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TABLE XVII.-Showing the daily discharge, readings of water gauge, 8c.-Continued.

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TABLE XVIII.--Showing the daily discharge, reading of water gauge, and direction of wind in

the St. Lawrence River, 1868.

Date.

Date.

June 15 3. 23 D., 8. 0.938 256, 301

16 3. 24 Calm: 0.9812 268, 186 17 3. 35 D., 7.7 0.963 263, 913 18

3. 27 D.,10.5 1.0446 285, 530 23 3. 28 D., 8.8 0.949

259, 700 24

3. 11 Up, 7.4 0.954 265, 830 25 3. 22 D., 2.9 0.946 263, 484 26 3.38 D., 10.6 1.016 278, 435 29 3.17 1., 5.9 1. 019 278, 007

30 3.31 D., 9.0 0.976 267, 217 July 1

3.28 D.,11.8 0.988 268, 430 2

3. 25 D.,10.7 0.987 269, 811 3 3. 31 D., 8.6 0.999 273, 417 7

3. 12 D., 1.4 1. 023 274, 307 8 3.17 Up, 4.9 0.978 266, 917 9 3. 12 Up, 2.8 1. 067 290. 700 10 3. 20 D., 1.6 1. 110 300, 207 11 3. 21 D., 9.4 1. 061 289, 655 13 3. 23 D.,10.0 0.993 271, 303 14 3. 23 D., 8.1 0.987 269, 673 15 3. 23 D., 4.8 | 1. 012 276, 459 20 2. 87 UP, 9.2 0.900 243, 716 21 3. 02 D., 4.6 0.9636 262, 066 22 2.91 UP, 4.3 1. 039 281, 905 23 2. 80 Up, 1.9 1.051 284, 502 24 3. 04 D., 3.1 1. 025 278, 879 25 2. 88 D., 2.0 0.979 265, 370 27 2. 96 D., 4.5 0.990 268, 891

1.214 5
1. 223 5
1. 247 5
1. 352 10
1. 230 8
1. 263 4
1. 250 6
1. 267 9
1.314
1. 263 5
1. 270
1. 280 23
1. 292 9
1. 303
1. 265
1. 378 5
1. 470 7
1. 373 2
1. 298
1. 278
1. 263 6
1. 160
1. 243
1.344
1, 361
1. 322 3
1. 265
1.283 22

July 28 2.99 D.,10.0 1. 023 278, 028 | 1. 323 10
29
2. 92
Calm. 1. 007 273, 283

1. 299 2
31 2. 91 D., 7.7 1.000 271, 267 1. 290 3
Aug. 3 2.95 Calm. 1.041 282, 681 1.347
4 2. 77 Up, 4.5 1,049

283, 783

1. 352 5 2.77 Up,5.00 0.942 254, 713 1. 213 7 6 2. 80 Up, 2.8 1. 047

283, 422 1. 352 10 2.91 D., 3.2 0.980 265, 860 1. 265 6 13 3. 07 D., 3.4 1.019

277, 416

1.311 5 14 3. 12 D., 14.0 1.022 278, 555 1. 322 2 18 2. 78 D., 4.7 1. 015

274, 607 1. 309 3 20 2.71 Up, 1.0

.983
265, 408

1.274 21 2.68 Up, 2.2 0.976 263, 960 1. 263 22

2. 76 D., 0.5 0.972 262, 867 1. 259 24 2. 80 D.,12.0

. 948 256, 516

1. 226 25 2. 74 D., 5.0 1. 022 276, 108 1.325 26 2. 74 D., 8.3 0.972 262, 568 1. 256

31 2. 51 Calm. .955 259, 711 1. 250 Sept. 3 2.51 Up, 5.5 1.000 267, 930 1. 290 4 2. 62 D., 1.0 1. 016

273, 923 1. 313 6 8 2. 56 Calm. 1. 0360

279, 007 1.339 12 10 2. 63 Calm. 1.011

272, 633

1. 306 11 2.71 D., 3.7 0.987 266, 647 1. 276 12 2. 56 Up, 4.9 0.936 251, 847 1. 208 14 2.56 Up, 1.3 0.985 263, 153 1. 272 21

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Means.. 2. 97

Mean computed discharge, 271, 673 cubic feet per second.
Mean velocity, 1. 2875 feet per section.
Mean area, 2ii, 000 square feet.

