is lighted by five windows. Eight flights of spiral stairways furnish access to the watch room, the first seven of which make half a revolution of a spiral, but the eighth a whole revolution. This arrangement does away with the incumbrance of a central shaft to support a winding stairway, and allows of a better lighted interior and of more room. The structure is 150 feet high from base to focal plane, and 165 feet above the level of the sea; shows a first-order light, and cost about $100,000. The spiral stripes shown in the cut are added to distinguish it, as a day-mark, from adjacent sea-lights.

Many brick lighthouses of this type have been built, among which are those at Cape Hatteras, Currituck Beach, and Body's Island, North Carolina; Morris Island, South Carolina; Sand Island, Alabama; Cape Foulweather, Point Arena, and Pigeon Point, on the Pacific coast.

Minot's Ledge lighthouse was almost the first, if not the first, important structure erected by the Lighthouse Board. According to General Barnard, himself an engineer of wide fame, "it ranks, by the engineering difficulties surrounding its erection, and by the skill and science shown in the details of its construction, among the chief of the great searock lighthouses of the world." [For an account of its erection, see Appletons' "Cyclopædia," article LIGHTHOUSE.] The board gave to the plan and its execution its freshest and best powers, and the combined energies of all its members. A careful survey of the rock was made by Major Ogden, of the Topographical Engineers, and then, after a full consideration of all the difficulties by the full board, the preparation of the plan was devolved on the chairman of its committee on engineering, General Totten, then Chief of the Engineers of the army, who planned the masonry tower for this difficult position, and so successfully that, with the exception of the lower stones of the foundation, which had to be studied out of the rock itself, and some details of the construction, the tower was built throughout by B. S. Alexander, then Lieutenant of Engineers, according to the plans of General Totten. The brief memoir left by Colonel Alexander, the only authentic record of the construction of the tower, brief and modest as it is, shows that the skill and ability of the builder equaled that of the designer, and the great tower stands as a monument to both and to the board that availed itself of their powers. The last stone was laid June 29, 1860, five years from the commencement, and the cost, including the keepers' houses on shore, was about $300,000. Spectacle Reef lighthouse, a similar structure, stands on a limestone reef at the northern end of Lake Huron, near the Straits of Mackinaw, which join it to Lake Michigan. The nearest land is ten and one half miles distant, but it is sixteen miles from Scammon's Harbor, where the work for it was prepared. The waves have

a fetch of one hundred and seventy miles to the southeastward, but the ice-fields, which are here moved by a current, and which are thousands of acres in area, and are often two feet thick, had to be specially provided against, as, when moving in mass, they have a force which is almost irresistible. But this is overcome by interposing a structure against which the ice is crushed, and then its motion is so impeded that it grounds on the shoal, on which there is but seven feet of water, and forms a barrier against other ice-fields. The tower (see cut) is in shape the frustum of a cone, thirtytwo feet in diameter at the base, and eighteen feet at the spring of the cornice, eighty feet above the base. The cornice is six and the parapet seven feet high. The focal plane is four feet three inches above the top of the parapet. The entire height of the masonry above the base is ninety-three feet, and of the focal plane ninety-seven feet three inches; the base is eleven feet below, and the focal plane eighty-six feet three inches above the water. For the first thirty-four feet, the tower is solid; from thence it is hollow, and in it are five rooms one above the other, each fourteen feet in diameter, with different heights, from nine feet two inches to seven feet eight inches. The walls of the hollow portion are five feet six inches at the bottom, and taper to eighteen inches at the spring of the cornice. The interior is lined with a four-inch brick wall, between which and the masonry is a two-inch air space.

The blocks of stone below the cornice are all two feet thick; those of the solid portion of the tower were cut to form a lock on each other in each course, and the courses are fastened together with wrought-iron bolts two and a half inches thick and two feet long, while the lower course is bolted to the foundation-rock with bolts three feet long, which enter the bedrock twenty-one inches, the other courses receiving the bolts for nine inches. Each bolt is wedged at both ends, and the bolt-holes, which were made with the diamond drill after the stones were in place, are plugged with pure Portland cement which is now as hard as the stone itself. Hence the tower is in effect a monolith. The stones were cut, as were those of Minot's Ledge, at the depot, and fitted, course by course, on a platform of masonry, and the work was so well done there that a course could be, under favorable circumstances, set, drilled, and bolted in three days. The main difficulty, however, lay, as in Minot's Ledge tower, in the preparation of the foundation. This was overcome by a pier of protection inclosing a coffer dam. The pier was a cribwork of twelve-inch timbers built upon ways at the depot, as a ship might have been, when it was launched, and towed by a number of steam. ers to the reef and grounded on its site. It was of wood, ninety-two feet square and twentyfour feet high, having an inside space fortyeight feet square, and was divided into compart

ments, which were ballasted to make it firm. Thus a protected pond was formed for the coffer-dam, designed by General W. F. Raynolds, of the United States Engineers, and a landing wharf was afforded for material, as well as for the reception of quarters for the men, all twelve feet above water, and out of reach of ordinary waves. The coffer-dam was thirty-six feet across, and cylindrical in form. It was made of jointed staves fourteen feet long, four inches thick, and six inches wide, held in place by three iron hoops, like a tub, and braced and stayed inside against a center post, the axis of which coincided with the axis

