote: Lecture delivered at Wells Memorial Institute, Boston, in the Lowell Free Course for Engineers. From report in the _Boston Journal of Commerce_.]

By THOMAS HAWLEY.

RIDING CUT-OFF VALVES--PECULIARITIES AND MERITS OF THE DIFFERENT STYLES.

In considering the slide valve in its simple form with or without lap, we find there are certain limitations to its use as a valve that would give the best results. The limitation of most importance is that its construction will not allow of the proper cut off to obtain all the benefits of expansion without hindering the perfect action of the valve in other particulars. At this economical cut off the opening of the steam port is very little and very narrow, and although this is attempted to be overcome by exceedingly wide ports, sixteen inches in width in many cases in locomotive work, this great width adds largely to the unbalanced area of the valve. The exhausting functions of the valve are materially changed at the short cut off, and when much lap is added to overcome this defect, there usually takes place a choking of the exhaust port. You might inquire, why not make the port wider, but this would increase the minimum amount of load on the valve, and this must not be overlooked. Then the cut off is a fixed one, and we can govern only by throttling the pressure we have raised in the boiler or by using a cut off governor and the consequent wastes of an enormous clearance space. You will observe, therefore, that the plain slide valve engine gives the most general satisfaction at about two-thirds cut off and a very low economic result. The best of such engines will require forty-five to fifty pounds of steam per horse power per hour, and to generate this, assuming an evaporation of nine pounds of water to a pound of coal, would require between five and six pounds of coal per horse power per hour. And the only feature that the valve has specially to commend it is its extreme simplicity and the very little mechanism required to operate it.

Yet this is of considerable importance, and in consideration of some special features at its latest cut off, the attempt has been many times made to take advantage of these features. For instance, at 90° advance, the valve opens very rapidly indeed and fully satisfies our requirements of a perfect valve. This is one good point, and in this position also the exhaust and compression can be regulated very closely and as desired without much lap, and as the opening of the exhaust port comes with the eccentric at its most rapid movement the release is very quick and as we would have it. This is only possible at the most uneconomic position of the valve as regards cut off.

The aim of many engineers has been to take advantage of these matters by using the valve with 90° angular advance of eccentric ahead of crank, for the admission, release, and compression of the steam, and provide another means of cutting off, besides the one already referred to, viz., cutting off the supply of steam to the chest, and overcome the objection in this one of large clearance spaces. This is done by means of riding cut off valves, often called expansion valves, of which, perhaps, the most widely known types in this vicinity are the Kendall & Roberts engine and the Buckeye. The former is used in the simplest form of riding cut off, while the Buckeye has many peculiar features that engineers, I find, are too prone to overlook in a casual examination of the engine. In these uses of the slide valve, too, means are suggested and carried out of practically balancing the valve.

The origin of the riding cut off is most generally attributed to Gonzenbach. His arrangement had two steam chests, the lower one provided with the ordinary slide valve of late cut off, and steam was cut off from this steam chest by the expansion valve covering the ports connecting with the upper steam chest. This had the old disadvantage that all the steam in the lower chest expanded with that in the cylinder, at a consequent considerable loss. This was further improved by causing the riding cut off to be upon the top of the main valve, instead of its chest, and resulted in a considerable reduction of the clearance space.

This is the simplest form, and is shown in Fig. 1. The steam is supplied by a passage through the main valve which operates exactly as an ordinary slide valve would. That is, the inside edges of the steam passage are the same as the ordinary valve, the additional piece on each end, if I may so term it, being merely to provide a passage for the steam which can be closed, instead of allowing the steam to pass the edge. The eccentric of the main valve is fastened to the shaft to give the proper amount of lead, and the desired release and compression, and the expansion valve is operated by a separate eccentric fastened in line with or 180° ahead of the crank. When the piston, therefore, commences to move from the crank end to open the port, D, the expansion valve is forced by its eccentric in the opposite direction, and is closing the steam port and would have closed it before the piston reached quarter stroke, thus allowing the steam then in the cylinder to do work by expansion. The eccentric operating this expansion valve may be set to close this steam port at any point in the stroke that is desired, the closing occurring when the expansion valve has covered the steam port. Continuing the movements of the valves, the two would move together until one or the other reached its dead center, when the movements would be in opposite directions.

