There are three places in the injector to which we will call attention in examining the action of a particle of steam; (a) in the boiler, (b) in the vacuum chamber, (c) in the mixed column of water and steam. At a the steam is practically in a state of rest, but possesses energy capable of doing work. In passing from a to b work is done in giving to the steam a high velocity, so that at b it possesses a large portion of kinetic energy by virtue of which it strikes the water a blow and sets it in motion. Suppose now that the steam, having a velocity v, strikes, say, fifteen times its mass of water and sets it in motion, the combined mass will have a velocity of only one-sixteenth of v, because the momentum before impact, v X 1, must be equal to that after impact, v 16 X (1 + 15). The kinetic energy possessed by the steam before impact is equal to § × v2 but afterward there will be no more then 1+15×

2

v2

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so that at impact fifteen-sixteenths of the kinetic energy of the steam disappears, being retransformed into heat by the concussion, it will thus be seen that the injector does primarily transform a large amount of heat into work, but that it uses this work in so uneconomical a way, in forcing the water into the boiler by impact, that most of it is wasted as mechanical work, though saved as heat.

NOVEL FORM OF ELECTRO-MAGNETIC TELEPHONE. By Prof. R. B. FULTON, University, Mississippi.

[ABSTRACT.]

THE author has devised a form of electro-magnetic telephone, which may be used as a receiver or transmitter, in which the lines of magnetic force, the direction of the induced currents, and the direction of the movement of the vibrating parts are each at right angles to the other two. This end is attained by dispensing with the ordinary spool electro-maguet and circular diaphragm.

A tube of thin sheet iron, open at one or both ends, having a polygonal cross section, is magnetized, and has ordinary fine insulated telpehone wire coiled around the outside, the coils being each in a plane perpendicular to the length of the tube. One end of the tube is made a north, and the other a south pole. The coils are placed over those parts of the walls of the tube which are thrown into vibration when the tube is spoken into. The best results seem to be obtained with the above instrument as a transmitter, and the ordinary Bell receiver.

A NEW PRESSURE INDICATOR OR RECORDER (EXPERIMENTAL MODEL). By Prof. W. H. BRISTOL, Stevens Institute, Hoboken, N. J.

[ABSTRACT.]

In this instrument the novelty consists in employing a special form of the well-known Bourdon spring tube in combination with a principle involved in the construction of a pressure indicator which was invented and

patented by Jno. Matthews in 1855. With such a combination it was found to be possible to produce a pressure indicator in which the movement of the registering pointer is positive and of such range for given variations that the usual or all multiplying devices may be dispensed with. The invention of Matthews consisted in making a tube of copper by electric deposition, of circular cross section with one side corrugated. One end being closed, an internal pressure produced an elongation of the corrugated side which, being restrained by the straight side resulted in a bending of the tube, the amount of bending depending upon the pressure. The deflections produced as described are then multiplied to suit the range of reading required.

In the self-registering instrument exhibited the tube has a flattened cross section, is closed at one end, and bent into an approximately sinusoidal form. At several points along its length is secured a flexible strip of same metal as tube or of one having the same coëfficient of expansion. The bent tube may be considered as a series of Bourdon springs placed end to end. If the bends are of equal radii of curvature, an internal pressure would produce a tendency to straighten each, or collectively to elongate the whole. This elongation is restrained and converted into a magnified lateral motion by means of the flexible strip. If the bends on one side of the tube are of greater radius than those on the other, the motion due an internal pressure will be the resultant of an elongation and a lateral deflection, the lateral deflection being due to the difference in the sums of the forces tending to straighten the bends on the opposite sides of the tube. When the flexible strip is applied to the side of the tube with the larger bends restraining the component of elongation, an increased side deflection is produced.

By mounting such a tube with a marking point attached in connection with a uniformly moving chart, an extremely simple and reliable recording pressure indicator may be devised.

The sensitiveness of the tube may be varied by changing proportions and making different combinations of cross sections, thickness of walls, radii of curvature of bends, number of bends, and length of tube. The same form of instrument is adapted for use as vacuum as well as for pressure indicators.

