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A Mechanically simple and low cost subaqueous surface sediment sampler
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 Material Information
Title: A Mechanically simple and low cost subaqueous surface sediment sampler
Series Title: Open file report ;
Physical Description: i, 9 p. : ill. ; 28 cm.
Language: English
Creator: Balsillie, James H
Florida Geological Survey
Publisher: Florida Geological Survey
Place of Publication: Tallahassee, Fla
Publication Date: 2003
 Subjects
Subjects / Keywords: Marine sediments -- Sampling -- Equipment and supplies   ( lcsh )
Sediments (Geology) -- Sampling -- Equipment and supplies   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references.
Statement of Responsibility: by James H. Balsillie.
General Note: Cover title.
 Record Information
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: oclc - 60448102
System ID: UF00099450:00001

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Full Text






State of Florida
Department of Environmental Protection
David B. Struhs, Secretary




Division of Resource Assessment and Management
Edwin J. Conklin, Director


SFlor a e g a urvey.............

aer Sc d State Geologi and Chief






SFw lt-port No. e88


A lechaniay Sinmle and bow Cost
Subi ueou Surface ediment Sampler

by 4

James H. Balsille \





Florida Geological Survey
Tallahassee, Florida
2003
.'. "-. ..: : : _,:.. "+ .-: :: .'
"-'-~ ~, --: --;-",/; "! "













2003:l: :i


ISSN 1058-1391






CONTENTS

Page

A B S T R A C T ..................................................................................................................................... 1
IN T R O D U C T IO N ............................................................................................................................. 1
SAMPLING THE SEDIMENTATION UNIT..................................................................................... 1
SAMPLE SIZE AND SPLITTING................................................................................................. 2
MATERIAL SPECIFICATIONS, DIMENSIONS, AND CONSTRUCTION TIPS ............................2
M ain Barrel.................................................................................................... . .................. 2
Sliding Barrel Stop ...................................................................................................... 3
Sliding Barrel Bushing................................................................................................ 5
S lid ing B arrel .................................................................................................................. 5
B ullet P points ....................................................................................................................... 5
BULLET SAMPLER OPERATION ........................................................................................... 6
ECONOMIC ANALYSIS.......................................... ................................................................ 7
CONCLUSION ..................................................................................................................................... 8
ACKNOWLEDGEMENTS ......................................................................................................... 8
N O TE ........................................................................................................................................ 8
R E FE R E N C ES ................................................................................................................................ 8

LIST OF FIGURES

Figure 1. Basic components of bullet surface sediment sample showing first five-
foot segment (left) with fittings, second five-foot segment main barrel
segment (right) that threads onto the first segment for sampling in water
depths of up to 10 feet, sliding barrel (top middle), and 50-gram and 100-
gram bullet points housing the sediment collection chamber (bottom
m id d le )................................................................................................................................ 3
Figure 2. Schematic of dimensions of the bullet sampler; dimensions are in
inches ......................................................................................................................... 4
Figure 3. The author with a 10-foot length (two five-foot segments ) of the bullet
surface sediment sampler (left) with an additional five-foot segment of main
barrel (right) that can be threaded onto the top of the 10-foot length for
sampling in a water depth of 15 feet............................................................................ 6
Figure 4. Detailed image of tip of the bullet surface sediment sampler showing the
sliding barrel in position for sample collection (to be rotated in a clockwise
direction only), one of two sediment collection slots, and the 100-gram
bullet point sediment collection chamber. Upon extraction of the sampler,
the sliding barrel slips down being stopped by the screw heads in the bullet
point, thereby protecting the sample from being disturbed......................................6
Figure 5. Bullet surface sediment sampler in its carrying case with storage box
open............................................... ............................ ................................... 7





A MECHANICALLY SIMPLE AND LOW COST
SUBAQUEOUS SURFACE SEDIMENT SAMPLER

by

James H. Balsillie, P.G. 167
Florida Geological Survey, 903 W. Tennessee St., Tallahassee FL 32304-7700

ABSTRACT

Over the years the author has developed a subaqueous surface sediment sampler that is simple
to operate and inexpensive to construct. It is designed to be operated in water ranging from wading depths
to a water depth up to 20 feet when operated from a boat. This paper describes (1) sampling rational of the
sedimentation unit for which the device has been designed, (2) sample size constraints for which the
sampler has been configured, (3) sampler specifications, dimensions and construction tips, and (4) sampler
operation.


