Chapter 8

A new system of equipment of such lines is now being introduced into this country by Mr. Arthur Koppel, of 96 Leadenhall Street, E. C. The keynote of this system is flexibility, the arrangements being such that extensions or alterations can be readily effected. In fact, the line is portable, and it is claimed also to be cheaper than the ordinary construction. The overhead conductor is employed, as can be seen from Fig. 1, which gives a general view of a locomotive and train of skips on a line actually at work abroad. The supports for the wire are not provided by separate posts and brackets in the usual way, but by arched carriers attached to the sections of railway line, thereby forming a portable section of the electric railway, as illustrated by Fig. 2. The steel carrier or "arch" is fixed to one of the sleepers, which is made of sufficient length for that purpose. On the straight line these line supports are placed about 25 yards apart. In curves of a small radius each section of tramway is provided with an arch, to keep the line of the wire as nearly as possible parallel to the curve of the line. Apart from these special extended sleepers with wire carriers attached, the line is constructed in the ordinary mariner with rails 14 lb. per yard and upward. As the electric locomotives are lighter than steam locomotives, the weight of rail required is somewhat less. The special trolley for erecting the wires along the railway line is shown in Fig. 3. This consists of an ordinary four wheeled platform wagon with ladder, and wire drum with tightening gear and clamps or grips for anchoring the trolley to the line. The wire is led over a sheave on top of the ladder and fixed to the picket post at the beginning of the line. When erecting the wire the trolley is pushed beyond the first carrier arch, clamped on to the rails, and the wire is then tightened by means of the tightening gear. It is then firmly fixed to the insulator on the carrier arch The tension in the copper wire is taken up by a second portable ladder, which is also provided with a tightening gear and can be clamped to the rails in the same manner as the trolley, so that the trolley can then be pushed behind the second carrier arch and the process previously described repeated. By the tension in the wire the carrier arches acquire the necessary stability, while without the procedure previously described it would be impossible to use such light arches attached to the sleepers. On permanent lines, the extreme ends of the wire are attached to properly anchored picket posts. On portable lines, on the other hand, the trolley with the wire drum is fixed to the rails at the end of the line, as shown in Fig. 3, so as to enable the line to be lengthened or shortened, as may be required, with ease.

Care is taken in insulating the drum and ladders so as to prevent leakage from this erecting trolley to earth. The feeders from the power house to the overhead wire and to the rails respectively are erected on light iron posts, which have also been standardized by Mr. Koppel. A specimen of these posts with an anchored stay is shown in Fig. 4. All these details are arranged for convenience of the contractor required to rapidly equip a line of railway, which can also be removed as soon as the work has been done.

The locomotive used is varied in form with the gage of the line, but we are particularly concerned with those for gages under 24 inches. One form of such locomotive without a hood to protect the driver is shown in Fig. 5. In this locomotive the gear is the same as that of the next illustration, but it is securely boxed in a watertight iron cover. The controlling gear is then placed vertically in front. Figs. 6 and 7 show the details of the electrical and mechanical parts of this locomotive when fitted with a platform at either end, and with a hood. The motor. M, is of the internal pole type, and is supported on the underframe of the wagon. A double gear is used. The first is a spur gearing, connecting the motor to a countershaft placed under the motor. This gear reduces the speed of rotation to about 200 revolutions. The countershaft is then connected to the two axles of the trolley by chain gearing. This gives the necessary flexibility between the car body and the wheel required, as the springs give to any inequality of the rails. In this gearing there is no change of speed. The underframe is provided with spring axle boxes, and also with spring buffers and drawbars. The speed of the motor can be regulated within very wide limits by the regulator, R. An effective hand brake is also provided.

For gages of 20 inches and upward the motors can be mounted on springs and attached to the running axles inside of the wagon underframe. This construction is particularly recommended by Mr. Koppel where, in order to mount heavy gradients, the dead load of the motor car must be assisted by the paying load to produce the necessary adhesion. In such cases several motor wagons would be used in the same train. As regards the working voltage, this can be varied to suit special requirements, but the locomotive we illustrate was designed for 110 volts. At this pressure its possible working speed was at least eight miles per hour. The supply of power is also a matter not referred to particularly, as in many cases a lighting plant is used by the contractors, which could also be employed to provide the necessary energy for the electric railway. The good work done by small electric locomotives in the excavation work for the Waterloo and City Railway[1] will convince our large contractors of the valuable service which electricity can render both above and below ground.--The Electrical Engineer.

