red oil-cloth, on which were placed the smaller articles and models. space, 18 feet by 35 feet, was railed off in which were placed the lenses, lamps, instruments, and delicate models. On the side wall of the section hung a large map, showing the location of every light under the jurisdiction of the Light-House Board. On the rear wall of the section the pictures were arranged. The space outside the building consisted of a large platform on which was placed a light-house, fog-bell, and buoys of different classes. Alongside the platform was placed a house containing both the caloric and steam sirens.

The exhibit within the building was ready by the opening day. On July 1st the fog-horns were working, and on July 4 the light-house was lighted for the first time.

The steam siren was, at the request of the authorities used to give notice of the daily opening, and closing of the Exhibition.

The exhibition was classified as follows:

Lenticular apparatus.

Lamps.

Lamp-burners.

Wicks and chimneys.

Illuminating materials.

Cleaning materials, and implements.

Testing instruments.

Light-houses, and models.

Buoys.

Fog-signals.

Light-ships.

Maps, plans, and graphic representations.

LENTICULAR APPARATUS.

The apparatus employed in the light-houses of the United States is almost exclusively of the catadioptric or Fresnel system. They are divided into seven orders, according to their size and the intensities of their lights. They are also distinguished according to the appearances they present as follows: Fixed white; flashing white; fixed varied by white flashes; fixed red; flashing red; flashing red and white; fixed white varied by red and white flashes; fixed white varied by red flashes; fixed red varied by red flashes.

Lights of the first order, being visible at the greatest distance, are placed upon the headlands or points farthest to seaward. The smaller and colored lights are used in narrow seas, passages, rivers and channels, or to mark the entrance to a roadstead or port, and in less important places.

The exhibit of lenticular apparatus was as follows:

First-order lens, white, flashing every 10 seconds.—Illuminates, 360° of the horizon; lamp and attachments complete for lard oil.

Third-order lens, fixed white.-Illuminates 360° of the horizon; lamp and attachments complete for lard oil.

Fourth-order lens, white, flashing every 10 seconds.-Illuminates 360° of the horizon; lamp and attachments complete for mineral oil.

Fifth-order lens, fixed white.-Illuminates 300° of the horizon, with catadioptric reflector; lamps and attachments complete for mineral oil. River or stake lights.—In use on the Western rivers. These lights are placed on stakes or posts about 10 feet high, which can be moved as the channel changes. One of these lights was fitted up as in service and placed near the light-house; the other was among the exhibit of lenses. These lights can be plainly seen from 6 to 7 miles. The cost of posts is nominal, as they are cut where they are used. The cost of the entire outfit does not exceed $10, and the cost of oil and wick used in a lamp, per night, does not exceed 2 cents. Mineral oil is used, and from one-third to one-half pint is consumed each night. If properly trimmed, the light should burn 16 hours without retrimming. The lantern is so constructed that the wind cannot blow the light out nor even make it smoke. To secure this result each lantern is tested in front of a steam blower before it is accepted.

Range or leading lights.-These lights are used when it is necessary to keep in a channel, or mark where a channel changes its direction. Both lights must show in one vertical plane. If more than one set is used, the new range will mark the change in the channel, and before the old one is off the new one should be on.

Running lights.-For steamers at night, as used on board the United States light-house tenders and supply vessels.

Mast-head lights.-For the banks of a canal, showing the light up and down the canal.

Fourth-order lens.-Shows a red and white flash alternately every 10 seconds, illuminating 360° of the horizon. In use on the light-house outside of the Government building.

LAMPS.

Three kinds of lamps are in use, the mechanical, the moderator, and the hydraulic.

In the mechanical lamp the oil is forced into the burner by pumps driven by clock-work, run by a weight. In moderator lamps the ascent of the oil is effected by a weighted piston. Hydraulic lamps depend for their supply upon the pressure of the oil above, regulated by various devices.

A complete exhibit was made of the different lamps, of which the following is a list:

Wagner's mechanical lamp, 1855.-A reciprocating motion is given to two vertical shafts which pass through the oil cistern and work the feed pumps. A fly regulates the velocity. The flow of oil is regulated

The pumps

by turning a screw placed in the upper part of the oil case. communicate with the reservoir of oil by means of a feed-pipe fitted at its lowest extremity with a small strainer. The pistons are formed of plungers of calf-skin, and the valves are of the same leather.

Lepaute's mechanical lamp, 1855.—The mechanism in this case consists of a barrel carrying a crown-wheel, fitted on its two faces with friction rollers, which make an escapement with four bent levers. These levers work two shafts, which traverse the oil cistern and put the four feed-pumps in motion. The flow of oil is regulated by a small orifice in a diaphragm placed in the upper part of the pump case. A small pointed screw penetrates the orifice and the flow is regulated at will by turning the screw.

Moderator lamp, 1855.-A cast-iron piston, bound with leather, and of such a size as to gently slide in the lamp-cistern is connected above with a horizontal shaft by a chain which winds around the shaft. On the piston are weights to make it descend. By turning the shaft the chain is wound up and the piston ascends; then left alone it causes by its pressure a flow of oil to the burner. The regulator is a small orifice through which the oil is forced and a needle is pushed in or withdrawn to diminish or increase the supply. This device is usually arranged so as to be self-acting.