It will be noticed that the force and direction of the wind have a marked effect upon the amount of discharge, and that, except in the Niagara, there is not much change from any other cause, the decrease due to the slight fall in the general level of the river being marked by the wind effect.

The effect of the wind on the discharge, form of curve, &c., has been left for another year, when more observations will be available.

The difference between the mean of the daily discharge from these

tables and that obtained directly from the observations is very small, as will be seen by a comparison of the tables.

The change in the velocity and discharge at Niagara for the season is, however, very marked, and there are daily changes, which do not appear to be due to the wind at the place of observation.

It will be noticed that there are two tables of velocities at this point, one for the first month, and the other for the remainder of the season. These were thus divided, as it was found that during the first period there was but little variation, while during the latter the velocity and discharge rapidly decreased.

In the table of daily discharge are two columns, giving the wind and gauge reading at Buffalo. It will be noticed that the wind at Buffalo appears to have more effect upon the discharge than that recorded at the place of observation, and that the decrease in the discharge follows the fall of the Buffalo guage.

The explanation of this seems to be, that between these two points are the falls of the Niagara, where the whole body of water pours over in a thin sheet, as over a weir, and that a small difference in the depth there would make a large difference in the level below. In fact, Captain Robinson, an old resident of Niagara village, states as the result of his observation that one inch difference of depth on the crest of the fall will make a difference of a foot in the level below.

This seems to be corroborated by the fact that in the winter of 1866–7, when, on account of the water being blown back from the mouth of the river at Buffalo by a strong northeast wind, there was a fall in the level at the ferry dock below the falls of twenty-feet, the difference of depth on the crest of the falls could have been only a small proportion of this, for, except at the apex of the Horseshoe, the depth of water on the crest cannot exceed three or four feet; and though at that time the difference in the amount of water passing the falls was quite perceptible, the crest was not uncovered in any part.

It is very unfortunate that accurate measurements were not taken at that time, as such a large difference rarely occurs.

Between the falls and Lewiston, the points to which steamers can ascend, the river is quite narrow, and therefore very rapid, and the great change of level at the foot of the falls is very much decreased; and at Youngstown, five miles below, where the observations were taken, almost the only effect is seen in the change of velocity, and therefore of discharge, as the river almost immediately widens into the lake, and very little difference of level is perceptible.

Thus we must look to the change of level on the crest of the falls for the difference in the daily discharge.

It will be seen, that when the wind is southwest at Buffalo, thus heaping up the water at the mouth of the river, the discharge is proportionally increased, and vice versa.

Again, the fall of six inches in the Buffalo gauge makes a proportionate decrease on the crest of the falls, thus notably decreasing the discharge.

Besides this decrease, arising from the fall of water at Buffalo, there is, also, during cold weather, a formation of ice above the falls, which has a tendency to check the flow of water.

During the breaking up in the spring, when large quantities of ice are forced into the river from the lake, the water in Lake Erie is rapidly rising, while in the lower part of the river, as shown by the gauge at Fort Niagara, it often remains at a low stage till the latter part of April or May, when it suddenly rises a foot or more in a few days. Therefore we see that though the summer discharge is greater than that at Ogdens

burg, it probably is decreased enough in winter to make the mean for the year sufficiently smaller to allow for the inflow from the water-shed of Lake Ontario.

This also accounts for the slight difference noticed in the last report between the outflow of the Niagara and St. Clair Rivers; for the observations at the former place were taken in August and September, when the discharge had only begun to decrease, and, as is seen in the more extended observations the past year, had become about equal to that of St. Clair.

A few observations in wintzr would be very interesting if it were

We cannot, therefore, at present directly compare the outflow of the possible to take them, but the running ice would make it very difficult. Niagara as observed with that of the other rivers.

In the following table are given the outflow of the several rivers as found by floats in 1867, corrected for difference of level of water and by meter in 1868.

TABLE XIX.-Showing the discharge per second in the different rivers for 1867 and 1868.

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No observations were taken the past year in the Sault River, as it was thought that the float observations could be corrected, so as to compare its outflow with that of the other rivers; but, as before mentioned, the comparisons between the meter and floats are not sufficiently extended to deduce the law of variation. For Niagara the outflow for the first and latter part of the season are given, the latter only comparable with that of 1867, being taken during the same months.