[Footnote 1: Electrical Engineer, vol. xvi., p. 499.]

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A connection between Servian and Roumanian railways is to be established by bridging the Danube. It is reported proposals have already been made to the governments interested, by the Union Bridge Company, also by British and French constructors.--Uhland's Wochenschrift.

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LIQUID RHEOSTATS.

BY H. S. WEBB.[1]

[Footnote 1: In American Electrician.]

The object in view when the following tests were commenced was to obtain some data from which the dimensions of a liquid rheostat for the dissipation as heat of a given amount of energy could be calculated, or at least estimated, when the maximum current and E.M.F. are known. These tests were rather hastily made and are far from being as complete as I should like to have them, and are published only to answer some inquiries for information on the subject.

In the first test, an ordinary Daniell jar (6¼ inches in diameter by 8 inches deep) with horizontal sheet iron electrodes was filled with tap water. It would not carry 4 amperes for over fifteen or twenty minutes, although the jar was full of water and the plates only ¾ inch apart. After that length of time it became too hot, causing great variation in the current on account of the large amount of gas liberated, much of which adhered to the under surface of the upper electrode. The difference of potential between the plates was 200 volts.

A run was made with 1 ampere and then with 2 amperes for one hour. In the latter case the voltage between the electrodes was about 71 volts and the temperature rose to about 167° F.

From these tests it would be safe to allow a vessel with a cross section of 30.7 square inches to carry from 2 to 2½ amperes when tap water and horizontal electrodes are used.

In test No. 2 the same jar and electrodes were used as in the preceding test, but the tap water was replaced by a saturated solution of salt water. Eleven amperes with a potential difference of 7 volts between the electrodes, which were 7¾ inches apart, were passed through the solution for three hours, and the temperature at the end of the run was 122° F., and was rising very slowly.

Although the current per square inch is much greater, the watts absorbed per cubic inch is much less in this case than when water was used. With the water carrying 2 amperes the watts absorbed would be over 10 per cubic inch, while for the saturated solution of salt when carrying 11 amperes it would be only about 0.4 watt.

In test No. 3 use was made of a long, wooden rectangular trough (42 inches by 6½ inches by 8 inches) with vertical, sheet iron electrodes. The cross section of the liquid, which was a 10 per cent. solution of salt in water, was 44 square inches, and with 10 amperes passing through the solution for 1¾ hours the temperature rose to 95° F., and was rising slowly at the end of the run.

The plates were 41¾ inches apart, and at the end of the run the voltmeter across the terminals read 20. This gives a current density of nearly ¼ ampere per square inch and 0.11 watt per cubic inch. These values are too low to be considered maximum values, for this cross section of a 10 per cent. salt solution would probably carry 13 to 15 amperes safely.

It appears that as the amount of salt in the solution is increased from zero to saturation, the maximum current carrying capacity is increased, but the watts absorbed per cubic inch are less.

A very small addition of salt to tap water makes the solution a much better conductor than the water, and reduces greatly the safe maximum watts absorbed. In using glass vessels, such as Daniell jars, there is danger of cracking the jar if the temperature rises much above 165° to 175° F.

In test No. 4 an ordinary whisky barrel, filled up with tap water, was used. Two horizontal circular iron plates (3/16 inch thick) were used for electrodes. The diameter of the inside of the barrel was approximately 19-1/2 inches. With the two plates 26-3/8 inches apart a difference of potential of 486 volts gave a current of 2.6 amperes. With the plates 7/8 inch apart, 228 volts gave 35.5 amperes at the end of one hour, when all the water in the barrel was very hot (175° F.), and there was quite a good deal of gas given off. The current density in this case was about 0.12 ampere per square inch and the watts absorbed 30.5 per cubic inch. If it were not for the large amount of water above both electrodes, it is doubtful if this current density could have been maintained.

In test No. 5 a rectangular box, in which were placed two vertical sheet iron plates, was filled with tap water. The distance between the plates was 5/8 inch, and with a difference of potential of 414 at start and 397 at end of the run, a current of 35 amperes was kept flowing for 35 minutes. Cold tap water was kept running in between the electrodes at the rate of 6.11 pounds per minute (about 1/10 cubic foot) by means of a small rubber tube about 1/4 inch inside diameter. This test is very interesting in comparison with the preceding. The current carrying capacity, 0.3 ampere per square inch, was more than double, and the energy absorbed 183 watts per cubic inch, more than six times as great as in case where running water was not used.