INTRODUCTION

In 2000, the author completed the
design and construction of a surface sediment
sampling device that can be simply operated in
waist- to chest-deep wading depths or from a
boat. Its origin grew from the desire of not
having to dive for surf zone bottom sediments
during the winter when water temperatures
attain a highly uncomfortable mid-50's degrees
Fahrenheit. The sampling device is currently
designed to allow collection of unconsolidated
sediments from wading depths or from a boat
up to a water depth of 20 feet. Sampling
logistics are eased from a water-depth
perspective, since the device is comprised of
five-foot threaded sections.

The device has specific merits. First, it
can ameliorate or mitigate the water
temperature problem for the sampling individual
where total immersion would be required.
Second, it constitutes a significantly quicker
method requiring fewer personnel for obtaining
a sample than using divers. Third, it allows a
sample to be obtained from a boat in water not
conducive to diving due to potential pollution
problems. Fourth, it much more nearly samples
a sedimentation unit. Fifth, it procures a
sample of a size specifically suited to sieving
analytical procedures.


The purpose of this paper is to
describe the sampling device with the
following specific goals: (1) what it is capable
of sampling, (2) design details and
dimensions to assist the interested researcher
in its construction, and (3) how it is operated.

It is standard practice in scientific
work to express length in S.I. units
(International Systeme d'unites). However, in
the United States, a great many commercially
available products are specified only in British
Imperial units. In fact, construction of the
device described herein could not be
accomplished using S.I. units. Hence, this
work constitutes the rare case where mixed
units are employed to insure clarity and
precision. Mass (weight) is reported in grams.

SAMPLING THE
SEDIMENTATION UNIT

Central to the design of a sampling
device is the question: what is to be
sampled? An underlying assumption with
sedimentologic studies is that the desired field
sample is a lamina sample (Balsillie, 1995).
This is the sedimentation unit of Otto (1938,
p. 575) defined as ... that thickness of
sediment which was deposited under
essentially constant physical conditions.
Apfel (1938, p. 67) used the terminology
phase sampling in which a phase is defined




as ... deposition during a single fluctuation in
the competency of the transporting agency (see
also the work of Jopling, 1964).

Hence, the sedimentation unit or
phase sample represents a narrowly defined
event. For example, it is not deposited by a
flood occurring over a period of several weeks,
but it might be deposited by one energy pulse
occurring over-and-over during the event. Just
what a sedimentation unit, lamina, phase
sample, or bedding plane is in terms of physical
principles, is not known. But, we do recognize
them to some general extent, and regardless of
the unknowns one should strive to collect
sedimentation unit samples (Balsillie, 1995).

Based on observations of bedding
plane characteristics, it was decided that the
sampling device should be designed to collect a
sample no more than 13/32 inches (one
centimeter) in depth. Moreover, the design
purpose of the device was to obtain a bed
surface sample.

SAMPLE SIZE AND SPLITTING

Sample size and sample splitting
where necessary are other important
considerations.

Upon occasion I have prevailed upon
friends and co-workers to secure a sand-sized
sediment sample or two from some exotic
locale to which they were traveling. Even with
specific instructions as to its size, I have
invariably been given a quart-sized or even,
upon occasion, a gallon-sized zip-lock bag filled
with sand. What these individuals fail to realize
is that handling of the sample bag and
vibrations when transported in a vehicle will
further sort a sample. Any sub-sample
collected from such a large sample may well
not represent the original distributive
characteristics of in-place natural material.
Mechanical splitting procedures can be used,
but they too introduce error (e.g., Wentworth,
1926; Swineford and Swineford, 1946;
Sengupta and Veenstra, 1968; Sanford and
Swift, 1971; Emmerling and Tanner, 1974;
Socci and Tanner, 1980; Balsillie, 1995).
Emmerling and Tanner (1974) found as much


as 5% error per split, and recommended no
more than one split where sample archiving is
of importance, say, for litigation purposes.