SPECTACLE REEF LIGHTHOUSE, LAKE HURON.

of the cylindrical coffer. It was built at the surface of the water, and suspended exactly over the site of the tower. A loosely twisted inch and a half rope of oakum was tacked to the lower end of the staves, and then the cylinder was lowered to the bed-rock, which had such irregularities on its surface that some of them were three feet high. All these were compensated by driving the jointed staves home with a heavy top-maul, the oakum rope serving as calking; and this was made approximatively water-tight by an ingenious arrangement of a loosely twisted four-inch hay-rope and a canvas flap, which was attached in part to the outside of the lower edge of the cylinder, that lay in part flat on the rock, and which was forced into the angle by the outside pressure when the pumps commenced lowering the water in the dam. The work was commenced

in May, 1870, and the light was first exhibited from the finished structure in June, 1874; but the available working time spent on this lighthouse was but about twenty months. This tower, which cost, including the steamer and appliances of all kinds, about $375,000, is our best specimen of monolithic stone masonry. It was built by General O. M. Poe, of the United States Engineers, who was General Sherman's chief engineer in his march to the sea. Its strength has been thoroughly tested by the ice push already. When the keepers returned to the tower on May 15, 1874, they found the ice piled against it to a height of thirty feet, which is seven feet higher than the doorway, and they could not effect an entrance to the tower until they had cut through the iceberg, of which this lighthouse formed the core. The cut shows this lighthouse surrounded by an ice-floe.

The board is now building a stone tower in Lake Superior, on Stannard's Rock, twentyeight miles from shore, for which the steamer and the plant used in erecting the light on Spectacle Reef are being used. It will be, when finished, 1013 feet in height, will cost about $300,000, and will show a light of the second order.

Tillamook (Oregon) lighthouse is placed on an isolated basalt rock high out of water, about one mile from the mainland, in fifteen fathoms of water, and about twenty miles south of the mouth of Columbia River. It is divided above low water into two unequal parts by a wide fissure, with vertical sides running east and west, standing one hundred feet above the sea, with a crest capable of such reduction as to accommodate a structure not larger than fifty feet square. A landing could with difficulty be made on the side next the shore during a smooth sea. The rugged character of the headland, the tendency of the sea face to landslides, and the great distance from Astoria, the nearest supply-point, made the execution of the work a task of labor, difficulty, danger, and expense. The drowning of the foreman on the landing of the first working-party tended to confirm the prejudices of the local public against the enterprise, and to increase the difficulty of obtaining the services of skilled workmen. On October 21, 1879, however, four workmen, with hammers, drills, bolts, provisions, fuel, a stove, and some canvas to protect them and their supplies from the weather, were landed, and, a few days later, five more men and a small derrick were got to the rock, from which time the commencement of the work may be dated. For the first nine days after reaching the rock, the nine quarrymen had no shelter from the rain and spray, except that of the canvas lashed to ringbolts. But during this time they cut a shallow niche in the north and east sides, in which they set up a strong timber shanty, which they bolted to the rock, covered with canvas, and secured to ringbolts. From this they secured safety, but got little comfort. After setting up the

main derrick and cutting a pathway up the face of the rock, they opened a bench around it by suspending the workmen on staging supported by bolts let into the rock's crest. The bench once formed, the reduction was pushed to the center. The outer surface of the rock was easily removed with moderate charges of black powder, but the nucleus was hard and firm, and giant-powder was necessary to open the mass, when large charges of black powder acted satisfactorily. The working party, in spite of their rude, uncomfortable quarters, worked diligently through the winter with good results. But the work was much delayed by spells of weather so bad that little could be done. The coast was visited by a tornado in January, which caused the waves, reflected from the rock, to be carried by the wind over its crest, so that for many days continuously the receding floods poured over the eastern slope, making work impossible. On one such day this cataract carried away the supplyhouse, and even endangered the quarters of the working-party. For more than two weeks at this time it was impossible for the steamtender which supplied their wants to cross the

bar at the mouth of the Columbia River to go to their assistance; when, after sixteen days, communication was reopened, the party was found to be safe, but much in want of fresh provisions. These were supplied by an endless line running between the mast of the supplyvessel and a ringbolt driven into the top of the rock, in water-tight casks suspended by slings from a traveler, which was made to move along the line.

In May the top of the rock was leveled, and a foundation made about eighty-eight feet above the sea, and, on the 31st, three masons, four derricks, a small engine, and the appliances for laying the masonry, were landed. The stone, a fine-grained, compact basalt, quarried near Portland, and cut to dimensions by contract, was delivered at Astoria and shipped to the rock on the tender. The first cargo was landed on June 17th; on the 22d the cornerstone was laid, and then the rest of the material was shipped to the rock as the weather permitted.

