apparatus on campus of university of california.

265 Pages·2011·30.23 MB·English

U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 86 PLATE I
APPARATUS ON CAMPUS OF UNIVERSITY OF CALIFORNIA.
DEPARTMENT OF THE INTERIOR
UNITED STATES ^GEOLOGICAL SURVEY
GEORGE OTIS SMITH, DIRECTOR
PROFESSIONAL PAPER 86 .
THE
TRANSPORTATION OF DEBRIS BY RUNNING WATER
BY
GROVE KARL GILBERT
BASED ON EXPERIMENTS MADE WITH THE ASSISTANCE OF
EDWARD CHARLES MURPHY
WASHINGTON
GOVERNMENT PRINTING OFFICE
1914

CONTENTS.
Page.
Preface.......................................... 9 CHAPTER II. Adjustment of observations........... 55
Abstract......................................... 10 Observations on capacity and slope............ 55
Notation......................................... 13 The observational series................. 55
CHAPTER I. The observations.................... 15 Errors................................... 56
Introduction................................. 15 Intake influences................. .^..... 56
General classification..................... 15 Outfall influences....................... 56
Stream traction.......................... 15 Changes in apparatus.................... 57
Outline of course of experimentation ...... 17 Rhythm................................. 58
Scope of experiments..................... 17 Slopes of de'bris and water surface........ 59
Accessory studies........................ 18 The logarithmic plots.................... 59
Flume traction.......................... 18 Selection of an interpolation formula. .... 60
Apparatus and material........!............. 19 The constant a and competent sloped...... 65
Experiment troughs...................... 19 Interpolation........................... 72
Water supply............................. 19 Precision............................... 73
The water circuit........................ 19 Duty.................................... 74
Discharge................................ 20 Efficiency............................... 75
Sand feed............................... 20 Observations on depth....................... 87
Sand arrester............................ 20 Mode of adjustment...................... 87
Settling tank............................ 21 Precision............................... 94
Gage for depth measurement............. 21 Mean velocity........................... 94
Level for slope measurement............. 21 Formratio............................... 94
Pitot-Darcy gage......................... 21 Graphic computation.................... 94
Sand and gravel.......................... 21 CHAPTER III. Relation of capacity to slope........ 96
Methods of experimentation................... 22 Introduction................................. 96
General procedure for a single experiment. 22 In channels of fixed width................... 96
Details of procedure..................... 22 The conditions..!..........,............. 96
Width of channel.................... 22 The sigma formula...................... 96
Discharge............................ 22 The power function and the index of rela-
The feeding of sand................... 23 tive variation.......................... 97
The collection of sand............... 24 The synthetic index..................... 99
Determination of load................ 24 Application to the sigma function......... 99
Determination of slope............... 25 Variation of the index.................... 104
Contractor........................... 25 Formulation with constant coefficient..... 109
Measurement of depth............... 25 Effect of changing the unit of slope........ 112
Measurement of velocity.............. 26 Precision............................... 113
Modes of transportation...................... 26 Evidence from experiments with mixed
Movement of individual particles......... 26 debris................................. 113
Boiling.............................. 26 Relation of index to mode of traction...... 115
Saltation........................... 26 In channels of similar section................. 116
Collective movement.................... 30 The conditions........................... 116
Units......................................:. 34 Sigma and the index..................... 117
Terms...................................... 35 The synthetic index..................... 119
Load.................................... 35 Summary............................... 120
Capacity................................ 35 Review.................................... 120
Competence.............................. 35 Duty and efficiency......................... 121
Discharge................................ 35 CHAPTER IV. Relation of capacity to form ratio..... 124
Slope.................................... 35 Introduction................................. ]24
Size of debris........................... 35 Selection of a formula....................... 124
Form ratio............................... 35 Maximum............................... 124
Duty and efficiency..................... 36 Capacity and width...................... 125
Symbols................................. 36 Capacity and depth...................... 127
Table of observations on stream traction. ..... 36 Capacity and form ratio................. 128
(cid:9)3
CONTENTS.
Paga. Page.
