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Thus I was at once, as it were, deprived of the services of eight of my most experienced assistants.

It has always been my aim to so organize each party, that in case its chief should be removed or become incapable of attending to his labors, the duties of the survey would not be suspended or materially retarded; that is, to have two persons in each party capable of conducting the work assigned to it. The distant and inaccessible localities in which the survey has been carried on caused the adoption of this rule, and numerous instances have occurred, by an officer being relieved while in the field or before the work of his party was computed and projected, or by sickness or otherwise, when the necessity of the rule has been made apparent.

I found, however, that it would be impossible to effect such an organization for the present season.

I know of no school other than the survey, where the experience requisite to take charge of a party can be obtained. I was therefore obliged to organize with the force at my command, and it was only because the funds available for the present year were less than two-thirds the amount applicable to last year's work, and consequently the operations were to be on a greatly reduced scale, that I was able to effect an organization in the least satisfactory.

Instead of three steamers, five shore parties, three astronomical parties, and three river parties in the field, the force this year is reduced to two steamers, two shore parties, six astronomical parties, and two river parties. The increase in the number of astronomical parties was rendered necessary to compensate for the loss of last season's work, due to the want of instruments.

The remarkably unfavorable spring caused a late departure for the field. The parties left this city as follows:

The steamer Ada, First Lieutenant J.C. Mallery, Corps of Engineers, in charge, having on board the topographical and hydrographical parties, under charge of Assistants J. R. Mayer and A. C. Lamson, sailed on the 26th of May, 1869.

The river gauging party, under charge of Assistant Lewis Foote, left for Youngstown, New York, on June 3, 1869.

The river gauging party, under charge of Assistant D. F. Henry, left for St. Clair, Michigan, on June 5, 1869.

The steamer Search, First Lieutenant James F. Gregory, Corps of Engineers, in charge, having on board the astronomical and triangulation parties, under charge of Assistants 0. B. Wheeler, G. Y. Wisner, G. A. Marr, and A. R. Flint, sailed on the 6th of June, 1869.

The astronomical and triangulation parties, under charge of First Lieutenant E. H. Ruffner, Corps of Engineers, and Assistant E. S. Wheeler, left this city on June 8, 1869.

Their respective fields of operations are as follows:

First Lieutenant James F. Gregory, Corps of Engineers, was assigned to the command of the party on board of the steamer Search, for general off-shore duty, and to move and supply the primary triangulation and astronomical parties, and also to exercise general supervision over the parties in the field.

First Lieutenant E. H. Ruffner, Corps of Engineers, was assigned to the command of the three primary triangulation and astronomical parties in the western part of the lake, having himself the immediate charge of one division, and Assistants G. Y. Wisner and E. S. Wheeler to take charge of the other two sections.

First Lieutenant J. C. Mallery, Corps of Engineers, was assigned to the command of the party on board the steamer Ada, for off-shore duty near and around the Apostle Islands, and also to survey the outer islands of the group connecting with the work of the shore parties.

Assistant J. R. Mayer was assigned to the command of a shore party, commencing work at the most eastern point reached by the survey of the “head of the lake” in 1861, and continue east to meet Assistant Lamson, making also a survey of the western Apostle Islands.

Assistant A. C. Lamson was assigned to the command of a shore party, to commence work at the most western point reached by Lieutenant Griffith's party in 1868, and to continue west to meet Assistant Mayer, making also a survey of the eastern Apostle Islands.

Assistant D. F. Henry was assigned to the command of the parties to continue the gauging of the rivers.

Assistant O. B. Wheeler was assigned to the charge of the three divisions of the astronomical and primary triangulation parties in the eastern portion of the lake, having for chiefs of divisions Assistants A. R. Flint and G. A. Marr.

On the 5th of June, 1869, Brevet Major Jared A. Smith, United States Army, captain Corps of Engineers, reported for duty as my senior assistant. He was at once sent into the field as the immediate chief of the party on board the steamer Ada, and given a general supervision of all field operations, with instructions to issue such orders in my absence as he might find requisite to insure uniformity in the work and the faithful performance of the duties of the survey.

At the date at which this report commences all the parties were at their posts, and busily engaged in the discharge of their respective duties.

I may add that I visited the parties myself in July and also in August. They were only making tolerable progress, the season having been by far the worst for field operations ever known in the history of the survey. I think it probable that the shore-line and detailed topography and hydrography of Lake Superior will be finished the present season, but that a portion of the primary triangulation and general hydrography will remain incomplete. Respectfully submitted.