The outflow of 1867, for the St. Clair and St. Lawrence, will be seen to be about ten per cent. too large; this again proves the correctness of the assumption that the floats give too great a velocity.

In Generals Humphreys and Abbot's report on the outflow of the Mississippi, they give the following formula for the computation of the discharge when the mid-depth velocities are known.

Vm= V/D-1 Vbv.
V

= mean velocity of whole river, in which
Vm = mean velocity in each division,
VID=mid depth velocity.
D= depth of river.

1.69
(D-15).
a = area of each division.

A= area of cross section of river. The form of the vertical curve being considered a parabola, the coefficient b was found equal to 0.1856, but in the following tables its value will be found for each depth and is always larger than that amount.

TABLE XX.-Showing the mean velocity as computed by General Humphreys and Abbots mid

depth formula, St. Clair, 1868.

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TABLE XXI.--Showing the mean velocity as computed by Generals Humphreys and Abbot's mid

depth formula, Niagara, 1868.

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1 2 3 4 5 6 7 8 9 10 11

21.00 48. 20 66. 15 70. 95 60. 92 56.00 53. 17 50.00 48. 50 48.50 27. 20

2. 32 2. 23 3. 17 3. 56 3. 59 3. 70 3. 55 3. 44 3. 30 2. 76 2. 06

0.7190 0. 4760 0. 2150 0. 1980 0.2140 0. 2230 0.2290 0.2350 0.2390 0.2390 0. 3160

1, 940 4, 449 6, 106 13, 097 11, 246 10, 338 9, 816 9, 230 8, 953 8,953 3, 516

4, 500 9,921 19, 356 46, 625 40, 373 38, 350 34, 846 31, 751 29, 545 24, 710 7, 242

0.071 0.057 0.037 0.036 0.038 0.039 0.040 0.040 0.041 0.041 0.047

137. 770 253. 593 225. 922 471. 492 427. 348 403. 182 392. 640 369. 200 367. 073 367. 073 165. 252

87, 644

287, 219

3, 580. 545

TABLE XXII.—Showing the mean velocity as computed by Generals Humphreys and Abbot's

mid-depth formula, St. Lawrence, 1868.

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33. 75 62. 28 110.03 177.48 214. 02 232.75 270. 48 381. 30 502, 50 569. 06 567. 34 532. 80 497. 64 500. 20 487. 68 492.70 495. 18 490.80 468. 60 402.60 373. 50 315. 36 223. 86

13 14 15 16 17 18 19 20 21 22 23

Sum..

211, 090

282080.7

1. 0344

8391. 91

Adding together the products of the values of Vm for each division into their respective areas, and parting the sum equal to the mean velocity of the river, multiplied with the total area, we have the following equations, containing V and V2, from which the value of V can be reduced. St. Clair

...66147 V + 2856 . 1V1=223081.7 Niagara

.87644 V + 3580.0 Vi=287219.0 St. Lawrence.

21090 V + 8391 . 9 V1=282080.7 From this, the outflow is obtained by multiplying these velocities by the total areas. This is given below for each river, together with the outflow as obtained directly. It will be seen that the difference is comparatively small. TABLE XXIII.Showing the measured mean velocity and discharge, and the mean velocity and

discharge as computed by Generals Humphreys and Abbot's mid-depth formula, and by the formula containing the velocity at six-tenths the depth.

Mean velocity.

Discharge.

Station.

Computed from

Computed from

Measured.

Measured.

Mid depth.

Six-tenths

depth.

Mid depth.

Six-tenths

depth.

St. Clair.
Niagara.
St. Lawrence.

3. 272
3. 119
1.288

3. 994
3. 203
1. 291

3. 262
3. 150
1. 301

216, 435
273, 329
272, 095

217, 880
280, 757
272, 398

215, 770 276, 079 274, 720

I have not attempted the computation of the outflow by means of the general formula given by Generals Humphreys and Abbot, and as the slope or inclination of the surface of the rivers has not yet been obtained, it is impossible to compare the measured outflow with the general formula for discharge, as they all contain this quality. I expect to obtain this value the coming season.

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