CHAPTER IV Continued. CHAPTER X. Review of controls of capacity........ 186
Discussion of experimental data.............. 130 Introduction................................. 186
Scope and method of discussion.......... 130 Formulation based on competence............ 186
Sensitiveness and the index of relative vari- The form-ratio factor........................ 190
. ation.................................. 130 Duty and efficiency......................... 192
Control of constants by slope............. 131 The formula of Lechalas..................... 193
Control of constants by discharge......... 132 The formula.........................'.... 193
;" Control of constants by fineness............ 133 Discussion.............................. 194
Special group of observations.............. 134 CHAPTER XI. Experiments with crooked chan
Summary as to control by conditions..... 134 nels .......................................... 196
The optimum form ratio............:........ 135 Experiments................................ 196
Summary...:.'.'V...."............. 1.......... 136 Slope determinations......................... 196
CHAPTER V. Relation of capacity to discharge..... 137 Forms and slopes............................ 197
Formulation and reduction................... 137 Features caused by curvature................. 198
Measures of precision and their interpretation.. 142 CHAPTER XII. Flume traction.................... 199
Control of relative variation by conditions..... 143 The observations............................ 199
Duty and efficiency.............. 1. ^:....... 144 Scope................................... 199
Comparison of the controls of discharge and slope. 145 Grades of debris......................... 199
Controls of capacity..............'........ 145 Apparatus and methods................. 199
Controls of duty..................:...... 147 Processes of flume traction................ 200
Controls of efficiency..................... 148 Movement of individual particles.. . . 200
Summary.................................... 149 Collective movement................ 201
CHAPTER VI. Relation of capacity to fineness of Table of observations.................... 202
debris.......................................... 150 Adjustment of observations................... 203
Formulation................................ 150 Formulation............................ 203
Precision................................... 151 Precision............................... 206
Variation of the constant <f>.................... 153 Discussion.................................. 206
Index of relative variation................... 153 Capacity and channel bed................ 206
Duty and efficiency......................... 154 Capacity and slope....................... 208
Summary................................... 154 Capacity and discharge................... 209
CHAPTER VII. Relation of capacity to velocity.:.. 155 Capacity and fineness.................... 210
Preliminary considerations................... 155 Mixtures:............................... 212
The synthetic index when discharge is constant. 157 Capacity and form ratio................. 213
Mean velocity versus slope................... 158 Trough of semicircular cross section. ..... 214
The synthetic index when slope is constant.... 159 Summary................................ 215
The synthetic index when depth is constant... 160 Competence................................ 215
The three indexes............................. 160 Work of Overstrom and Blue.................. 216
Relative sensitiveness to controls.............. 162 CHAPTER XIII. Application to natural streams. ... 219
Competent velocity........................... 162 Introduction......:.......................... 219
CHAPTER VIII. Relation of capacity to depth...... 164 Features distinguishing natural streams........ 219
Introduction................................. 164 Kinds of streams........................ 219
When discharge is constant. ................. 164 Features connected with curvature of
When slope is constant...................... 164 channel.............................. 220
Depth versus discharge....................... 165 Features connected with diversity of dis
When velocity is constant.................... 165 charge. ............................... 221
The three conditions compared............... 166 Sections of channel...................... 222
Comparison of controls by slope, discharge, and The suspended load..................... 223
mean velocity............................. 167
The two loads........................... 230
CHAPTER IX. Experiments with mixed grades..... 169
Availability of laboratory results............. 233
Adjustment and notation..................... 169
.The slope factor.......................... 233
Mixtures of two grades......................... 172
The discharge factor...................... 233
Control by slope and discharge................ 175
The fineness factor....................... 235
Mixtures of more than two grades.............. 176
The form-ratio factor...................... 236
A natural grade............................. 177
Causes of superior mobility of mixtures........ 178 The four factors collectively.............. 236
Voids....................................... 179 The hypothesis of similar streams......... 236
Fineness................................... 180 Summary.-.............................. 240
Relation of capacity to fineness, for natural Conclusion................................... 240
grades.................................... 180 CHAPTER XIV. Problems associated with rhythm.. 241
Definition and measurement of mean fineness.. 182 Rhythm in stream transportation.............. 241
Summary................................... 184 Rhythm in the flow of water.................. 242
CONTENTS.
Page. Page.
CHAPTER XIV Continued. APPENDIX B. The discharge-measuring gate and its
The vertical velocity curve.................. 244 rating......................................... 257
The moving field............................ 249 The gate..................................... 257
APPENDIX A. The Pitot-Darcy gage.............. 251 Plan of rating............................... 258
Scope of appendix............................ 251 Calibration of measuring reservoir............. 258
Form of instrument........................... 251 The observations.......................... .. 259
Rating methods............................. 252 INDEX. .......................................... 261
Rating formula............................... 253
TABLES.
Page. Page.
