Annual Reports of the War Department

by the motion of the waves. This gauge could always be approached and could be read to a fractional part of an inch in the roughest weather. From May 25 to June 30, this gauge was read three times daily, and each gauge was read hourly during times of sounding on the shoal to which it related.

After the return of the party to Detroit, comparisons were made between the two gauges and the one at Cleveland, Ohio, and it was found that the zero of the Colchester gauge was 1.99 feet below high water of 1838 and 0.35 foot above the water surface shown on the chart (mean level of Lake Erie 1860-75), while the zero of Pointe Pelée gauge was 1.24 feet below high water of 1838, and 1.10 feet above the water surface shown on the chart. Expressed as elevations above mean tide at New York City, the different levels are as follows:

High water of 1838, 575.20 feet above mean tide; Pointe Pelée, zero, 573.96 feet above mean tide; Colchester, zero, 573.21 feet above mean tide; water surface of chart (mean level of Lake Erie 1860–75), 572.86 feet above mean tide.

Temporary bench marks were also established near each gauge for use in case the gauge should be displaced. At Colchester the bench mark was the top of a large bowlder in the gully at the foot of Dunn street and was 5.33 feet above zero of gauge. At Pointe Pelée, the beach mark was the top of a nail driven in the root of an ash tree at the edge of the woods abreast of the gauge and was 4.10 feet above the zero mark.

Hydrographic work. The object of the surveys being the reëxamination of certain localities where vessels had struck while drawing less water than was shown on the chart, it was of the greatest importance to obtain the minimum depth of water at each place. In order to do this it became necessary to employ the device known as the sweeping bar. As used on this survey, it consisted of a 24-inch gas pipe, 27 feet in length, held horizontally below the surface of the water by two small ropes bound to the bar about 8 or 9 feet from either end and passing up to the top of the water; each rope then passed over a pulley and was belayed to a stout beam that lay across the deck of the steamer just forward of the pilot house, the pulleys over which the rope passed being held in the ends of the beam where they overhung the sides of the boat. Both supporting ropes were so marked that the bar could be held horizontally and its depth below the water surface could be gauged according to the depth at which obstructions were looked for. With this device it was necessary for the steamer to move very slowly in order that the bar might hang vertically downward and not swing back and up, as would be the case were the steamer to move at a normal speed. Had the supports of the bar been made rigid—of vertical pieces of gas pipe, for example-so that the steamer could move rapidly, the first time an obstruction was struck the apparatus would have been so badly broken or injured as to cause great delay for repairs. On the other hand, should the bar swing back slightly and rise a foot, or even 2 feet, it was of no particular consequence, as the main use of the bar was as a finder, the steamer being backed and stopped whenever the bar struck, and the obstruction searched for with a sounding pole. Should the obstruction not be found in this manner, as was sometimes the case, then the bar was raised a foot and the steamer started forward very slowly. If the bar struck again it was raised another foot and the same process repeated until the bar passed over the obstruction, when it was lowered to its former depth and the survey continued. In order to tell when the bar struck, a man was stationed at each of the ropes that supported the bar, and kept his hand always in contact with the rope. A spare bar was always carried, in order to minimize delay in case of accident.

It was on account of the slow speed required of the steamer in carrying the bar or sweeping that the Scotia was so much better suited to the work than the C. W. Wells. The Scotia had a double engine, and could run as slowly as desired, whereas the Wells, having a single engine, would center if she attempted to go as slowly as was necessary for sweeping. The Scotia also was much smaller and lighter than the other boat, and could stop more quickly and was not so likely to run away from an obstruction that the bar had found,

Sweeping being the essential part of the survey, it became necessary to subordinate every other part of the work to this. In order to locate obstructions found by the bar the following method was adopted: Four buoys were anchored approximately in a parallelogram, two of the four sides of which were about 1,000 feet in length; these buoys being located instrumentally from the shore. A line 1,000 feet in length was then anchored along one of the 1,000-foot sides of the parallelogram and a similar line was anchored parallel to the first and 300 feet from it. These thousand-foot lines had every 50 feet marked upon them by a cork, which, floating on the water, could be seen from the adjacent boats. A small boat containing the sounding party would be rowed along one of these cork lines and soundings taken at each of the corks; the boat would then return on a line 50 feet from the first, the position of this line being estimated with sufficient accuracy from the cork lines on either side of the boat, and soundings would be taken abreast of each of the corks. In this manner the area of 300 feet by 1,000 feet would be covered with soundings 50 feet