The building is a square, one-story keeper's dwelling, with a rectangular extension for the duplicate siren fog-signal apparatus. From the

local foreman had a bonfire built on the rock as soon as possible, but the vessel was lost probably before the signal could be seen. It was on this night that the working-party lost their supply-house, and came so near losing their quarters, if not their lives.

The illuminating apparatus used by the lighthouse establishment varied with the dates of its use. The beacon on Point Allerton, Massachusetts, was illumined in 1673 by "fier balls of pitch and ocum," burned in open braziers. The lighthouse on Little Brewster Island, Boston Harbor, erected in 1715-'16, was first lighted by tallow candles. Then followed the spider lamp, burned in the lantern as it might have been in a window. In 1812 the Government bought of Mr. Winslow Lewis, for $20,000, the patent for his "magnifying and reflecting lantern." This is described as consisting of a lamp, a reflector, and what was called the magnifier. The reflector was of a thin sheet of copper, commonly segments of a sphere, plated over with a slight film of silver, though the copper was so thin that its compression between the arms of its iron supports materially altered its form, and its silvered concave surface had much the grain and luster of tin ware, and would reflect no distinct image. The patentee, in 1812, made no pretension to a knowledge of optics as now understood, and his reflectors came about as near to a true paraboloid as did a barber's basin. The lamp, roughly constructed on the principle of Argand's fountain-lamp, burning from thirty to forty gallons of oil per year, had a three-quarter inch burner, and was attached to a circular iron frame in front of the reflector. Before the lamp was a so-called lens, of bottle-green glass, shaped like the bull's-eye let into a ship's deck, from two and a half to four inches thick through the axis and nine inches in diameter, which was supposed to have some magnifying power. This apparatus was inclosed in a massive wrought-iron lantern, glazed with panes ten by twelve inches in size. The effect of the whole was characterized by one of the reporting inspectors as making a bad light worse. But its main merit seems to have been that of economy, as the patentee, who had fitted thirtyfour lighthouses with his apparatus, contracted in 1816 to maintain the lights on receiving one half the oil previously consumed, and again, in 1821, for one third of the old allowance.

This apparatus is spoken of more respectfully in a report to the House of Representatives in 1842, made by its committee on commerce, from which it appears that "the improvement in the character of the light and the economy in saving oil were subjects of high commendation by the Government." It also appears that the use of the magnifying bull's-eye was gradually abandoned, so that but few remained in 1838, and the last one was removed in 1840. The administration of the system was largely improved. The reflectors were made on true optical principles, approximating,

if not reaching, the paraboloid in form, and were heavily silvered and properly placed. The heavy lantern frames were replaced by lighter ones, the small panes of glass by larger ones, and the ventilation of the towers was so largely improved that obscuration by smoke was no longer unpreventable. The system, largely improved, was retained, but its administration was good only where it had faithful, intelligent, and honest administrators. Finally, the reflectors were so well made and so well placed that, in certain instances, it is now a question whether a better light was possible than was then furnished. Some of the old reflectors then used appear from recent examination to have an enormous candle-power. But a poor light was the rule, and a good light the exception. War was made on the system of reflectors, and, when the lighthouse establishment was turned over to the Lighthouse Board in 1852, the reflectors were replaced by the Fresnel lenticular apparatus, found so successful in France, and more or less throughout the world. The adoption in this country of the lenticular apparatus made it possible for a light-keeper of average capacity to keep a good light, and impossible for him to keep a bad one, except by violation of plain rules and avoidance of routine duties. Besides this, the saving in oil effected by use of the lenses over reflectors was so great that the expense of exchanging the one for the other was saved in a few years, although the first cost of the lenses was quite large.

It was shown, in a report made to Congress in 1858, that the mean average cost of each lighthouse, for the five and a quarter years preceding the organization of the Lighthouse Board, was $1,302, with oil at an average of $1.13 per gallon, while, for the same period after the board took charge, it was but $1,286, with oil at $1.62 per gallon. Thus it appeared that under the board the average cost of maintaining each light was about $16 per year less than under the previous management, although oil was about fifty cents per gallon more; and it was broadly claimed by the board, and the claim does not appear to have been disputed, that by the change it furnished under the new system, "at least four times as much light for the benefit of the navigator as the best system of reflector lights which has been devised, and at the same time at a consumption of not more than one fourth of the quantity of oil, required for the best system of reflector lights."

A full description is given in Appletons' "Cyclopædia" of the reflectors, under the head LIGHTHOUSES, and of the lenticular apparatus under the name of AUGUSTIN FRESNEL, its inventor.

The illuminant of the lighthouse establishment has been changed whenever a better one has been found. The "fier-balls of pitch and ocum," used in the open brazier at Point Allerton in 1673, were succeeded by tallow candles at Little Brewster Island in 1716, which gave