TABLE 1. Grades of de"bris...................... 21 TABLE 26. Values of m1} in Coc rf7"1, when slope is
2. Gate readings and corresponding dis constant............................ 128
charges............................. 23 27. Quantities illustrating the influence of
3. Data connected with changes in mode slope on the relation of capacity to form
of transportation..................... 33 ratio................................ 132
4. Observations on load, slope, and depth.. 38 28. Quantities illustrating the influence of
5. Values of capacity generalized from Table discharge on the relation of capacity
4(G)............................... 61 to form ratio......................... 133
6. Data for the construction of curves in 29. Quantities illustrating the influence of
figures 20 and 21 .................... 62 fineness on the relation of capacity to
7. Values of a in C=61(S-<;)n............ 66 form ratio........................... 133
8. Values of a, arranged to show variation 30. Quantities illustrating the influence of
in relation to fineness of debris........ 68 slope and discharge on the,relation of
9. Experimental data on competent slope.. 69 capacity to form ratio ............... 134
10. Experimental data on competent dis- 31. Estimated ratios of depth to width to
charge.............................. 70 enable a given discharge, on a given
11. Values of a, as adjusted for use in inter slope, to transport its maximum load. 135
polation equations................... 72 32. Data on the relation of capacity to dis
12. Adjusted values of capacity, duty, and charge .............................. 137
efficiency.......................... 75 33. Values of «, computed from data of
b'
Table 32............................ 140
13. Values of nt in d= ................. 89
Adjusted system of values of K. ......... 141
& u4.
14. Adjusted values of depth of current, with 35. Values of i3, arranged to show variation
values of mean velocity and form ratio. 89 in relation to fineness............... 144
15. Values of i, in relation to slope......... 100 35. Comparison of ^ with i3................ 145
16. Values of;, in C=cS'i................. 109 37. Variations of ij and i3 in relation to dis
17. Values of i, for mixtures of two or more charge .............................. 146
grades.............................. 114 33 Variations of \ and i3 in relation to width. 146
18. Comparison of values of ir for mixtures 39. Variations of i^ and i3 in relation to fine
and their components................ 115 ness ................................ 147
19. Values of it associated with the smooth 40. Variations of ij and iz in relation to slope. 147
mode of traction .................... 115
Variations of the ratio - ............ 148
20. Relations of ^ to discharge, debris grade,
and channel width.................. 116 i,-l
Variations of the ratio 148
21. Selected data showing the relation of ca L-l
pacity to slope when the form ratio is 43. Yalues of capacity, arranged to illustrate
constant............................ 117 the relation of capacity to grades of
22. Values of a corresponding to data in debris.............................. 150
Table 21............................ 118 44. Data connected with the plots in fig
23. Values of synthetic index under condi ure 50.............................. 151
tion that R is constant, and under con- ' 45. Values of 74, compared with slope, dis
dition that w is constant............. 119 charge, and width................... 154
23a. Comparison of (parameters in C=&! 46. Values of IVQ .......................... 157
(S-a)n and E=f^ (S-a)nu. ....... 123 47. Means based on Table 46, illustrating the
24. Relation of capacity to width when control of IVQ by discharge, fineness,
slope and depth are constant......... 126 and width.......................... 158
25. Values of capacity and depth for grade 48. Synthetic indexes, comparing the con
(C), width 0.66 foot, and slope 1.0 per trol of capacity by mean velocity with
cent............................... 128 the control by slope................. 158
CONTENTS.
Page. Page.