The temperature in some places between the plates occasionally rose as high as 205° F., and it was necessary, in order to avoid too violent ebullition, to keep the inflowing stream of water directed along the water surface between the two plates. Less water would not have been sufficient, and, of course, by using more water, the temperature could have been kept lower, or with the same temperature the watts absorbed could have been increased.

When a large current density is used, there is considerable decomposition of the iron electrodes when either salt or pure water is used, and in the case of horizontal electrodes, the under surface of the top plate may become covered with bubbles of gas, making the resistance between the plates quite variable. For large current density a horizontal top plate is not advisable, unless a large number of holes are drilled through it. A better form for the top electrode would be a hollow cylinder long enough to give sufficient surface. Washing soda is often a convenient substance to use instead of salt.

If, from experience, the size of a liquid rheostat for absorbing a given amount of energy cannot be estimated, the dimensions may be calculated approximately as follows:

Suppose, for instance, it is desired to absorb 60 amperes at 40 volts difference of potential between the electrodes. Now, it is inconvenient to obtain a saturated solution of salt, and to use tap water would require too large a cross section--especially if a barrel or trough is to be used--in order to have the resistance with the plates at a safe distance apart, small enough to give 60 amperes with 40 volts.

Let us try a 10 per cent. solution of salt. Suppose the maximum current this will carry is ¼ ampere per square inch, which will give a cross section of the solution of at least 60 ÷ ¼ = 240 square inches. Now, the specific resistance per inch cube (i.e., the resistance between two opposite surfaces of a cube whose side measures 1 inch) of the 10 per cent. solution of salt used in test No. 3 was 2.12 ohms. The drop, CR, will be 2.12 × ¼ = 0.53 volt per inch length of solution between electrodes. Hence, the electrodes will have to be 40/0.53 = 75 inches apart. This would require about three barrels connected in series. This was taken merely as an illustration, because its specific resistance was known when the current density was ¼ ampere per square inch. This solution, however, will carry safely 1/3 ampere per square inch, but I used the previous figure, since I did not know its specific resistance for this current density, because its specific resistance will be lower for a larger current density on account of the higher temperature which it will have, for the resistance of a solution decreases as its temperature increases.

To reduce this length would require a solution of higher specific resistance, that is, a solution containing less than 10 per cent. of salt, and an increase in the cross section, since the maximum carrying capacity also diminishes as the percentage of salt diminishes. Only approximate calculations are useful because variations in temperature, amount of salt actually in solution and the rate at which heat can be radiated, all combine to give results which may vary widely from those calculated.

As a matter of fact, it is seldom necessary or advisable to use a solution containing over 2 or 3 per cent. of salt. The best way to add salt to a liquid rheostat is to make a strong solution in a separate vessel and add as much of this solution as is needed. This avoids the annoying increase in conductivity of the solution which happens when the salt itself is added and is gradually dissolved.

Liquid rheostats are ever so much more satisfactory for alternating than for direct current testing. The electrodes and solution are practically free from decomposition, and a given cross section seems to be able to carry a larger alternating than direct current--probably due partly to the absence of the scum on the surface which hinders the radiation of heat.

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THE PROGRESS OF MEDICAL EDUCATION IN THE UNITED STATES.

A retrospective survey of the progress made and of the reforms instituted in medical education in the United States is instructive. In many respects there is cause for much congratulation, while for other reasons the situation gives rise to feelings of alarm. It is pleasing to note and it augurs well for the future that a decided advance has been made in the direction of a more thorough medical training, yet at the same time it is discouraging to observe that, despite these progressive steps, competition does not abate, but rather daily becomes more acute. Dr. William T. Slayton has just issued his small annual volume on "Medical Education and Registration in the United States and Canada." From a study of this book, which fairly bristles with facts, a sufficiently comprehensive opinion may be formed in regard to the present state of medical education in this country. According to this work, there is now a grand total of one hundred and fifty-four medical schools. Of this number, one hundred and seventeen require attendance on four annual courses of lectures, and twenty-seven require attendance on sessions of eight months, and ten on nine months each year. Twenty-nine States and the District of Columbia require an examination for license to practice medicine; eighteen of these require both a diploma from a recognized college and an examination. Fifteen States require a diploma from a college recognized by them or an examination. Five States, viz., Vermont, Michigan, Kansas, Wyoming and Nevada, have practically no laws governing the practice of medicine; Alaska the same. In order to gain a clear comprehension of the existing state of affairs, a comparison of the number of students at two periods, with a lapse of years intervening sufficient to eliminate all minor variations, will be more to the point than merely regarding the multiplication of schools. Many of these mushroom institutions are not worthy of notice, containing perhaps a dozen students, and brought into existence only for the purpose of profit or from other motives of self-interest. The number of students is as reliable an index as can be given. For instance, taking the decade between 1883-84 and 1893-94, it will be found that the students in regular schools in 1883-84 numbered 10,600; in 1893-94 they had increased to 17,601. Students in homoeopathic schools in 1883-84 were 1,267; in 1893-94, 1,666. The number of eclectic students was stationary at the two periods. The increase during the period from 1893-94 to the present time has been at about the same ratio.