apart. The steamer carrying the sweeping bar would follow the sounding boat, first covering the 25 feet next to the cork line, then the 25 feet next to this, and so on, making two runs to every one of the sounding boat. As the bar was 27 feet long there would be a slight overlapping were the steamer to keep a true course each time; should she vary slightly from her course, however, an obstruction would have to be very small to escape her, and by having the bar at a sufficient depth the chance of missing the shallow spots was practically avoided. The sounding boat, completing the given area before the steamer, would proceed to reel up the cork line first placed in position, and would then place it on the other side of the second cork line, parallel to it and 300 feet from it, thus inclosing a new area, which was surveyed in a similar manner to the first one. By this method an obstruction found by the sweeping bar could at once be located within a few feet of its position with respect to the soundings and the buoys. After the shoal proper had been surveyed such lines of soundings would be run as would suffice to develop the bottom in its vicinity. At Colchester quadrilaterals about a mile in length and 2,000 feet in width were sounded as follows: Three buoys were established in line, the middle one being about 1,000 feet from the other two. Three other buoys were established in the same way abreast of the first three, about a mile from them. All buoys were then located from the shore. One-half of this quadrilateral being 1,000 feet by about a mile in area would be surveyed by placing one of the 1,000-foot cork lines between two of the buoys and the other cork line between the two buoys opposite them. A small boat would then anchor at each of the two buoys which marked one of the long sides of this quadrilateral and the steamer would run between the small boats, being kept in range by flag signals from one of the boats. The steamer would run at a uniform speed, soundings would be taken from her on time and on important lines the sweeping bar would be carried very deep to ascertain whether or not any obstruction existed. After the line between the two buoys had been sounded in this manner the small boats would move opposite corresponding corks 200 feet or 300 feet or any desired distance from the buoys and the line between the two boats sounded as before. After the first half of the quadrilateral was surveyed in this manner, the cork lines were shifted to the corresponding buoys in the second half, and the survey was continued. This method was very flexible. With the limited time at the disposal of the party when it became necessary to hurry the work on account of threatening weather the lines of soundings could be placed farther apart, while, should closer examination of any special area prove necessary, the lines could be put closer together, the sounding party being entirely independent of the shore. Had any obstruction been found during the course of this work it was proposed to drop a buoy upon it, finish the line upon which the soundings were being made, and subsequently return to the spot that had been buoyed, and make a special survey of it in a similar manner to that employed on the shoal proper. As no obstruction was found during this work no special survey of this kind was required.

During the progress of the hydrographic work the gauge was read every hour, and the times of beginning and ending of each line of soundings were recorded. Every night after the return of the party to shore, all the soundings were reduced to zero of gauge and were then plotted upon the map at the first practicable opportunity.

RESULTS.

Shoal 3 miles north and west of Pelée Spit light-house. The first place surveyed in this vicinity was the shoal upon which 31 fathoms are shown upon the chart. This shoal was found to consist mainly of a ledge of solid rock, and the least depth found was 18.7 feet, as referred to the water surface of the chart, an area of about 1,430,000 square feet having been passed over by the sweeping bar.

During the past spring Capt. W. A. Grubb, the keeper of Pelée Spit light-house, noticed some ice remaining near this shoal after all the ice had disappeared elsewhere. He had the forethought to establish ranges on the shore in line with this ice, and after the survey of the above-mentioned shoal was finished one of Capt. Grubb's ranges was followed out and a large shoal was discovered about half a mile to the northeast of the first one, where good water is shown on the chart. This shoal was surveyed and three points of minimum depth were discovered, one having 16.1 feet of water on it as reduced to the water surface of the chart, over a ledge of rock; another 13.5 feet over an old wreck laden with iron ore, said to be the Nicholls, sunk in 1879 after the former survey was finished, and the third 13.5 feet over a cluster of bowlders. On this shoal an area of 1,100,000 square feet was covered by the sweeping bar. Lines of soundings were run connecting the two shoals, and good water was found between them.