TABLE 49. Values of IVS- ........................ 159 TABLE 66. Relative speeds of coarse and fine de"-
50. Means based on Table 49, illustrating bris in flume traction .....:........... 200
the control of TVS by slope, fineness, . 67. Observations on flume traction, showing
and width .......................... 159 the relation of load to slope and other
51. Values of Ira ......................... 160 conditions.......................... , 202
52. Means based on Table 51, illustrating the 68. Values of capacity .for flume traction, ad
control of Iva by fineness and width.. 160 justed in relation to slope............. 204
53. Comparison of synthetic indexes for ca 69. Comparison of capacities associated with
pacity and mean velocity, under the different characters of channel bed.... 206
several conditions of constantdischarge, 70. Values of /! for flume traction........... 208
constant depth, and constant slope.... 161 71. Comparison of values of II for flume trac
54. Values of Ids......................... 164 tion with corresponding values for
55. Means based on Table 54, illustrating stream traction....................... 209
the control of las by slope, fineness, 72. Data illustrating the relation of capacity
and width.......................... 165 for flume traction to discharge........ 209
56. Synthetic indexes comparing the control 73. Values of capacity for flume traction,
of capacity by depth with control by illustrating the control of capacity by
discharge........................... 165 fineness.............................. 210
57. Values of lav ......................... 165 74. Capacities for mixed grades and their
58. Means based on Table 57, illustrating the components......................... 212
control of lav by mean velocity, fine 75. Depths and form ratios of unloaded
ness, and width..................... 166 streams.............................. 213
59. Comparison of synthetic indexes for ca 76. Capacities for flume traction in troughs
pacity and depth under the several of different widths .................. 213
conditions of constant discharge, con 77. Data on flume traction in a semicylindric
stant slope, and constant mean velocity 167
" trough............................ 1.. 214
60. Adjusted values of capacity for mixtures
78. Observations by Blackwell on velocity
of two or more grades of d6bris....... 169
competent for traction................ 216
61. Capacities for traction, with varied mix
79. Values of n in Coc Vmn based on Blue's
tures .of two grades............... r.. 172
experiments.."...................... 218
62. Percentages of voids in certain mixed
80. Velocities of streams with and without
grades of debris ...................... 179
tractional loads....................... 230
63. Fineness of mixed grades and their com
ponents............................. 180 81. Ratio of the suction at one opening of the
63a. Data on subaqueous dunes of the Loire. 194 Pitot-Darcy gage to the pressure at the
64. Comparison of slopes required for straight other............................... 254
and crooked channels................ 197 82. Values of KanduinH-H^KV" ..... 254
65. Grades of debris....................... 199 83. Values of A in V= A^H-I^........... 255
ILLUSTRATIONS.
Page. Page.
PLATE I. Apparatus on campus of the University FIGUKE 10. Longitudinal section illustrating the
of California.................... Frontispiece. dune mode of traction.............. 31
II. Debris used in experiments............. 22 11. Longitudinal section illustrating the
III. Rough surfaces used in experiments on antidune mode of traction...........
flume traction........................ 200 12. Profiles of water surface, automatically
FIGURE 1. Diagrammatic view of shorter experi recorded, showing undulations asso
ment trough......................... 19 ciated with the antidune mode of
2. Diagram of water circuit.............. 20 traction............................ 33
3. The contractor........................ 25
13. Plot of a single series of observations of
4. Diagrammatic view of part of experi
capacity and slope................. 55
ment trough with glass panels and
14. Logarithmic plot of a series of observa
sliding screen....................... 27
tions on capacity and slope......... 56
5. Appearance of the zone of saltation.... 27
15. Diagrammatic longitudinal section of
6. The beginning of a leap, in saltation. . 28
outfall end of experiment trough,
7. Diagram of accelerations affecting a
saltatory grain..................... 28 illustrating influence of sand arrester
8. Theoretic trajectory of a saltatory par on water slope..................... 57
ticle. ............................. 29 16. Diagrammatic longitudinal section of
9. Ideal transverse section of zone of sal debris bed and stream, in a long
tation at side of experiment trough.. 30 trough............................. 57
CONTENTS.
Page. Page.
