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Large quantities of arms of war are made here. It is a very convenient distributing point, and its fine approaches from the ocean will give it a large opportunity for foreign trade as soon as the contemplated deep channel is secured.

The total number of vessels that arrived at the port of Providence during the year 1878 was 5,580, of which 1,975 were steamers from Baltimore, Philadelphia, New York, Fall River and Newport; 3,440 were barks, brigs, schooners, sloops and barges, from various American ports, and 112 foreign barks, brigs and schooners. Providence is in the Providence collection district, and that place is a port of entry. The amount of revenue collected there during the fiscal year ending June 30, 1880, was $405,652.73.

TIDAL OBSERVATIONS MADE IN OCTOBER AND NOVEMBER, 1879.

With this report is submitted an account of tidal observations made by Mr. H. A. Bentley, assistant engineer, who has superintended the works of improvement.

The mean rise and fall of tides here is given on the Coast Survey charts as 5.1 feet. A mean of three and a half years' observations of a self-registering gauge gave it as 4.53 feet. The former is known to be excessive and the latter was thought to be too small. Our observations of 1879 prove this to be so and make the mean rise and fall 4.7 feet, the determinations agreeing very closely with those made in 1853 by Lieut. W. S. Rosecrans, United States Engineers. Mr. Bentley's report is a valuable contribution to this subject, and shows the caution that is required in accepting local data about tides.

July 1, 1879, amount available.....

MONEY STATEMENT.

Improvement of Providence River aud Narragansett Bay.

$98,635 69

Amount appropriated by act approved June 14, 1880..... 60,000 00

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Amount (estimated) required for completion of existing project..... 330,000 00 Amount that can be profitably expended in fiscal year ending June 30, 1882...

100,000 00

Improvement of Providence River-Removal of Bulkhead Rock.

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REPORT OF MR. H. A. BENTLEY, ASSISTANT ENGINEER.

ENGINEER OFFICE, UNITED STATES ARMY,
NEWPORT, R. I., June, 1880.

GENERAL: I have the honor to submit herewith the following report on the tides of the Providence River, Rhode Island:

The first tidal observations here of which we have record are those made by Lieut. (General) W. S. Rosecrans, Corps of Engineers, U. S. A., who, in Decem ber, 1852, established a gauge, which was observed from December 11 to 17, 1852, and from April 12 to May 31, 1853. The mean of these readings, 94 of high and 90 of low-water, would make the rise and fall 4.66. Extreme range between lowest low-water and highest high-water, 7.61 feet. Mean high-water on gauge read 5.85; mean low-water, 1.19; highest high tide, 7.88; lowest low tide, 0.27. Both day and night tides were taken. A note on the record states that the zero of this guage corresponds with the low-water reference of Cushings chart of Providence Harbor. A better mean range of tide can be obtained by taking from these observations those of a lunation and deducing it from that. Using the lunar month between April 15 and May 13, inclusive, the mean rise and fall is 4.62.

The subjoined is a table of the observations of Lieutenant Rosecrans in 1853. Those made in 1852 were for seven days only, and were interrupted so that they are of little or no value and they are not given.

Record of tide gauge kept at Providence, R. I., from April 12, 1853, to May 31, 1853, under the direction of Lieut. W. S. Rosecrans, United States Engineer.

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The mean high-water plane of these observations was adopted as the city reference by Providence. In 1872 a survey of the Providence River between Fox Point and Field's Point was ordered by Congress and was made under your direction by me. At this time the city of Providence had borrowed from the United States Coast Survey a self-registering tide-gauge; this was running very well, and the city official in charge permitted us to take the record of this gauge for the lunation August 4-31, 1872, for the purpose of getting a mean low-water plane to refer the soundings of the survey to. These readings gave the mean rise and fall 4.63 feet. In 1873, while making a survey of the Pawtucket River, the readings of this gauge from May 22 to December 28 were taken, and the mean rise and fall for this period was computed to be 4.548 feet. This gauge is still at Providence, and has been most of the time in rnnning order. A mean taken of three and one-half years of the best of these observations gave a rise and fall of 4.53.

The mean rise and fall given on the Coast survey charts is 5.1 feet. The selfregistering gauge was at first located on the gas company's wharf; it was changed to Hill's Wharf, and then to its present location on the city wharf. These changes of position, and the varying difference between the registering scale and the tide-staff used for comparison made our attempts to arrive at a definite point for mean low-water very unsatisfactory.

To settle this point, and to be enabled to decide which of the above given ranges of tide was the best, the observations of which the following table shows the results were made:

Record of tide gauge kept at City Wharf, Providence, R. I., from October 3, to November 29, 1879.

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The mean rise and fall of these two months is 4.73; mean low water on the staff, 5.33; mean high-water, 10.06. This staff gauge is a plain board, graduated to feet and tenths; it is located at the city wharf, a few feet distant from the self-registering gauge; it was carefully observed each day, the night tides being omitted. The self-registering gauge was "running" at this same time, and through the kindness of Mr. Samuel M. Gray, city engineer of Providence, we have been furnished with a copy of the record. For the purpose of comparison, the following diagram of the tidal zone for the month of November, 1879, was made. On this diagram is shown the recorded heights of both gauges at high and low tide for each day of a lunation. The dotted lines indicate the lines of the staff gauge, and the full lines those of the self-register. They were platted by using as a common line the line of mean level.

The diagram shows the line representing the staff-readings at high tide to be generally above the line representing the self-register; and in the case of low-tide, the staff-line to be generally below the self-register. This difference, at high tide varying between 0.05 of a foot and 0.35 foot, and at low tide between 0.05 and 0.5 foot, indicates that this self-registering tide-gauge does not record the full rise and fall. The difference in the mean rise and fall for this lunation was 0.11 foot. Whether this difference is a constant quantity caused by frictional or other resistance in the running gear of the self-registering gauge, our observations are not extended enough to decide, but we have two lunar-months of readings actually observed and one month's observations made in the same way by Lieutenant Rosecrans in 1853, both of which give a greater rise and fall than the mean of the self-register. I would therefore recommend that the range of tide indicated by our observations in October and November, 1879, be adopted, and that the mean rise and fall be taken as 4.7. Mean low-water is referred to a bench mark which is the top of the southeast corner of the west abutment of the Point Street bridge; its height is 12.29 feet. A comparison with the city reference (Rosecrans' high-water) shows a difference of but 0.01 foot, so that for all purposes this reference may be considered correct and mean low-water taken as 4-7 feet below it.

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The improvement of this harbor as projected was completed during the fiscal year ending June 30, 1879, and was so reported in the annual report for that

year.

A resolution of the House of Representatives, February, 1880, was passed, calling for "information concerning the obstructions at the entrance to the inner

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