W. F. RAYNOLDS,

Lieut. Col. of Engineers, But. Brig. Gen. Bvt. Brig. Gen. A. A. HUMPHREYS,

Brig. Gen. and Chief of Engineers, Washington, D. C.

The following is an estimate for continuing the survey of the northern and

northwestern lakes for the fiscal year to commence July 1, 1870, and end June 30, 1871, on the same scale and with a similar organization to that employed during the season of 1868:

For three parties for hydrographical duty, general triangulation, reconnoissance, &c., one for each of the lake survey steamers Search, Surveyor, and 'Ada, the cost of each party will be as follows: 1 assistant, 183 days, at $4 80 per day.

$878 40 1 assistant, 183 days, at $3 60 per day.

658 80 1 assistant, 183 days, at $2 50 per day

457 50 1 recorder, 183 days, at $1 25 per day

228 75 1 sailing master, 365 days, at $2 75 per day..

1,003 75 1 mate, 183 days, at $2 per day

366 00 1 steam engineer, 365 days, at $2 75 per day...

1,003 75

1 assistant engineer, 183 days, at $2 per

day. 1 carpenter, 183 days, at $2 per day 1 steward, 183 days, at $1 50 per day 1 cook, 183 days, at $1 50 per day. 1 second cook, 183 days, at $1 per day 4 firemen, 183 days, at $1 25 per day 14 seamen, 183 days, at 90 cents per day Subsistence for the above 30 persons, 183 days,

at 50 cents each per day .. 450 tons coal, at $8 per ton, (for fuel)

$366 00
366 00
274 50
274 50
183 00

915 00
2, 305 80

2, 745 00
3, 600 00

$46, 880 25

Total for one hydrographical party....

15, 626 75 For three hydrographical parties .

For three astronomical, magnetic, and primary triangulation parties as follows: 1 assistant, 183 days, at $4 80 per day

$878 40 1 assistant, 183 days, at $2 50 per day

457 50 1 recorder, 183 days, at $1 25 per day.

228 75 1 cook, 150 days, at $1 50 per day.

225 00 5 men for boats crews and laborers, 150 days, at 80 cents per day ..

600 00 Transportation of parties, provisions, camp equipage, &c., to and from the field....

500 00 Subsistence for 9 men, 150 days, at 50 cents

675 00

per day

10, 693 95

Total for one party

3,564 65 For three parties....

For five topographical and hydrographical parties to survey shore-line and adjacent topography and hydrography, the cost of each party will be as follows: 1 assistant, 183 days, at $4 80 per day

$878 40 1 assistant, 183 days, at $3 60 per day

658 80 1 recorder, 183 days, at $1 25 per day.

228 75 1 foreman, 165 days, at $1 40 per day.

231 00 1 steward, 165 days, at $1 40 per day ..

231 00 1 cook, 165 days, at $1 40 per day

231 00 1 waiter, 165 days, at $1 per day

165 00 2 leadsmen, 165 days, at 90 cents per day.

297 00 2 chainmen, 165 days, at 80 cents per day

264 00 14 boatmen, 165 days, at 70 cents per day..

1, 617 00 Subsistence of above 25 persons for 165 days, at 50 cents each per day

2,062 50 Expenses in purchase of tools, buoys, flags,

rope, leads, lead lines, materials for stations, camp and mess equipage, &c....

600 00 Transportation of 25 men to and from the field, at $20 each...

1, 000 00 Expenses of transportation of provisions, camp equipage, &c., to and from field, at $250

500 00

each way

Total for one party

8, 964 45 For five topographical and hydrographical parties.

44, 822 25 $10, 492 65

For three parties for ganging the outflow of rivers, the expense of each will be as follows: 1 assistant, 183 days, at $3 60 per day

$658 SO 1 recorder, 183 days, at $1 25 per day.

228 75 6 men, 165 days, at $2 per day, including board..

1,980 00 Board of 1 assistant and 1 recorder, 165 days, at $1 per day

330 00 Transportation to and from the field

300 00 Total for one party.

3, 497 55 For three parties for gauging outflow of rivers.

Office and miscellaneous expenses: Office rent and fuel for one year .

