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between high and low tide levels. A characteristic of the Limnoria is that it thrives in polluted water of high salinity.

Sphaeroma pentodon Richardson (Crustacea Group):

This borer has the same general appearance as the Limnoria, but is much larger, thus bearing a similar relation to the latter, as the Xylotrya does to the Teredo. Its width is about 4 inch, and its length about 1⁄2 inch. The color varies from dark olive to reddish brown. Its smooth, sliding back armor "scales" can easily be seen, and when disturbed it can roll itself into a ball about 4 inch in diameter. Its burrow is about 2 inch in diameter and usually remains near the pile surface, following the softer portions of the wood. This burrow being near the surface is quickly attacked by the Limnoria, and hence often obscured by being eaten away irregularly. The range of attack is usually between high and low water, and the borer thrives in all conditions of salt water, brackish, polluted, or of clear, high salinity.

From the foregoing it can be seen that the destruction of an unprotected timber pile can be complete if the borers enter the locality. Teredo will general honeycomb the outer three inches between mud-line and low water. Xylotrya will reduce the center section between mud-line and low water; Limnoria will eat off the pile between high and low tides, and Sphaeroma will burrow into the surface shell between high and low tides. Piles in brackish water can be destroyed by Teredo and Sphaeroma; in polluted water by Limnoria and Sphaeroma, and in clear water, at high salinity by all four types.

The foregoing also shows that the critical stage of marine borer growth for which all piles must be prepared is the larval condition. If the larvae can be repelled because of finding no untreated wood, or no irregularities or crevices in the surface, long life of the piles may be expected.

The following tabulation of Pacific Coast harbors gives the names of marine borers already discovered, and a statement of the length of life of creosoted fir piling. "Teredo" have commonly been reported at points where it is practically certain none exist, but rather Xylotraya of the teredo family. It is also probable that Sphaeroma exist at all these points but were not reported because of difficulty of inspection or failure to recognize them. The minimum life of creosoted piling roughly indicates the severity of attack, if treatment is imperfect or if a blemish is present allowing borers to secure a hold. The maximum life indicates the possibilities of the better quality of such piles. Untreated piling has not been listed because its life is negligible at these points, except t Tillamook, Yaquina and Coos Bays, where borer attack is light and probably sporadic. It is of interest to note that the Teredodiegensis was given its name by Bartsch because of having been found in San Diego Bay.

ALASKA. Xylotrya have succeeded in establishing themselves in Alaskan harbors and have created much damage. They appear to thrive in the cold, fresh, unpolluted salt water of that region.

VANCOUVER ISLAND.-Limnoria and Xylotrya are present and very destructive in the harbors of Ladysmith, Nanaimo, Nanoose, and Port Alberni, and appear to be growing more active in the last few years. Untreated fir piling has been destroyed in less than a year and preserva

TABULATION SHOWING MEANS OF IDENTIFICATION OF FOUR MARINE BORERS COMMON TO THE PACIFIC COAST

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Note Where fresh water flows into salt water possibility of presence of marine borers is indicated by gathering of barnacles or common forms of molluscs on pile surface.

Pile surface indication of Teredo and Xylotrya is difficult with naked eye, but minute en trance holes may be detected with magnifying glass.

MARINE BORERS AND LIFE OF CREOSOTED FIR PILING AT VARIOUS PACIFIC COAST HARBORS

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Victoria harbor does not

tive methods have been in use for many years. suffer as severely as those mentioned above because of the volume of fresh water flowing into it. It is in this vicinity that Australian turpentine piles have been used. After 14 years of service they are reported to have completely resisted the Xylotrya, and to hav allowed only a slight Limnoria surface action.

PUGET SOUND. The extensive lumber business of the Sound, together with the innumerable timber marine wharves built of untreated or imperfectly treated piling, have permitted the Limnoria and Xylotrya to establish themselves firmly at many points around this body of water. Tide and currents coupled with the great depth of water serve to reduce the element of local pollution, and to maintain a high, clear salinity, thus providing the most favorable condition for the marine borers. The infestation seems to have grown worse in recent years, and at present untreated fir piling will be destroyed in less than a year.

TILLAMOOK AND YAQUINA BAYS.-Limnoria and Xylotrya are reported at both of these bays, but no definite data is available as to the degree of infestation.

Coos BAY.-Limnoria and Xylotrya are present in limited numbers, and their attack seems to fluctuate with lapses of comparative inactivity. The Southern Pacific Company has a structure here which contains creosoted fir and untreated cedar piling, the latter having been placed in 1912. These cedar piles consisted of sound "dead timber" cut from land which had been burned over by a forest fire. The balance were of freshly cut green timber. Recent inspection disclosed the interesting fact that the "dead timber" had been attacked, but that the green timbers were practically unaffected.

SAN FRANCISCO BAY.-This harbor has probably suffered the greatest inroads of marine borer attack of all on the Pacific Coast, and the subject has already been given widespread publicity in engineering publications.

Shipping activity and the harbor's peculiar geographical configuration have allowed the borers to become well established. San Francisco Bay and the adjoining San Pablo Bay have a total length of about 80 miles, with an average width of about 10 miles. The only inlet from the sea to this great body of water is through the narrow gate, and the result is that a tremendous current is created at the ebb tide. This current rushes by the whole San Francisco waterfront, thus causing extreme borer action, except where sewers pollute the water.

