bor, stir up the soft bottom of Limon Bay and create currents, with the result that there is a large amount of silting in the channel through the bay. For two years in succession this silting amounted to more than two million cubic yards of material.

In order to remedy this condition, and for other reasons, it has been decided to Its construct an east breakwater also. end will be opposite the end of the west breakwater, leaving an opening of 2,000 feet. When this breakwater is completed, the silting in the channel will cease and all difficulties of transfers from one boat to another in the harbor will be eliminated. The west breakwater should be completed in the summer of 1914, and the work on the east breakwater has just commenced.

HOW THE BREAKWATERS ARE BUILT

The method of building the breakwaters is as follows:

A trestle, suitable for a double-track railroad, was driven from the shore, extending for two miles out to sea. The rock forming the bottom of the breakwater was run out on cars and dumped or plowed off until the fill was made alongside the trestle to an elevation of 15 feet below sea-level (compare page 152). Between that level and 10 feet above sea-level the breakwater was built of hard trap rock, obtained from Porto Bello, the stone ranging in weight from 1,500 pounds to 15 tons.

The stone for the armor of the breakwater, as well as all crushed stone for the Gatun locks, came from this seacoast town of Porto Bello, situated some 20 miles northeast of Colon.

This place has given all kinds of trouble. The first year we attempted to crush. stone for the Gatun locks, we had at Porto Bello a rainfall amounting to 237 inches-3 inches less than 20 feet; 9 feet of rainfall in two months; 58 inches in one month.

Everything happened at Porto Bello that could happen. Slides that no engineer would dream of occurring did occur. On an average 300,000 cubic yards of crushed stone every day were necessary for the concrete at Gatun. We had a young officer of engineers there, Captain

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Stickle, who was doing the best he could, but we were pushing him anyway; so, after he had been urged and urged and then urged again to do more, one day he sent a wireless, "Fifty-eight inches of rain this month. Anything over fifty inches considered an act of God."

THE FRENCH CANAL WOULD HAVE BEEN USELESS NOW

A little to the north of the Gatun locks the American and French canals intersect, and the picture on page 158 shows the relative sizes of the two. Had the French canal been completed it would now be out of date, for its locks would not be of a size sufficient to pass the boats that would now offer.

In the French project the sea-level part of the canal on the Atlantic side extended about 10 miles farther up the Chagres Valley than the American project. The water supply would have been materially less than in the American plan and would not have been sufficient for the substitution of locks of the size now built, and those now adopted are none too large to meet the requirements of Congress that the Panama Canal should be built of such size as reasonably to meet the demands of the future as to the size of ships.**

The canal is at sea-level from the Atlantic to Gatun; it then goes up a flight of three steps to Gatun Lake and continues at that level for 32 miles. Then down one step at Pedro Miguel to Miraflores Lake, which is 55 feet above sealevel; thence through the Miraflores locks, and the canal from there to the Pacific is at sea-level again.

The proudest day that Gatun has yet had was on the 26th day of September, 1913, when the little tugboat Gatun was lifted from sea-level to the surface of Gatun Lake, and was the first boat to pass through any lock of the Panama Canal (see page 162).

*The full length of each lock compartment is 1,000 feet. The largest ship in the world, the Vaterland, of the Hamburg-American Line, which is not yet completed, has a length of 950 feet. While it is unlikely that the huge liners used in the transatlantic passenger service will often be required to pass through the canal, still the locks are big enough to accommodate the largest ship in the world.

As soon as a boat passes the lower lock gates they are closed behind it, and water is let into that box or lock chamber from the lock above until the same level of water exists in the lower and middle locks, the boat being lifted 283 feet in this operation. After that the gate separating the lower and middle lock will be opened and the boat will pass into the second lock, the gates closed behind it, and the process repeated, the boat being lifted another 28 feet. That operation repeated once more will cause the boat to float out on the level of Gatun Lake.

The filling of the lower chamber of Gatun lock for the first time is shown in the picture on page 164. The gate on which all the men are standing is called the east gate or guard gate. These gates were completed as soon as practicable and then closed, so as to keep the sea out of the locks while dredges were completing the excavations in the lock entrance, thus not interfering with the work on the other gates nor with the machinery installation.

PAINTING MOSQUITOES

On both sides of the channel at Gatun were extensive swamps. They were great breeding places for mosquitoes, and in digging the channel through the soft, swampy bottom pipe-line dredges were used. These dredges cut up the material near the suction of the pumps, draw it in with water, and force it long distances through pipe-lines. In making the channel excavation those swamp areas were built up high enough to enable the sanitary department to drain them.

In 1912 Gatun had probably the greatest influx of malarial mosquitoes in its history; they came by the thousands. The Gatun Lake was rising at that time, and it was not known whether these mosquitoes were coming from that lake or not; so the sanitary department determined to locate all the breeding places for mosquitoes near Gatun, catch mosquitoes at each place, and after painting them turn them loose, and determine by the color of the mosquitoes caught in Gatun from what point they came.

It was found that the largest breeding

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place was off to the west of the locks, in an old swamp that had given no trouble previously. A few mosquitoes had bred in this place all the time, but there were enough wild animals in the swamp to supply food, so the mosquitoes were not forced to migrate. When salt water was pumped into the swamp water, making the mixture about 30 per cent salt, mosquitoes began to breed by the trillions.

I went down there one morning to see how the mosquitoes were caught and painted. Walking along the edge of the water, mosquito bars were seen suspended from limbs tied up at the bottom. They had thousands of mosquitoes in them ready to be sprayed with a colored liquid, and the sanitary inspector was asked how he caught them.

He said, "We have a more scientific way, but this had to be done in a hurry. We simply let the mosquito bar down, as you would over a bed, left one side of it open, and put a Jamaica negro in there for bait." As soon as the mosquito bar was full the bait was removed and the end tied up.

I saw some Jamaican negroes sitting out in front, and I said to one fellow. "John, were you the bait in that bar?" and he replied, "Yes, boss; that is the easiest money I ever earned—ten cents an hour for sitting there and doing nothing but just inviting the mosquitoes in.'

THE DREDGING FLEET

Just prior to the time that water was let into Culebra Cut, a fleet of dredges was brought up preparatory to removing Cucaracha slide, the last one that obstructed the passage across the continent. The picture on page 166 shows part of the fleet assembled for passing through the locks, and gives a good picture of a pipe-line dredge, showing the cutter in front. When this cutter is revolved, those blades loosen the dirt, the intake of the pump is just behind, and when the water is drawn in by the pump it carries in from 15 to 20 per cent of solid matter. and the pump gives it velocity enough to be carried from one-half to three-quarters of a mile through a pipe.

The entire dredging fleet is shown in the picture on page 167. There were