The bullet surface sediment sampler
is designed to collect a sample of a size
suitable for sieving analysis. No more than
100 grams of sediment should be introduced
to the sieve nest. A larger mass may result in
overcrowding on one or more of the sieves
(e.g., Carpenter and Dietz, 1950; Daescher
and others, 1958; McManus, 1965; de Vries,
1970, Jenke, 1973, Shergold, 1980; Socci
and Tanner, 1980). A sample size of 45
grams is ideal, but can vary from 35 to 50
grams (Socci and Tanner, 1980; Balsillie,
1995). The bullet sampler, then, has been
designed to collect a 50-gram and a 100-
gram sample, bearing in mind that a certain
percentage of the sample will be fluid (salt,
fresh, or polluted water).

MATERIAL SPECIFICATIONS,
DIMENSIONS, AND CONSTRUCTION
TIPS

The bullet sampler has five main
components: (1) main barrel, (2) sliding
barrel stop, (3) sliding barrel bushing, (4)
sliding barrel, and (5) bullet points; see Figure
1 for basic segments, and Figure 2 for design
schematics. Material specifications and
dimensions and construction instructions are
as follows.

Main Barrel

The main barrel is comprised of
two-inch diameter schedule PVC well casing
and bullet points with ASTM F-480 threads
(i.e., two -inch threads per inch for both
male and female threaded ends and an O-
ring for each male threaded end). The main
barrel has an inside diameter (ID) of 1 9/16
inches, and an outside diameter of 1 29/32
inches. It is recommended that well casing
segments five feet in length be used for the
sampler. Well casing can be obtained from a
well drilling supplier.

The first five-foot segment of the
main barrel requires special design



































Figure 1. Basic components of bullet
surface sediment sampler showing first
five-foot segment (left) with fittings,
second five-foot segment main barrel
segment (right) that threads onto the
first segment for sampling in water
depths of up to 10 feet, sliding barrel (top
middle), and 50-gram and 100-gram
bullet points housing the sediment
collection chamber (bottom middle).

considerations. Since the bullet points have
male threads, modifications are made to the
female end of the first main barrel segment.
The lineal length of the threaded sections for
both male and female threads is 1 h inches
from the casing ends. Two slots approximately
1 % inches length are cut across the main
barrel (Figure 1), one each on opposite sides of
the main barrel, at a distance of from 1 Y2
inches to 1 19/32 inches from the female


thread end of the first casing length. This
results in a slot about 13132 inches (i.e., 1.0
cm) in width. These slots are appropriately
beveled to facilitate sediment sample
collection when the main barrel is rotated in
a clockwise direction. A rubber stopper is
inserted into the main barrel flush with the top
of the slots. If snug enough, friction fit will
suffice. If not, it can be secured using epoxy
two-part glue. This insures that upon barrel
removal water draining from the main barrel
will not wash out the collected sample.

All main barrel segments are
perforated with -inch holes at 1 -foot
distances along the main barrel length (all
five-foot segments) to facilitate sampler
immersion and drainage of water when the
main barrel is removed from the water. The
main barrel is also labeled for distances in
British Imperial or S.I. units as desired
beginning at the top of the sediment collection
slots. Horizontal lines perpendicular to the
main barrel axis are made using a fine
triangular file to create shallow grooves which
are then filled with indelible black ink from a
fine felt tip marker. Adhesive-backed
numerals can then be applied to appropriate,
easily recognizable intervals so that water
depths can be easily measured when the
sampler is at its design collection depth.

The first length of the main barrel is
also fitted with the sliding barrel stop and
sliding barrel bushing whose descriptions
follow.