The water of the San Joaquin and Sacramento Rivers was formerly of sufficient volume to hold back the salt water from San Pablo Bay, and to prevent it from entering Carquinez Straits, but extensive agricultural development of the Sacramento Valley, including rice culture, and the years of slight rainfall, have served to reduce the amount of fresh water reaching the Straits. As a result, the water from the juncture of San Pablo Bay and the Straits, through Suisun Bay to the point where the above-mentioned rivers meet, a distance of about 25 miles, has become brackish. A great number of industrial wharves had been built within these limits, using untreated piling, and the resulting destruction from Teredo navalis and Sphaeroma has already run in millions of dollars. The activity of both borers give practically no surface indications, and the imminent danger was not realized until wharves and warehouses collapsed.

The condition of borer infestation on the east side of San Francisco Bay has been disclosed by investigation which attended the removal of the Old Long Wharf of the Southern Pacific Company in 1919. This wharf,

originally completed about 1871, consisted of five docks, A, B, C, D, and E, radiating from the approach pier, somewhat as the fingers of a hand, and was first built of untreated fir piling. By 1889 the borer action had become so severe that it was decided to re-drive the docks with creosote piles. This was carried out between the years 1890 to 1901, there being driven an estimated total of about 14,000 creosoted piles, a few of which had been treated at the Southern Pacific Company's temporary plant at San Pedro, and the balance at their permanent plant at Oakland.

Changes in the Oakland City waterfront necessitated the removal of the above wharf in 1919, and when this was done, a majority of the creosote piles were found to be sound and unaffected by marine borers. Replacements in the intervening period had been too small in number to be appreciable. The following tabulation reflects the results of inspection of the piling:

Creosoted Piles in Dock A, Driven in 1890 :

Removal of piling completed before inspection was inaugurated: Thirty-three creosoted piles showed following condition:

Sound, fit to redrive....

Slightly attacked between low and high water.

Severely attacked, between low and high water.

Completely destroyed, between low and high water..

Total number examined

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Creosoted Piles in Dock B, driven in 1898:

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Severely attacked, between low and high water.
Completely destroyed, between low and high water. 116

74

14.15

22.18

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Severely attacked between low and high water.
Completely destroyed, between low and high water.

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Severely attacked, between low and high water.
Completely destroyed, between low and high water. 345

240

9.66

13.88

Total number inspected...

SUMMARY-Docks C, D and E.

2,485

100

Per cent.

In sound condition, fit to redrive..
Severely attacked, between low and high water.
Completely destroyed, between low and high water. 560

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All the sound piles were redriven elsewhere. There is no reason for believing that the Summary of Docks C, D and E would have been greatly affected had it been possible to include piles from Docks A and B. Hence it is likely that 75 per cent. of the original creosoted piles are still in service. Attention is also called to the fact that many of those slightly attacked were redriven inshore, with the result that about 80 per cent. of the original total are still serving.

Investigations of the Dumbarton Cut-Off trestle of the Southern Pacific Company, at the extreme south end of the Bay, have disclosed the presence of Xylotrya, Teredo navalis, Limnoria and Sphaeroma.

Teredo diegensis has been found at only one point in the Bay, at the Schaw-Batcher ship yards, near South San Francisco, on the West side.

The foregoing briefly outlines the manner in which San Francisco Bay has become infested with five forms of marine borers, with conditions such that they can thrive and work severe damage. The brackish water at the north in Carquinez Straits and Saisun Bay is infested with Teredo navalis and Sphaeroma, and the water of San Francisco Bay proper, with high salinity, is infested by both of the above, together with Xylotrya, Limnoria and Teredo diegensis.

SAN PEDRO AND SAN DIEGO BAYS.-Both of these harbors have suffered attacks of Xylotrya and Limnoria, with Teredo diegensis present in a minor degree. Test piles were driven at both places, including untreated piles, old creosoted piles from Long Wharf, and freshly creosoted piles. Those untreated have already been severely attacked by Limnoria, and one of the Long Wharf piles at San Pedro shows slight evidence of borer action.

TESTS. The following list shows special service tests now being observed by the Sub-Committee:

1. Four sets of 7 piles each driven as follows:

March, 1920, Northern Pacific Ry. Co....
September, 1919, Northwestern Pac. R. R. Co..
September, 1919, Southern Pacific Company.
June, 1920, Santa Fe Railway Company.

Seattle .Tiburon San Pedro

San Diego

Each set includes 1 untreated fir pile, 2 freshly creosoted fir piles, and

4 creosoted fir piles taken from Old Long Wharf in 1919.

2. Twelve creosoted Douglas fir piles from Old Long Wharf, driven as brace piles in Southern Pacific Company Wharf No. 2-Oakland Pier, October, 1919.

3. Sixteen eucalyptus piles driven in dolphins of Alameda Ferry Slip of Southern Pacific Company, 1921.

4. Sixteen eucalyptus piles driven in dolphins of Oakland Auto Ferry Slip of Southern Pacific Company, 1921.

5. Eighteen dolphin piles in Georgia Street Wharf, South Vallejo, of Southern Pacific Company covered to above high water with "Moran" paint, 1921.

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