Had it not been for the ranges established by Capt. Grubb it is doubtful if the party would have discovered the new shoal in this locality. They certainly would not have done so without a great loss of time. It is important that as dangerous a shoal as this, so close to the track of vessels, should have a name so that it would

quickly catch the eye of anyone using the chart. Capt. Grubb's assistance having been entirely voluntary, and having been of great use to the survey, I have therefore to suggest the name of "Grubb Reef" for the two shoals at this point.

The importance of having all dangerous shoals like this one plotted upon the chart at the earliest possible moment is shown by the fact that a vessel is reported to have grounded upon the new shoal at this point shortly after the survey party left Pointe Pelée. She is reported to have struck the spot where the wreck of the Nicholls lies, and to have been delayed six or seven hours before being able to lighter off. A wrecking outfit was telegraphed for to Amherstburg and arrived shortly after the vessel had left the shoal. All the expense thus incurred would doubtless have been saved had the shoal been marked upon the chart.

Shoal making out from Littles Point, Lake Erie.-At this locality a shoal was marked upon the chart 1 mile south of Colchester Dock, with a least depth of 16.5 feet upon it. A new shoal was reported three-eighths of a mile south of this one, and was said to be quite extensive and to consist of large bowlders. No sign of this latter shoal was discovered by the survey party, but the shoal shown on the chart was found to be more extensive than there indicated, and to consist of sand, clay, and mud, in which are embedded a large number of bowlders, some of which stand as high as 6 feet above the bottom. The least water was found 1 mile south of Colchester Dock, and is 12.35 feet as reduced to the water surface of the chart. An area of 4,500,000 square feet was swept with a sweeping bar, and the usefulness of this device was fully demonstrated, as the sounding poles and lead lines would invariably give from 4 to 6 feet more water than was found by the bar.

After the shoal had been surveyed lines of soundings were run all around it, and about 2 square miles of area covered. South of the shoal, where a new shoal was reported, lines were run 200 and 300 feet apart from the shoal to the south side of the track of vessels. On these lines the sweeping bar was carried at a depth of 27 feet below the surface and did not strike; thereby demonstrating that no such shoal as was reported was in existence. Whoever located it was doubtless on the shoal marked on the chart, and overestimated his distance from the shore. As it would be well for this shoal to have a name, I have to suggest that it be called "Grecian Shoal," from the name of the vessel that struck upon it in July, 1891.

ESTIMATES AND COST.

The estimate for the survey of the shoal off Pointe Pelée was $1,000. The cost of the work was $553.09. The estimate for the survey of the shoal off Littles Point was $610. The cost of the work was $587.59. Total estimate, $1,610; total cost, $1,140.68. The party was very much delayed by bad weather. Had the month of June been no more stormy than it ordinarily is, the work would have been finished in a week and a half to two weeks' less time, and the cost would have been proportionately reduced.

In conclusion, I desire to state that Recorder Herman Kallman, jr., who had personal charge of all the offshore work, proved himself highly energetic and efficient, and it was largely due to his efforts that the party were enabled to complete their work before the close of the fiscal year. Respectfully submitted.

CHARLES S. RICHÉ,

First Lieutenant, Corps of Engineers, U. S. Army,

Col. O. M. POE,

Corps of Engineers, U. S. Army.

REPORT OF MR. E. 8. WHEELER, ASSISTANT ENGINEER.

UNITED STATES ENGINEER OFFICE, Sault Ste. Marie, Mich., July 5, 1892. COLONEL: I have the honor to submit the following report upon the operations connected with the survey of the Northern and Northwestern Lakes, St. Marys River, for the fiscal year ending June 30, 1892:

I received your orders in February to begin a survey of St. Marys River. This survey to be of sufficient accuracy to make a chart in general, similar to the lake survey charts with the hydrography of the channels of about the same accuracy as the usual harbor surveys.

The following surveys which have already been made were to be utalized as far as possible:

(1). United States lake survey made in 1853 and 1854. The shore line and hydrog

raphy of this survey to be used excepting where improvements have been or will be made.

(2). Survey made under the direction of Gen. Weitzel in 1879; this is a survey of the channel only.

(3). Precise levels which have been brought from sea level to Lake Superior at Marquette by the United States Lake Survey.