Sliding Barrel Stop

The sliding barrel stop is a piece of
two-inch PVC 1120 schedule (SHD) 40,
ASTM D-1785 pipe (I. D.: 2 3/64 inches; 0.
D.: 2 3/8 inches) that is available from any
hardware retailer. A one- to two-inch piece
will suffice. Cut a vertical kerf with a hack
saw parallel with its length (Figure 2). This
will allow one to easily slide it up the main
barrel to a position where it will precisely stop
the sliding barrel at the top of the
sedimentation collection slots. The sliding
barrel stop is attached to the main barrel










Female (1" 5-foot Section) SLIDING BARREL
Threaded Sediment Collection Slot 2" PVC SCH 40 with STOP Dep
End ASTM F-480 threads Mar


Kerf ,
-- ------ ------- -
L -^ ------------ ^


Rubber Stopper


Screws


Dralnaqe Hole


0 1 2 3 4
Bevel ends of
SEDIMENT
COLLECTION
SLOT


5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Direction of Rotation

End
View


BULLET POINT
(100-gram)


Stainless Steel
Screw Stops


Male
Threaded
/ End


Foot


Center Filled
With Epoxy


Sediment
Collection
Chamber


SLIDING BARREL
2" PVC 1120SCH 40 ASTM D-1785


0 1 2 3 4 5 7 8 9 10 11 13 14 15
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15


Figure 2. Schematic of dimensions of the bullet sampler; dimensions are In Inches.


---------------Balsillie Bullet------------
I Balsillie Bullet_

------


__ I _


SLIDING BARREL BUSHING


MAIN BARREL


>th
ks




first segment using PVC glue and four
stainless steel sheet metal screws.

Sliding Barrel Bushing

Main barrel well casing and two-inch
PVC 1120 SCH 40 ASTM D-1785 used for the
sliding barrel leaves a gap of about 1/16
inches and a sloppy fit. I fitted a piece of clear
plastic tubing with an ID of 1 59/64 inches and
OD of 2 1/32 inches, 10 inches in length to
serve as a bushing to reduce the gap. The
clear plastic tubing was found at a well drilling
supplier and patiently applied by tapping it with
some force into place. The fit in the bullet
sampler was a friction fit. If one uses epoxy
glue, only use it at the top 14 inch of the bushing
and apply it to the main barrel only (i.e., not to
both surfaces).

Sand-sized particles in the bullet
sampler tend to sometimes get lodged between
the bushing and sliding barrel, reducing the
effectiveness of the sliding barrel to protect
the sample from being washed out of the
sample container. From time-to-time the sliding
barrel should be removed and both it and the
bushing washed clean of any adhering
sediment.

Sliding Barrel

The sliding barrel, 14 3/8 inches in
length, is constructed of 2.0-inch PVC 1120
SCH 40 ASTM D-1785 tubing, and a 2 x 3 inch
round PVC area drain with a foot diameter of
close to 6 inches, both readily attainable at your
local hardware retailer. The PVC tubing must
extend entirely through the area drain and be
flush with the 6-inch diameter surface (Figures
1 and 2). The plate of the drain can be
removed and a 2 3/8- inch diameter precisely
centered hole cut using a jig-saw; some
sanding or filing using a rasp may be needed to
"true-up" the fit. Do not use PVC glue to secure
the two pieces, because it will set before the
pieces can be properly aligned. Instead,
position the pieces so that a flush fit is obtained
and at 1200 spacings secure the pieces using
5/16-inch full thread stainless steel sheet metal
screws.


The sliding barrel serves two
important purposes. First, it collects a surface
sample by ensuring that the sampler remains
at the sedimentary bed surface due to the 6-
inch diameter area drain head. Second, upon
extraction the barrel slides downward, to
cover the sample collection slots so that
sample material will not be washed out of the
bullet point sediment collection chamber.

Bullet Points

Bullet points house the sample
collection chamber. I purchased several
points 6 5/8 inches in length. They are
composed of two units, a point and a male
threaded barrel (ASTM F-480 threads) joined
by rivets. Drill out the rivets to separate the
parts. Next, fill the point inside the chamber
with epoxy and let it set and cure; this should
take about eight hours.

Now, the bullet points can be
constructed to collect specific samples sizes
(i.e., masses). I designed two sample sizes, a
50-gram sample and a 100-gram sample.
The first is the optimal size for sieving, the
second if a split is necessary for
archival/litigation purposes. The depth of the
sample collection chamber is made by
shortening the barrel from the non-thread
end. One will need to calibrate the barrel
length required for sediment volumes to be
collected. I use a plastic 35-mm film canister
as a guide. It holds close to slightly less than
50 grams of dry medium-sized quartz sand.
The researcher will have to decide, based on
regional characteristics of average grain sizes
to be sampled and their mineralogic content
and attendant mass densities, the appropriate
sediment collection chamber size.
Construction of two or more chamber sizes is
recommended. Also, the researcher must
include in volume collection considerations,
the volume of fluid that will be part of the
sample collected.