There are three ways of effecting the cut off in such engines, the main valve meanwhile being undisturbed, its eccentric fastened securely so as not to disturb the points of lead, release, and compression. All that is required is to cause the edge of the expansion valve to cover the steam port earlier in the stroke, and this can be done, first, by increasing the angular advance of the cut off eccentric; second, by adding lap to the cut off valve; and third by changing the throw of the eccentric. In all these instances the riding valve is caused to reach the edge of the steam port earlier in the stroke. We will take first, as the simplest, those methods by which the lap of the cut off valve is increased.

It will be noted that there is but one edge of this valve that is required to do any work, and that is to close the valve. The eccentrics are so placed that the passage in the main valve is opened long before the main valve itself is ready to admit steam to the cylinder, so that only the outer edges are the ones to be considered, and it will be readily seen that the two valves traveling in opposite directions, any lap added to the working edge of the cut off valve will cause it to reach the edge and therefore close the port earlier than it would if there was less lap. And we might carry it to the extreme that we could add lap enough that the steam passage would not be opened at all.

In Fig. 2 is shown the method by which this is accomplished, in what is called Meyer's valve, and such as is used in the Kendall & Roberts engine. We have only one point to look after, the cut off, so we can add all the lap we wish without disturbing anything else. In this engine the lap is changed by hand by means of a little hand wheel on a stem that extends out of the rear of the steam chest. The valve is in two sections, and when it is desired to cut off earlier, the hand wheel is turned in such a direction that the right and left hand screws controlling the cut off valve move one valve portion back and the other forward, which would, if they were one valve and they should be so considered, have the effect of lengthening them, or adding lap to them. The result would be that the riding valve would reach the edge of the steam port earlier in the stroke, bringing about an earlier cut off. If the cut off is desired to be later, the hand wheel is so turned that the right and left hand screws will bring the valve sections nearer together, thus practically taking off lap. Now this may be done by hand or it may be done by the action of a governor.

In the latter case the governor at each change of load turns the right and left hand screws to add or take away lap, as the load demands an earlier or later cut off; in other cases the governor moves a rack in mesh with a gear by which the valve sections are brought closer together or are separated. The difficulty with the case where the hand wheel is turned by hand is that the cut off is fixed where you leave it, and governing can only be at the throttle. For this reason anywhere near full boiler pressure would not be obtained in the cylinder of the engine. If the load was a constant one, and the cut off could be fixed at about one-third, causing the throttle to open its widest, very good results would be obtained, but there is no margin left for governing.

If the load should increase at such a time the governor could not control it under these conditions, and it would lead to a decrease in speed unless the lap was again changed to give a later cut off. On this account the general practice soon becomes to leave the cut off at the later point and give range to the throttle, and we come back once more to the plain slide valve cutting off at half stroke, and the only gain there is, is in a quick port opening and quick cut off. But these matters are more than offset by the wire drawing between the steam pipe and chest, through the throttle, and the fact that there is added to the friction of the engine the friction of this additional slide valve and a considerable liability to have a leaky valve.

In the case where the governor changes the position of the cut off valve a greater decree of economy would result. In this engine, of which the Lambertville engine is a type, the main valve is a long D slide, with multiple ports at the ends through which the steam enters the cylinders. It is operated from an eccentric on the crank shaft in the usual manner. The cut off valve is also operated from the motion on an eccentric fixed upon the crank shaft. The rod or stem of the cut off valve passes through the main valve rod and slide. Upon the outer end of the cut off valve rod are tappets fastened to engage with tappets on the eccentric valve rod. Connection between the cut off eccentric, therefore, and the cut off valve is only by means of the engagement of these tappets. The eccentric rod is fastened to a rocker arm having motion swinging about a pin or bearing in the governor slide, which may be raised or lowered by a cam operated by the governor. The cut off slide is of cylindrical shape and incloses a spring and dash pot with disks attached by means of which the valve is closed. The motion for operating the valves is relatively in the same direction, the cut off eccentric having the greatest throw and greater angular advance to cause it to open earlier and quickly before the main valve is ready to admit steam. The cut off eccentric rod swinging the rocker arm, the tappets thereon engage with those upon the cut off valve rod and open the passages to the main valve, and in their movement compress the spring in the main valve. According as the speed of the engine, the rock arm will be raised or lowered so that the tappets upon the eccentric rod may keep in engagement a shorter or longer time before they disengage, thus allowing the spring that has been compressed by the movement of the cut off valve to close that valve quickly and the supply of steam to the engine, the cut off valve traveling with the main valve for the balance of the stroke. This device will give a remarkably quick opening and a quick cut off, but in view of the fact that the governor has so much to do, its delicacy is impaired and a quick response to the demands of the load changing not so likely to occur. The cut off cannot be as quick as in some other engines, because the valves are moving in opposite directions, and while this fact would help, so far as shortening the distance to be traveled before cut off, the resistance of the valves to travel in opposite directions, or rather the tendency of the valve to travel with the main valve, hinders its rapid action.