These figures reveal more plainly than words the existing condition of affairs, which must, too, in the nature of things, continue until that time when all the States fall into line and resolve to adopt a four years' course of not less than eight months.

To make yet another comparison, the total number of medical schools in Austria and Germany, with a population exceeding that of this country, is twenty-nine. Great Britain, with more than half the population, has seventeen; while Russia, with one hundred million inhabitants, has nine. Of course we do not argue that America, with her immense territory and scattered population, does not need greater facilities for the study of medicine than do thickly inhabited countries, as Germany and Great Britain; but we do contend that when a city of the size of St. Louis has as many schools as Russia, the craze for multiplying these schools is being carried to absurd and harmful lengths. However, that the number of schools and their yearly supply of graduates of medicine are far beyond the demand is perfectly well known to all. The Medical Record and other medical journals have fully discussed and insisted upon that point for a considerable time. The real question at issue is by what means to remedy or at least to lessen the bad effects of the system as quickly as possible. The first and most important steps toward this desirable consummation have been already taken, and when a four years' course comes into practice throughout the country, the difficult problem of checking excessive competition will at any rate be much nearer its solution. Why should France, Germany, Great Britain and other European nations consider that a course of from five to seven years is not too long to acquire a good knowledge of medical work, while in many parts of America two or three years' training is esteemed ample for the manufacture of a full-fledged doctor? Such methods are unfair both to the public and to the medical profession, and the result is that in numerous instances the short-time graduate has either to learn most of the practical part of his duties by hard experience, to starve, or to utilize his abilities in some more lucrative path of life. Taking into consideration the fact that the theory and practice of medicine have become so extended within recent years, it must be readily conceded that four years is barely sufficient time in which to gain a satisfactory insight into their various departments. For a person, however gifted, to hope to receive an adequate medical training in two or three years is vain.

In those States in which the facilities for securing a medical education are abundant, and where the time and money to be expended are within the reach everyone, there is always the danger that an undue proportion will forsake trade in order to join the profession. This is especially the case when times are bad. Many persons seem to be possessed of the idea that the practice of medicine as a means of livelihood should be regarded as a something to fall back upon when other resources fail. Accordingly, when trade is depressed and money is scarce, there is a rush to enter its ranks. That this view of the matter is altogether an erroneous one is too self-evident to need any demonstrative proof. Again, although the question of a universal four years' course is a most important one, it must not be forgotten that examination takes almost as conspicuous a place. It is desirable that every one entering on medical studies should possess a general education. With the exception of a few unimportant schools, the entrance examinations would appear to afford the necessary test. Then comes the much more vital point of how to gage, in the fairest possible manner, the extent of the medical knowledge of those who have undergone their full term of study. For various reasons the conducting of the final examinations by professors in the school in which the student has been taught is open to many and grave objections, more especially when these professors are themselves teachers in that school. As has been pointed out in The Medical Record on more than one occasion, the most obviously fair regulation is that of independent examination by an unbiased State board. If this plan were carried into execution, medical education in America generally would rest on a firmer basis than in Great Britain, in which country the standard, although nowhere so low as in parts of the United States, still varies very considerably in the different schools. The General Medical Council of England has arrived at the conclusion that competition must be checked, and has lately brought into force two drastic measures calculated to attain this object; one is the lengthening of the course to five years, and, more recently, the abolishing of the unqualified assistant. The medical profession of America is quite as conscious of the disastrous results of competition as are its fellow practitioners on the other side, and should use every legitimate means to sweep away the evils of the present system.--Medical Record.

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DEATHS UNDER ANÆSTHETICS.