FIGURE 17. Diagrammatic longitudinal section of FIGURE 43. Eelation of capacity, C, to form ratio","
outfall end of trough, illustrating R. The variation of the function
influence of contractor............. C=bi(l+aR)Rm with slope......... 131
18. Profiles of channel bed, illustrating 44. Relation of capacity, C, to form ratio,
tractional rhythms associated with R. The variation of the function
dunes of greater magnitude......... 58 C=b2(l-aR)Rm with discharge..... 132
19. Logarithmic graph of C=f(S), for grade 45. Relation of capacity, C, to form ratio,
(G), w=0.66 foot, Q==0.734 ft.3/sec... 61 R. The variation of the function
20. Extrapolated curves of C=f(S) for vari C=6a(l-f*R)Rm with fineness of d6-
ous tentative equations of interpola bris................................ 133
tion and for slopes greater than 2.4 46. Relation of capacity, C, to form ratio,
per cent............................ 62 i-'-::R. The variation of the function
21. Extrapolated curves of C=f(S) for vari \ i'G=^(\ fxK)Rm with slope and dis
ous tentative equations of .interpola charge. ............................ 134
tion and for slopes less than 0.8 per 47. Logarithmic plots of the relation of
cent............................... 63 ;.-capacity to discharge................ 139
22. The relation of a in C=f(S-a) to the 48. Ideal cross section of a stream in the ex-
curvature of the logarithmic graph.. 65 < periment trough, illustrating the rela
23. Diagrammatic sections of laboratory tion of competent discharge to width. 140
troughs, illustrating relation of cur 49. Logarithmic plot of *=/(!>)........... 141
rent depth to trough width......... 67 50. Logarithmic plots of capacity,for trac
24. Ideal curve of competent slope in rela tion in relation to fineness of debris.. 150
tion to width of trough .............. 67 51. Average departures of original values
25. Logarithmic plot of competent slope in of capacity from system of -values
relation to fineness of de'bris........ 69 readjusted in relation to fineness of
26: Illustration of the method used to ad ..debris.............................. 152
just values of capacity in relation to 52. Vertical velocity curve, drawn to illus
slope by means of a logarithmic plot trate its theoretic character near the
of observed values of capacity in re stream's bed......................... 155
lation to slope minus a............. 72 53.. Ideal profile of a stream bed composed
27. Observations of depth of current in re of de'bris grains..................... 155
lation to' slope..................... 87 54. Ideal curves of velocity in relation to
28. Logarithmic computation sheet, com depth, illustrating their relation to
bining relations of capacity, mean the zone of saltation................ 161
velocity, form ratio, and slope...... 95 55. Tractional capacity for mixed debris,
29. Logarithmic locus of the exponential .in relation to proportions of compo
equation.......................... 98 nent grades, with associated curves of
30. Locus of log j/=/(log x), illustrating the fineness and of percentages of voids.. 173
nature of the index of relative varia 56. Tractional capacities of components of
tion. ............................... 98 mixed grades in relation to the
31. Variations of i, in relation to slope..... 105 percentages of the components in the
32. Variations of i, in relation to width of mixtures........................... 174
channel........................... 106 57. Curves of capacity in relation to slope
33. Variations of i, in relation to discharge. 107 for grade (A), grade (G), and mixtures
34. Variations of i, in relation to fineness of of those grades..................... 175
de'bris.............................. 108 58. Curves of capacity in relation to slope
35. Variations of exponents ilt jl; and k in for grade (B), grade (F), and mixtures
relation to slope..................... 113 of those grades..................... 175
36. Variations of ij under conditions of uni 59. Curves of capacity in relation to slope
form mode <5f traction and uniform for grade (C), grade (E), and mixtures
slope............................... 116 of those grades..................... 176
37. Curves of C f(S) for three trough 60. Curves of capacity in relation to slope
widths............................. 118 for a mixture of five grades, (C, D, E,
38. Illustration of the relation of capacity F, G). Comparison of mixture curves
to width of channel and to form ratio,
for three discharges and of mixture
when slope and discharge are constant 124
curve with curves for component
39. Cross sections of stream channels....... 125
grades ............................ 176
40. Capacity for traction in relation to
61. Capacity-slope curves for related mix
width of channel, when depth and
tures and capacity-discharge curves
slope are constant.................. 127
for mixture and component grades.. 177
41. Plot of equation (55).................. 129
62. Capacity-slope curves for a natural
42. Logarithmic plots of
grade of d6bris, compared with curves
2\ ~ p m-t-1 130 for sieve-separated grades........... 178
CONTENTS.
Page. Page.
FIGURE 63. Curves showing the relations of various FIGURE 78. Modification of vertical velocity curve
quantities to the proportions of fine when mean velocity is increased by
and coarse components in a mixture of change of slope...................... 245
two grades of debris, (C) and (G).... 179 79. Modification of vertical velocity curve
' 64. Logarithmic plots of capacity in relation when mean velocity is increased by
to linear fineness, for related mixtures change of discharge.................. 246
of debris........................... 181 80. Modification of vertical velocity curve
65. Curve illustrating the range and dis by changes in the roughness of the
tribution of finenesses in natural and channel bed........................ 246
artificial grades of debris............. 181 81. Modification of vertical velocity curve
66. Typical curves illustrating the distri by addition of load to stream, with
bution of the sensitiveness of capacity corresponding increase of slope...... 246
for traction to various controlling con 82. Modification of vertical velocity curve
ditions............................ 191 by addition and progressive increase .