This is one great objection to the rack and gear operated by the governor, that two flat valves riding upon each other and sliding in opposite directions at times require a considerable amount of force to move them, and as only a slight change in load is required by the load, the governor cannot handle the work as delicately as it should. It is too much for the governor to do well. To overcome this difficulty the Ryder cut-off, shown in Fig. 3, was made by the Delamater people, of New York. The main slide valve is hollowed in the back and the ports cut diagonally across the valve to form almost a letter V. The expansion valve is V-shaped, and circular to fit its circular-seat. The valve rod of the expansion valve has a sector upon it and operated by a gear upon the governor stem, which rotates the valve rod, and the edge of the valve rod is brought farther over the steam port, thus practically adding lap to the valve. Little movement is found necessary to make the ordinary change in cut-off, and it is found to be much easier to move the riding valve across the valve than in a direction directly opposite. It would require considerable force to move the upper valve by the governor faster than the lower, or in a direction opposite to that in which it is moving, but very little force applied sideways at the same time it is moving forward will give it a sideways motion. In this device the governor has only to exert this side pressure and therefore has less to do than if it were called upon to move the upper valve directly against the movement of the lower.

Something similar is the valve of the Woodbury engine, of Rochester, N.Y. The cut-off valve is cylindrical, covering diagonal ports directly opposite, and is caused to be rotated by the action of the governor that operates a rack in mesh with a segment. Very little movement will effect a considerable change in the lappage of the valve, the valve turning about one-quarter a revolution for the extremes of cut off. The cut off valve rod works through a bracket and its end terminates in a ball in a socket on the end of the eccentric rod. In this case the governor has not as much to do as in other instances.

Still another method of effecting this change in cut off, but hardly by increasing the lap of the valve, is shown in the next drawing, Fig. 4. The cut off valve is held upon the main valve by the pressure of steam upon its back and rides with it until it comes in contact with the cut off wedge-shaped blocks, when its motion is arrested, and the main valve continuing its movement the steam port is closed by the main valve passing beneath the cut off valve. Thus the main valve travels and carries the cut off valve upon its back again until the cut off valve strikes the wedge on the other end and the cut off is effected. The relative positions of the blocks are determined by the governor, that will raise or lower them so that the cut off valve will engage with them earlier or later as desired. This device was designed specially as an inexpensive method of changing the common slide valve into an automatic cut off. The cut off would not be as quick as in other cases we have cited, depending here upon the movement of the lower valve alone, and that, too, is in its slowest movement; whereas in the other cases, the edges approaching each other, by the differing movement of the valves the cut off is very rapid, provided the distance to travel is not long. In this device considerable noise must result by the cut off valve striking the cut off blocks, and a considerable amount of leakage is likely to occur past this valve.

But there is one great objection in the valve gears thus far cited, that the travel of the expansion valve upon the main valve is variable. I have in mind the case of a Kendall & Roberts engine, which had been run for a long time at no better economy than would be obtained from a plain slide valve engine, and when it was attempted to get an earlier cut off by separating the two cut off valves, they had worn so much in their old place on the valve that shoulders were found sufficient to cause a disagreeable noise and a leaky valve. This is very apt to occur, not only where the valve is run for a long time on one seat, but in cases of variation of the travel of the expansion valve. The result is that a change will bring about a leaky valve, something that every engineer abhors.

The construction of the Buckeye engine, which is also of this type, is such that the travel of the valve on the back of the main valve is always the same, no matter what the cut off may be. Then this engine makes use of our second proposition as a means of effecting the cut off, viz., by advancing the eccentric. You will readily observe that anything that will cause the cut off valve to reach a certain point earlier in the stroke will bring about an earlier cut off as it hastens everything all around. This is the plan pursued in the Buckeye, in which the governor, of the shaft type, turns the eccentric forward or back according as the load demands. Then, in addition, the valve is balanced partially, the attempt not being made to produce an absolutely balanced valve, on the ground that there should be friction enough to keep the surfaces bright and to prevent leakage. The most perfect valve will, of course, be entirely balanced under all conditions of pressure so as to move with perfect ease. With the riding cut off valve in connection with the plain slide valve, this is not accomplished, and it does not matter whether it is partially unbalanced to prevent leakage or not, the fact that it is not entirely balanced prevents it reaching the ideal valve.