A NEW INDICATING OR SELF-REGISTERING THERMOMETER (EXPERIMENTAL MODEL). By Prof. W. H. BRISTOL, Stevens Institute, Hoboken, N. J. [ABSTRACT.]

THE pressure indicator described in the preceding paper is filled with an expansible liquid, as alcohol, and permanently sealed.

Variations in temperature produce expansion of inclosed liquid causing internal pressure, which in turn gives deflections corresponding.

With marking point and chart for recording deflections, a simple selfregistering thermometer may be constructed.

A NEW INDICATING OR SELF-REGISTERING BAROMETER (EXPERIMENTAL MODEL). By Prof. W. H. BRISTOL, Stevens Institute, Hoboken, N. J. [ABSTRACT.]

THIS instrument is an application of the pressure indicator already described. A tube, made by electric deposition, is exhausted of air and sealed. The walls of the tube being sufficiently light, it is sensitive to small changes of external pressure: as, for instance, atmospheric changes.

For a self-registering instrument it would only be necessary to mount such a tube, with its marking point, in conjunction with a moving chart for receiving the record.

BEST METHODS OF MAKING INSTANTANEOUS PHOTOGRAPHS DURING BOTH DAY AND NIGHT. ILLUSTRATED BY EXPERIMENTS AND PROJECTIONS. By Dr. E. P. HOWLAND, Washington, D. C.

[ABSTRACT 1]

INSTANTANEOUS photography by the discovery and introduction of dry plates has given a great impetus to science in every department. It is now necessary that investigators in most branches of science should have a practical knowledge of the art. It records his discoveries by a process of Nature's engraving that is absolute truth. Any advancement in this art by discovery or application interests all investigators. In a condensed form, I will state some of the most important facts in relation to this subject and exhibit specimens of actual results.

The best lens for taking instantaneous photographs of landscapes and moving objects at a distance of one hundred feet and over is a single achromatic lens with the largest diaphragm that will give good definition, a single achromatic obstructing less light than a double achromatic lens with the same sized diaphragm and equal focus. As a single achromatic

cannot be used for near objects, on account of distortion of the image, a double achromatic lens is absolutely necessary with the largest diaphragm that gives good definition. Magnesium in powder with any substance that will cause a rapid combustion is the best substance known for producing a light for instantaneous photography in dark rooms or at night. Chlorate of potash, sulphur, guncotton, sulphide of antimony, picric acid and other substances can be used with the magnesium; but I prefer magnesium with one-third its weight of flour of sulphur. This has given me satisfaction, is a safe compound to use and can be ignited by any burning substance or the electric spark. With the camera six feet from the ob ject and the flash light two feet back and a little to one side of the camera, thirty grains of magnesium and ten grains of sulphur with a reflector behind the flash, will give a good photograph on an ordinary plate of No. 25 1 This paper was accompanied by an exhibition on the screen of the photographs alluded to.

sensitometer or an orthochromatic plate No. 27. At twelve feet distant, one hundred twenty grains of magnesium and forty grains of sulphur are required. Good photographs can be taken on a 25 sensitometer plate at the distance of twenty-four feet by flashing four hundred and eighty grains of magnesium and one hundred and sixty grains of sulphur. On a 35 sensitometer plate one-half of this quantity is sufficient.

At a distance of six feet, this flash light, I find, is equal in its actinic effects on the plate to the ordinary ribbon magnesium lamp running thirty seconds, with a ribbon one-eighth of an inch in width and burning twelve inches of ribbon.