67. Plans of troughs used in experiments to of load............................. 246
83. Ideal longitudinal section of a stream,
show the influence of bends on trac
illustrating hypothesis to account
tion................................ 196
for the subsurface position of the level
68. Contoured plat of stream bed, as shaped
of maximum velocity.-.............. 248
by a current....................... 198
84. Diagrammatic plan of suggested mov
69. Curves illustrating the relation of ca
ing-field apparatus................... 250
pacity for flume traction to fineness
85. Longitudinal section of lower end of
of debris........................... 211
receiver of Pitot-Darcy gage No. 3,
70. Diagram of forces...................... 224
with transverse sections at three
71. Interference by suspended particle
points.............................. 251
with freedom of shearing............ 226
86. Cross section of prism of water in trough,
72. Suggested apparatus for automatic feed
showing positions given to gage open
of debris........................... 241
ing in various ratings................ 255
73. Modification of vertical velocity curve
87. Graphic table for interpolating values of
by approach to outfall............... 244
74. Modification of vertical velocity curve A \nV=A -JH H1} for observations
by approach to contracted outfall.. 245 made with gage 3b in different parts
75. Plan of experiment trough with local of a stream.......................... 256
contraction........................ 245 88. Arrangement of apparatus connected
76. Profile of water surface in trough shown with the rating of the discharge-
in figure 75......................... 245 measuring gate..................... 257
77. Modification of vertical velocity .curve 89. Elevation and sections of gate for the
by local contraction of channel...... 245 measurement of discharge........... 258
PREFACE.
Thirty-five years ago the writer made a work as well as for the discussion of results
study of the work of streams in shaping the here contained, while Mr. Murphy is responsible
face of the land. The study included a for the experimental work. It must not be
qualitative and partly deductive investigation understood, however, that in assuming responsi
of the laws of transportation of d6bris by bility for the discussion I also claim sole credit
running water; and the limitations of such for what is novel in the generalizations. Many
methods inspired a desire for quantitative conclusions were reached by us jointly during
data, such as could be obtained only by our association, and others were developed by
experimentation with determinate conditions. Mr. Murphy in his report. These have been
The gratification of this desire was long de incorporated in the present report, so far as
ferred, but opportunity for experimentation they appeared to be sustained by the more
finally came in connection with an investigation elaborate analysis, and specific credit is given
of problems occasioned by the overloading of only where I found it practicable to quote
certain California rivers with waste from from Mr. Murphy's manuscript.
hydraulic mines. The physical factors of Mr. J. A. Burgess was for a short time a
those problems involve the transporting capac scientific assistant in the laboratory, and his
ity of streams as controlled by various condi work is described in another connection.
tions. The experiments described in this Credit should be given to Mr. L. E. Eshleman,
report were thus instigated by the common carpenter, and Mr. Waldemar Arntzen, mechan
needs of physiographic geology and hydraulic ician, for excellent work in the construction of
engineering. apparatus., I recall with sincere gratitude
A laboratory was established at Berkeley, the cordial cooperation of several members of
Cal., and the investigation became the guest the university faculty, and the investigation is
of the University of California, to which it is especially indebted to the good offices and
indebted not only for space, within doors and technical knowledge of Prof. S. B. Christy
without, but for facilities of many kinds most and Prof. J. N. Le Conte.
generously contributed. Portions of my manuscript were read by
Almost from the beginning Mr. E. C. Murphy Dr. R. S. Woodward and Dr. Lyman J. Briggs,
has been associated with me in the investigation and the entire manuscript was read by Mr. C. E.
and has had direct charge of the experiments. Van Orstrand and Mr. Willard D. Johnson.
Before the completion of the investigation I To these gentlemen and to members of the
was compelled by ill health to withdraw from editorial staff of the Geological Survey I am
it, and Mr. Murphy not only made the remain indebted for criticisms and suggestions leading
ing series of experiments, so far as had been to the elimination of some of the crudities of
definitely planned, but prepared a report. the original draft.
This report did not include a full discussion of While the aid which my work has received
the results but was of a preliminary nature, from many colleagues lias been so kindly and
it being hoped that the work might be con efficient that individual mention seems invid
tinued, with enlargement of scale, in the near ious, my gratitude must nevertheless be
future. When afterward I found myself able expressed for valuable assistance by Mr. Fran-
to resume the study, there seemed no im 9013 E. Matthes in the examination of foreign
mediate prospect of resuming experimentation, literature, and for the unfailing encouragement
and it was thought best to give the material and support of Mr. M. 0. Leighton, until
comparatively full treatment. It will readily recently in charge of the hydrographic work
be understood from this account that I am of the Survey.
responsible for the planning of the experimental G. K. G.