The work required under your orders was as follows:

(1). A primary triangulation connecting the Lake Survey triangulation in the east end of Lake Superior with that in the north end of Lake Huron, with the necessary base lines and azimuth determinations.

(2). Minute hydrography of those points in the channel which have been dredged or otherwise changed since the previous surveys.

(3). Topography of that portion of both banks of the river which is conspieuous from the decks of vessels passing through the river.

(4). The determination of the latitude, longitude, and azimuth of at least one point in the triangulation.

(5). Carrying precise levels westward as far as Bay Mills, for the purpose of making accurate tide-gauge readings at this point.

The actual work of this survey was begun in the last days of May. Assistant Engineer Ripley with a party of about 15 men, the tug Myra, and the quarter boat Swallow made a minute survey of the shoals at Sailors Encampment. Mr. Ripley's report is attached herewith:

UNITED STATES ENGINEER OFFICE,
Sault Ste. Marie, Mich., July 4, 1892.

SIR: The limestone shoal at Sailors Encampment was selected for beginning the hydrographic work of resurvey of St. Marys River, Michigan.

Five stations were located for continuing the triangulation of river survey of 1879 from Sailors Encampment to head of Mud Lake.

Each station was marked with a piece of limestone about 1 foot square in which was drilled a hole one-half inch in diameter and 3 inches deep. The stones were placed 3 feet under ground and a wooden tripod built and placed in position over each stone.

The angles were read with the Piston & Martin theodolite, and each triangle closed within three seconds. The present steamboat channel is on the Canadian side and has three courses from angle above shoal to the can buoy in Mud Lake. channel was selected on the American side of the river with only one course, and the improvements required will be out of the way of passing boats.

Soundings were taken 10 feet apart over an area 400 feet wide and 3,120 feet long, also 30 by 200 feet apart for the full width of the river for a distance of 3,000 feet. Very respectfully, your obedient servant,

Mr. E. S. WHEELER,

Assistant Engineer, etc.

JOSEPH RIPLEY,
Assistant Engineer.

Assistant Engineer O. B. Wheeler, of the Missouri River Commission, was directed by you to begin the triangulation. Mr. Wheeler reported on the 21st of May, 1892, with 4 assistants from the Missouri River Commission; selected a base line 2 miles in length on Portage avenue. This was measured four times with satisfactory results; he also planned six stations of the triangulation and measured the angles at four of them. Azimuth was observed from a station about 1 mile from the base. Two of Mr. Wheeler's assistants carried a line of precise levels from the masonry of the lock walls to Bay Mills.

Mr. Wheeler's report is attached herewith:

UNITED STATES ENGINEER OFFICE, Sault Ste. Marie, Mich., June 28, 1892. SIR: Agreeably to the following instructions I reported at your office, at this place, on May 21, 1892.

DETROIT, MICH., May 9, 1892.

SIR: As soon as relieved from duty on the Missouri River Commission, for temporary service in connection with the resurvey of St. Marys River, Mich., you will proceed to Sault Ste. Marie, Mich., and report for duty to Mr. E. S. Wheeler, assistant engineer in local charge of the public works at that place. The travel indicated is necessary for the public service.

Very respectfully,

Mr. O. B. WHEELER,

Assistant Engineer.

The importance of having all dangerous shoals like this one plotted upon the chart at the earliest possible moment is shown by the fact that a vessel is reported to have grounded upon the new shoal at this point shortly after the survey party left Pointe Pelée. She is reported to have struck the spot where the wreck of the Nicholls lies. and to have been delayed six or seven hours before being able to lighter off. A wrecking outfit was telegraphed for to Amherstburg and arrived shortly after the vessel had left the shoal. All the expense thus incurred would doubtless have been saved had the shoal been marked upon the chart.

ESTIMATES AND COST.

CHARLES S. RICHÉ,

First Lieutenant, Corps of Engineers, U. S. Army.

Col. O. M. POE,

Corps of Engineers, U. S. Army.

REPORT OF MR. E. S. WHEELER, ASSISTANT ENGINEER.

The following surveys which have already been made were to be utalized as far as possible:

(1). United States lake survey made in 1853 and 1854. The shore line and hydrog

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Annual Reports of the War Department, Volume 4