Coate's valve lamp, 1856, fourth order.-The reservoir of the lamp is a hollow cylinder and is placed above the lens, on the framework of which it rests. The flow of oil is regulated by an automatic valve to the axis of which a stem is attached bearing at one extremity a counterpoise and at the other a cup into which the surplus oil from the burner drips. This cup is pierced with a little hole, and when full of oil sustains its counterpoise; but if the oil ceases to flow, the counterpoise falls and opens the valve.

Meade's lamp, 1857, third order. This also has a reservoir in the dome of the lantern. By means of a screw-pin on the supply tube, the tube can be closed or opened at will, thus regulating the delivery of the oil. Funck's hydraulic float lamp, 1876, first order.-The reservoir is placed as in the two preceding lamps, above the apparatus. The flow is regulated by a small float carrying a valve, and contained in a close chamber. When the supply is too copious, the float rises and the valve stops the orifice of the supply tube. As the oil in the chamber is consumed the float falls and allows a freer flow of oil. The relative distance of the valve from the float is regulated by means of a thread cut on the valve stem. The lamp is in general use in the light-houses of the United States.

Funck's hydraulic float lamp, second order.-Its action is the same as that of the last-mentioned lamp, but it has a glass float chamber showing the float and the action of the float. One of these lamps fitted for service was also exhibited.

Third order Funck's hydraulic float lamp.

Fourth order float lamp for mineral oil.

Fifth order lamp for mineral oil.

Fountain lamp, 1853.—An argand or constant level lamp, composed of two parts, the burner and the reservoir or fountain. The reservoir is provided at its lowest part with a valve, which lifts when the stem which is attached to it comes in contact with the bottom of the body of the lamp. A communication is thus established between the reservoir and the burner.

Common regulation hand lantern for tower use.

Lantern with lucerns. For lighting the main lamp at night, as matches are not allowed in the light-house tower.

Rod lamp.―This lamp is constructed on the same principle as the student's lamp. It is to be kept ready for use in case of accident to the main light, when but a few seconds can elapse before it is replaced by the rod lamp, which should be near the keeper on watch. It is also used while the main light is being trimmed.

Hanging lamp.-For use in the cabins of the light-house tenders and supply vessels. Its action is the same as that of Funck's hydraulic float lamp described above.

LAMP BURNERS.

The burner of a lamp is the case in which the wicks are set and lighted. Lamp-burners are provided with from one to five concentric wicks, according to the order of the light and the intensity required. The lower end of each wick is fixed to a circular carrier and raised and lowered by means of a rack. A pipe forming the stem of the burner supplies the wicks with oil.

First-order lamp burner, with a photograph of the flame of natural

size.

Second-order burner, with the same.

Third-order burner, with the same.

Fourth-order burner, with the same.

Fifth and sixth order burner, with the same.

WICKS AND CHIMNEYS.

Samples of wicks used in all the different orders of lamps were exhibited, also a case containing the different varieties of chimneys used in the Light-House Establishment.

ILLUMINATING MATERIALS.

The oil in use in the Light-House Establishment is winter-strained lard oil, which must be of such a quality that when burning in a fifthorder Franklin lamp it will give the intensity of nine candles. Samples of this oil, contained in the regulation oil-butts, were exhibited; also samples of mineral oil used in many small lights, and of signal oil, which remains fluid in any temperature.

CLEANING MATERIALS AND IMPLEMENTS.

Oil-pump.-Used to transfer oil from casks to the butts and from these to oil-carriers.

Oil-strainer. This is in two parts, the strainer proper, and the vessel to receive the strained oil. The strainer proper is a plate pierced with holes. On it is placed a piece of cloth and a thin layer of fine sand. Oil buckets and cans.-These are used to carry oil inside the lighthouse.

Measures.-These are used in determining the quantity of oil consumed in the lamps.

Service-box fitted for use.-This has a transverse handle and a cover with two lids. It is divided into three compartments. The first receives a flat tray, on which are temporarily placed greasy cloths and wick trimmings; under this tray are the clean cloths for wiping glass chimneys. The second compartment contains a triangular scraper for removing crusts of burned oil from the burner, a horse-hair brush for cleaning the lamp and tubes of the burner, and a pair of curved scissors for trimming the wicks. The third compartment contains a pair of straight scissors for cutting wicks, a measure to determine the proper lengths, and the conical mandrels for fitting the wicks on to the tubes. Dripping-pan.-A square, flat vessel with a double bottom, the upper one pierced with holes.

Lamp-filler.-For filling small lamps and lanterns.

Rouge box.-Containing polishing rouge (peroxide of iron) for polishing the glass of the lenticular apparatus and lantern.

Whiting-box.-Containing Spanish white for polishing glass and tin, and for making putty.

Lifters. For removing chimneys from lighted lamps.

Small spirit-level.-Used to verify the level of the crown of the lampburner.

Large spirit level.-Used to verify the position of the surface on which the rollers of the revolving apparatus move.

Heater for mechanical lamps.-A little lamp shut in an oblong box with two tubes.

Molds. For making plunger and valve leathers for mechanical lamps.
Punch. For cutting valves of lamps, and washers for joints.
Key. For winding revolving machinery.

Wolf's-head brush.-A long handled, round horse-hair brush, used for cleaning ceilings and staircases.

Long-handled brushes. Of horse-hair, used for sweeping rooms and stairways of the interior of light-houses.

Feather-dusters.-For dusting apparatus and glass of lanterns. Counter-brushes.-A short handled brush with long bristles for sweeping the service-table, gallery, and steps.