$1, 800 00 Pay of two draughtsmen for reducing maps

for engraving, one year of 365 days, at $5 30 each per day..

3, 869 00 4 assistants, chief of parties, 182 days, at $5 30 per day

3, 858 10 5 assistants, 182 days, at $1 10 per day

3, 731 00 2 assistants, 182 days, at $3 50 per day

1,274 00 1 assistant, 365 days, at $4 10 per day

1, 496 50 1 assistant, 365 days, at $3 per day

1,095 00 3 copyists and computers, 365 days, at $2 30 each per day..

2,518 50 1 office attendant, 365 days, at $1 50 per day.....

547 50 3 steamers in ordinary, at $1,000 each....

3,000 00 Commutation of fuel and quarters for 5 officers of the Corps of Engineers....

2, 750 00 Traveling expenses of superintendent and

assistants while attending to the duties of the survey.

750 00 Expenses in office, drawing paper, and materi

als, stationery, nautical almanacs, &c ..... 600 00 Expenses of meteorological and tide-gauge observers for one year

4,000 00 Total estimate for office and miscellaneous expenses.. Add 10 per cent. to cover contingent and other expenses,

such as purchase of tools, boats, camp equipage, &c...

31,289 90

14, 417 90

Total estimate

158, 596 90

Respectfully submitted.

W. F. RAYNOLDS,
Lieut. Col. of Engineers, But. Brig. Gen.

A.

OFFICE LAKE SURVEY, July 1, 1869. SIR: I have the honor to submit the following report of the progress made by the river-gauging parties under my charge during the past

rear:

Before the close of the season of 1867, I began to have great doubt of the correctness of the results obtained by means of floats, on account of the unavoidable errors of that method.

These errors may be classed under the following heads:

1. The error of the area of cross-section. In order to obtain the true area it would be necessary to know the exact depth of the river past the whole base line. Generally we sound out two or three cross-sections carefully, and assume their mean to be the mean area of the river. Then, finding the mean time of passage of floats past the base line, the velocity of the river is obtained, and the product of this into the mean area has to be taken as the true discharge. I noticed that in the places chosen, which were the best that could be found, that the irregularities of the bottom were such that the product of the mean velocity into the area of the river, at the upper and lower end of the base, would make a difference of several thousand cubic feet per second, and I was obliged to take the mean as the discharge, though I knew that it conld not be correct. Again, the irregularities of the bottom affect the current, and the floats are differently influenced at different depths, so that, although the computed discharge might happen to be correct at one depth, it would not be so at another.

2. The irregularities of flow.These, together with the irregularities arising from the form of the bottom, are shown, by the fact noticed in the last report, that often when two floats were put out at different depths, say five and ten feet, the rear one would gain upon and sometimes even overtake the forward one. This sometimes happened when the floats were at the same depth, but not often. These irregularities make the determination of velocity very uncertain, and a very large number of observations would be necessary to give an approach to accuracy.

3. The difficulty and uncertainty of the location of the floats.—The length of the base lines were one-third the distance of the furthest float from them, and the stations were connected by telegraph, so that the time of passage of the float past one station was instantaneously communicated to the observer at the other. But when a float was moving at a rate of over two feet a second, it was impossible to follow it with the telescope by means of the tangent screw, so that the instrument had to be moved by hand, and it was only by a lucky chance that the hairs were brought exactly on the float when the signal came. This made an uncertainty in the location; and, as the velocity is slower near the banks, the computed velocity would be too large or too small, as the error was on one side or the other. Again, the floats rarely ran in the same vertical plane or parallel to each other. Often in still weather, when the boat was anchored near the center of a division, part of the floats would run out of the division altogether, or more than one hundred feet out of their proper plane, the calculated path of the float being sometimes as much as three feet longer than the distance between the cross-sections. This would, of course, be a cause of error, when we attempted to reduce them to the center of the section to obtain the mean velocity.

4. A floating body moves faster than the water in which it is immersed. Navier has investigated this subject, and gives a formula for the computation of the error. It depends upon the slope of the surface, the displacement of the body, and area of its greatest transverse section. Its amount, however, is small and not worth the trouble of computing.

5. The upper float drags the lower. This is also small, and depends upon the relative sizes of the floats and velocity of current.

6. The upper and lower floats are connected by a cord one-twelfth in diameter. This also drags the lower float an amount in direct proportion to the length and size of the cord. But the cord can never be perfectly

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