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 34 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 demoustrated, 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. B. REPORT OF MR. E. S. 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 conspicuous 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, 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. A 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 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. BASE LINE. The first work was the selection of ground suitable for the measurement of a 2mile base line, to be measured with the steel tape by night. The location of this base line was finally on Portage avenue, in this city, and extended from Bingham street nearly to the Little Rapids lining, for the most part of the way, through the center of the street-car track, which track was not then in use. The staking out and measuring of the line was identical with the method used in 1885 under the Missouri River Commission and fully reported in reports for 1885-'87. The same "adjuster" as there used was used here, and a standard tape and thermometers belonging to the Commission, together with a standard thermometer 21 inches in length, belonging to Mr. E. S. Wheeler, were used. Three complete measurements were made on the same date (namely, June 1), the first and last measurements agreeing within one-tenth of an inch, the middle one differing by less than one-half inch from either of the others. A 500-foot ste 1 tape, belonging to the office here, was standardized by measuring a commensurate distance of 1,500 feet measured also with the 300-foot standard tape. A copy of the adjuster and reel of the Commission was made for use with the 500-foot tape. TRIANGULATION STATIONS. The stations of the base line were so located that the triangulation could be carried off on either side of it. The first station off the base was upon the Ashmun street hill, 14 miles from the west base station, and it was selected also as the azimuth station, while the marks (or lantern) was on station "west base." The second station off the base was in Canada, 3 miles from west-base station. The four stations mentioned constitute the first quadrilateral. The fifth and sixth stations are on Sugar Island and Rankins Mountain Canada, respectively, and with the third and fourth mentioned constitute the second quadrilateral. The seventh station is on Larks Ridge, a commanding ridge, about 2 miles southwest from New Fort Brady. All seven stations are described in the notebook and are marked, six with the regulation stone 18 by 18 by 4 inches with a brass center bolt, set 3 feet or more under ground, the sixth being on naked rock, with a half-inch hole drilled in the rock, in which hole is cemented a 20-penny spike with head down. This spike stays the foot of a target. The station is on the highest point of rock within a half-mile radius of the station. At five of the stations portable tripods answer the purposes of a station. At the first station in Canada it was necessary to erect a 21-foot tripod with a target platform at 24 feet above the ground, and on Sugar Island a 57-foot tripod with a 60-foot target platform was necessary, to save the extensive cutting of timber. Assistant Engineer Glen C. Balch successfully supervised the construction of the latter station. Both stations were built of pecled round timber and are models of their kind. PLAN OF TRIANGULATION. A quadrilateral system with a minimum limit of a 30° angle in triangles used in computation is contemplated. This is to be carried on from an 11-mile line between the sixth and seventh stations in connection with the fifth reaching Gros Cap or Iroquois Point, going above, or a point in Canada back of Lake George, going below, looking over Sugar Island from the seventh station. A point south of Waiska Bay should be selected for good conditioned triangles, going above. Also a point south from here about 12 miles on Sand Hill or Stony Ridge between the Meridian and Mackinac roads, going below. Stations of any great height will be required only on the Michigan side to get above the timber. AZIMUTH AND ANGLE READING. The azimuth and angle readings have been made with the Troughton and Simuns Theodolite, No. 1, 14-inch limb, fully described in Professional Papers No. 24, Corps of Engineers, U. S. A. Complete azimuth observations on Polaris near and at elongation with the necessary time-star observations have been secured on two nights. These observations were so satisfactory (differing at elongation by only 1.6 seconds) that it was not considered necessary to obtain a third night's observation, especially as the time for angle reading was limited. No star at western elongation was available or it would have been read upon. One half of the observations were from image of the star from an artificial horizon, thus doing away with the reading of the level, a method most highly to be commended. The mark at west base station, was a light through a vertical slit two-tenths of an inch in width. Fogs and clouds cut off the work on many nights. At three of the stations a portable station 6 feet in height has been used, and the readings over the base line were made before 6 a. m., before the street cars were in motion. The reading on first quadrilateral are completed-three of the triangles closing on the first attempt within the primary limit of 3 seconds, the fourth closing outside this limit was reread at one station. The remaining three stations are approximately located. Vertical angles were read at all stations occupied. The readings on angles and azimuth were all made by Assistant Engineer E. B. Wheeler, and recorded by Assistant Engineer Glen C. Balch or myself. PRECISE LEVELS. A line of precise levels was run from B. M. "F." of the Ship Canal to the water gauge established at Bay Mills, on a bay which may be considered a part of Lake Superior proper, to find the slope of the St. Marys River above the canal. The report of the assistant engineers who did the work is herewith appended. An approximate result from the few water-gauge readings at Bay Mills indicate a slope of about 0.42 foot. I desire to commend highly all the assistant engineers who aided me in the work. Very respectfully, Mr. E. S. WHEELER, U. S. Assistant Engineer. O. B. WHEELER, UNITED STATES ENGINEER OFFICE, DEAR SIR: Following your instructions a line of precise level was run from B. M. "F" on the northwest corner of the lock to a gauge in Waiska Bay. The length of the main line was 14 miles and 20 yards. The limit of error allowed was 3mm VK, where K represents distance in kilometers. The main line was run in seventeen sections. Of the seventeen, eleven checked on first trial, three were run three times, two were run four times, and one was run five times. In two cases only did the error exeeed 9mm to the mile on the first trial. The adjustment of the bubbles on the rods was tested daily. The adjustments for collimation and inclination were tested morning and evening, except in one or two cases where prevented by rain. The maximum error allowed in collimation was 2mm. The maximum error allowed in inclination was two divisions of the level tube. Four permanent and seventeen temporary bench marks were established and described in the notebooks. The zero of gauge in Waiska Bay was found to be 1.1541 meters 3.78 feet below B. M., "F." Very respectfully, your obedient servants, Mr. O. B. WHEELER, U. S. Assistant Engineer. B. J. THOMAS. A. O. WHEELER. The following instruments for use on this work have been received: 1 Negus chronometer, No. 1524; 2 Troughton & Simms theodolites, Nos. 1 and 3, with 14 inch limbs; 1 Wurdemann zenith telescope, No. 12; 1 Wurdemann transit, No. 1; 1 chronograph, by Bond & Son. All of these instruments were received in good order, except the zenith telescope, which had evidently been injured in transit. All work was stopped on the 30th of June. Assistant Engineer Wheeler returned to the Missouri River Commission, taking with him the base-measuring apparatus. Very respectfully, your obedient servant, Col. O. M. POE, Corps of Engineers, U. S. A. E. S. WHEELER, |