The city's new Cedar river dam, built at a cost of a million and a half dollars, flings its monumental gray wall across a mountain canyon, 200 feet high, a tremendous, inspiring spectacle of man's handiwork, and behind the millions of tons of concrete the impounded water is draining away steadily into the porous gravel of the north bank.

To the engineers in charge of the work there is something mysterious, almost uncanny, in the steady sinking of the flood which threatens the success of the ambitious project.

In defiance of all calculations the water has continued to disappear at an unvarying rate.

Though the water in the pond has sunk, decreasing the hydraulic pressure upon the weak north bank, it continues to go out at a rate of an inch an hour, or, roughly 4,250,000 cubic feet a day. In gallons this means a daily loss of about 318,750,000.

Stories of the pre-glacial river bed which geologists warned the city lay just behind the dam have been advanced to account for the steady drain. Most of the city engineers pooh-pooh this idea, but they have reached a stage of perplexity where they are willing to admit there might be truth in almost any explanation.

Whether or not the leak can be stopped is now the all-important question. Arrangements are being made to sluice down silt into the pond. This will cost money and take time. How much money and how much time none of the engineers will hazard a guess.

Loyal enthusiasm in the success of the city's gigantic project has been dispoiled by grave doubts. The evidence of the leaks is incontestable.

Whether or not all of the leaks from the big reservoir have been located may not be known for several weeks, perhaps even several months. The history of the streams thus far located as leaks through the glacial dyke indicate that others may be making their course slowly through the gravel formation to some more distant points of the Snoqualmie watershed. The present known leaks farthest from the dam are about two miles approximately north of the north end of the structure on the Snoqualmie side of the glacial dyke.

They were located December 10. A leak a mile and a half north of the north end of the dam appeared December 3. Another leak at Moncton, two miles northwest of the dam, appeared December 8. The largest of the streams, which, on December 7, was carrying away 26.8 cubic feet, or 211 gallons, of the impounded water every second, first appeared December 1. It is much closer to the dam.

A survey of the Snoqualmie watershed is to be begun at once to ascertain if there are other leaks still farther away. The brief history of these various streams of water pouring from the gravel mountainside at some distance below the level of the pond, behind the dam, is being perused with eager attention by the city enginbeers.

The weir readings from these streams recite the history of the astonishing leaks through the porous gravel north bank and have a definite bearing on the problem of trying to save to the city the expensive project to develop the municipal lighting plant.

The astonishing thing to the engineers is that while the weir readings have been decreasing the water continues to drop at exactly the same rate of speed. The area of the impounded water has shrunk but little so far, though its depth has decreased. Decrease in depth means decrease in water pressure on the porous soil, and that, in turn, should lighten the loss.

As an indication of how the water started to go out through the gravel wall to the north of the reservoir the conservative report of a city engineer on the ground is of interest. This tells what happened when the city first put water behind the big dam, which was during the first days of November. The numbers refer to the leaks as located on the accompanying map. This report says:

"Numbers 1, 2, 3 and 4 weirs, which have been read for three years, showed no undue increase until December 10, when numbers 1, 2 and 3 showed an increase of 50, 225 and 163 per cent, consecutively, two new springs appearing to increase the flow of Number 2.

"Number 5 weir was installed December 3, on which date there was a flow of 19.7 cubic feet per second. A maximum flow of 26.8 cubic feet per second was reached December 7, receding gradually. The present flow of this stream is estimated at three or four times its normal volume.

Number 7 stream has weir readings for part of 1911 and all of 1912. Readings taken December 8, 9 and 10 show an increase of 2.9 times the flow of 1911 and 1912 of corresponding dates and 1.2 times the maximum flow at any period. The maximum flow of this stream occurs normally in Feburary.

"From December 3 to 15 no precipitation has occurred, the weather remaining cold and dry. Frost is in evidence in many parts of the ground, indicating an increase in the above streams to be not due to local weather conditions."

The great dam itself has behaved spendidly. In two or three places on the downstream side water has seeped through in small amounts, but to a far less extent than the experienced concrete men expected.

A visit through the vast winding inspection galleries which traverse the immense structure far below the water level revealed the water in the drainage wells installed to take up any leakage pushing under the dam lower than the normal figure for a great dam. In one place in this vast gallery was the water seeping through the thick walls itself, but in a very small amount.

When the water was first raised behind the new dam the present wooden dam at the end of Cedar lake, which impounds the water now driving the lighting plant, was not disturbed. The present seepage occurs entirely from the great pond made by emptying the normal lake overflow behind the masonry dam.

Until the success or failure of the great dam can be determined the old dam will not be disturbed.

In the meantime the work of finishing the last details of the great construction job is going forward. The tremendous concrete lined tunnel through the solid rock of the south wall, where the water for the light plant is to be carried from the dam in pipes, is almost done.

A wonderful single arch concrete bridge spans the canyon from the end of this tunnel to the north wall to bear the pipes across the chasm. This is now nearing completion, an imposing structure more than 100 feet above the canyon bed.

The dam itself is done for the present. It has been topped with an ornamental concrete balustrade. Along the balustrade are set posts for single ball "ornamental lights" to make the great wall brilliant at night.

Just now the engineers are speculating whether the lights will ever be lit.

"We may want to keep it dark," said one yesterday, as he puzzled over the mystery of the sinking water.

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The taxation bureau of the Chamber of Commerce, in a report submitted to the trustees yesterday, said that following the report of the engineering experts in May, 1912, on the seepage encountered in the north bank of the Cedar river above the dam it recommended that work stop and a thorough examination of the north bank be made to determine the advisability of, proceeding with the dam construction.

"The recommendation was adopted by the chamber and transmitted to the city council," the report continues. "The council concurred in the recommendation of the report that an expert be employed to make a thorough investigation, but as one expert they desired was not immediately available they proceeded with the work, regardless of the protests.

"On November 8, 1911, the secretary rendered a report to the executive committee of the bureau to the effect that work on the Cedar river dam was being prosecuted inefficiently, and the committee took up the matter a second time.

"The consideration broadened into an investigation of the entire matter, leading to two public hearings, at which the matter of seepage through the north bank was gone into thoroughly. There was much diversity of opinion on the part of engineers regarding the extent of this danger, and the request of the bureau Dean Roberts, of the engineering staff of the University of Washington, who had first called attention to the character of the formation of the north bank, made an investigation. His report to the commmittee minimized the danger as shown by surface indications.

"As several hundred thousands had been spent by the city at that time in dam work, the bureau recommended that the work be finished by contract instead of day labor to the 1,555 level, but that further tests of the north bank be made immediately to determine if the danger pointed out by the expert really existed.

"The board of public works followed the recommendations of the committee and let a contract for the work, the city engineer in the meantime reporting that he had sunk test holes as recommended."

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Councilman Goddard at the meeting of the council committee of the whole Friday will introduce a bill calling for the appointment of an expert consulting engineer to examine the Cedar river dam project and to ascertain the probable extent of the seepage of water through the north bank of the river, and report recommendations for remedying this, if possible, in the least expensive and quickest form.