At twelve feet distance of camera, the flash light is equal to the exposure with magnesium lamp of two minutes and burning four feet of ribbon. At greater distances than twelve feet my experiments of comparison are indefinite. If a white screen is placed on one side of the object, opposite the side on which the flash is made and a white screen or mirror behind the flash, the illumination is improved and the shadow is less dense. The same result can be obtained by having on the other side of the camera fifteen grains of magnesium with five grains of sulphur and igniting them both at the same time by a spark from a small Ruhmkorff coil. An intervening screen of translucent cloth or paper or ground glass between the the flash and object, will also give fine results but more magnesium is required to be burned as some of the light is obstructed. Exposures by day, when the time is less than one-tenth of a second, should be made from 11 A. M. to 2 P. M. in clear sunshine. The sensitive plate used for instantaneous work should not be less than 25 sensitometer and fewer failures will be made with number 30 or 35. One of the photographs that I will show you is a street view and U. S. Custom House in Charleston, that I took after the earthquake at 12 M., on Sept. 16, 1886, on a 25 sensitometer plate with a single achromatic lens and diaphragm, clear sunshine, estimated time of a second, using a metal drop shutter. Another photograph is a street scene in Washington, corner 44 Street and Pennsylvania Ave., taken at 1 P. M., July 10, 1887, on a 35 sensitometer plate with a double achrof matic lens, diaphragm, clear sunshine, time of a second, using a Prosch shutter. The moving objects in this photograph appear as if at rest in the attitudes seen. Another photograph is one that I took of a snow scene in Washington, corner of 7th and Pennsylvania avenue, at 11 A. M. April 1, 1887, on a 25 sensitometer plate, with single achromatic lens and diaphragm; thin clouds and snowing slightly, estimated time of a second, using a drop shutter with rubber band accelerator.

The shorter the time in which a photograph of moving objects is taken when a good impression can be obtained on a plate the more perfect the photograph. Professor Maybridge has taken photographs of moving objects in the part of a second.

Distance and velocity of moving objects must be taken into account in successful instantaneous photography. With a lens of five-inch focus and object 1,000 feet distant moving at ten miles per hour, the image on the sensitive plate will change 13 of an inch in one second. A railroad train, moving at

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the rate of forty miles an hour, at the distance of four hundred feet, or a man walking two and one-half miles per hour, at twenty-five feet distant, will change the image on the plate the same amount in the same time. The change of over one-half an inch in the image will make a mixed blur of objects, but if the time is reduced to the of a second, the image will then only change the .0036 of an inch, and this change of less than the .0004 of an inch will give a distinct image. The actual motion of a railroad train at forty miles per hour is fifty-eight feet and eight inches per second. A street car at ten miles per hour is fourteen feet and eight inches and a man walking at the rate of two and one-half miles per hour is three feet and eight inches per second.

The method of calculating the change of image on the plate is the same as the lever; the long arm being the distance from the moving object to the lens and the short arm the focus of the lens.

The photograph of a lightning flash can be taken at night by adjusting the camera for distant objects by daylight and then at night pointing the camera with the cap off toward the thunder cloud and await the flash. A single achromatic lens is the best to use. A good photograph of a lightning flash that I will show you was taken by Prof. C. F. Marvin of the U. S. Signal Office, June 19, 1887, at 3 A. M., taken on a Carbutt plate, No. 24 sensitometer, with double achromatic lens, 10-inch focus, diaphragm. The camera was left open four minutes during which time several successive perpendicular and horizontal flashes were photographed on the plate. The exposure was made in Washington, corner of 13th and S streets, N. W. The building photographed on the plate by the lightning flash is Howard University. Good photographs can be taken of the sparks from an induction machine having quart jars in connection with the prime conductors and using a short focus lens.

The photographs exhibited in rapid succession were taken by myself with a 5-inch focus lens and diaphragm on a 35-sensitometer plate.

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One photograph sent me from the U. S. training school at Willett's Point, New York harbor, is that of a mule with his head blown off with a dynamite cartridge and photographed before falling to the earth. Taken with a 16-inch focus lens, diaphragm, on an Eastman plate, sensitometer 22, 2 P. M., sunshine and light clouds. Another photograph taken by Prof. C. W. Smiley of the National Museum, Washington, is a mackerel schooner under full sail, taken from the deck of a steamer going in the opposite direction. Lens 16-inch focus, diaphragm, exposure ʊ of a second, plate sensitometer 25, sunshine, 12 M. A photograph of base ball playing, showing balls in the air, was taken by Mr. C. C. Jones, assistant photographer U. S. surveys, with a detective camera of 6-inch focus, diaphragm at 4.30 P. M., July 15, time of a second, plate sensitometer 26. The sensitive plates used in instantaneous photography, particularly the special orthochromatic, must be changed and developed in the least possible amount of actinic light or the negatives will not be clear and distinct. The record I have given of the practical experience in instantaneous photography may be of service to many in their scientific investigations.

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