When points and barrels are
assembled they are joined using PVC glue
and two V1 in long stainless steel round head
screws. It is the screw heads which provide
the lower stop for the sliding barrel.






































-Sr




Figure 3. The author with a 10-foot length
(two five-foot segments) of the bullet
surface sediment sampler (left) with an
additional five-foot segment of main
barrel (right) that can be threaded onto
the top of the 10-foot length for sampling
in a water depth of 15 feet.

BULLET SAMPLER OPERATION

The sampler is deployed in the vertical
direction (Figure 3). Vertical pressure is applied
until the sliding barrel is felt to make contact
with the sliding barrel stop (Figure 4). For


Figure 4. Detailed image of tip of the
bullet surface sediment sampler showing
the sliding barrel in position for sample
collection (to be rotated in a clockwise
direction only), one of two sediment
collection slots, and the 100-gram bullet
point sediment collection chamber. Upon
extraction of the sampler, the sliding
barrel slips down being stopped by the
screw heads in the bullet point, thereby
protecting the sample from being
disturbed.

sample collection the sampler main barrel
must be rotated in the clockwise direction
only. If not, one risks unscrewing the bullet
point sample container, thereby losing both it
and the sliding barrel. (Please note that
PVC is neutrally buoyant).

Upon extraction, the user should feel
the sliding barrel make contact with the stop
screws embedded in the bullet point. If
contact is not felt, exert a greater vertical
amount of thrust. It is possible that sand-
sized material caught between the sliding
barrel and sliding barrel bushing is
rendering operation inefficient. In either case,





























storage box open.


continue to extract the sampler, keeping it
vertical. In a secure posture, i.e., so that the
sliding barrel with not drop into the water,
remove the bullet point and secure the sample
in a suitable container. A narrow spatula may
be required to remove the sample. Next,
remove the sliding barrel and wash both it and
the sliding barrel bushing clean. Feel the
sliding barrel bushing from time-to-time. If
burrs are felt, lightly sand it using wet-dry 180-
grit or finer sand paper until smooth.

In wading depths (waist- to chest-deep
water), the first five-foot length of the sampler
should be sufficient for sample collection.
When employed from a boat, vertically insert
the first two segments (i.e., a 10-foot main
barrel section comprised of two five-foot
sections). Thereafter, successively thread on
each additionally required five-foot sections.
Following sample collection, any section greater
than 10 feet in depth (or length) should be
removed while the sampler is in the vertical
position. Bear in mind that the PVC well casing
wall is quite thin at the threads. A 10-foot


section is quite substantial unless mistreated.
Any length beyond that may be vulnerable to
failure if handled in any but the vertical
direction.

ECONOMIC ANALYSIS

The author has, during the past
year, donated the use of the Bullet Sampler in
two Florida Geological Survey projects. To
date 218 samples have been collected in one
project during seven days (6 hours/day) of
field work along Florida's Panhandle and Big
Bend coasts. Shallow water sampling in
depths of 1.5 m (5 feet) or less can be
accomplished by free surface diving.
However, in greater water depths, particularly
where currents are moderate or strong, scuba
divers are required. Even if both shallow and
deeper sampling were to be anticipated in a
project, one should employ scuba divers to
insure continuity in the sampling effort. Local
commercial dive shops were contacted for
quotes on diving rates. While they can vary
considerably, an equitable, competitive, and





relatively low quote of $62.50 per hour was
found.

Two activities sap scuba divers'
strength: (1) working in a current, and (2)
exiting the water and climbing back aboard the
host water craft. Four such episodes constitute
the diver's working day. Hence, for the work
conducted 14, not seven, days of field work
would have been required. In addition, two
divers working together would be required to
satisfy safety standards. Using divers, the 218
samples would have resulted in a commercial
total value of $10,500 dollars or $48.00 per
sample.

During the seven field sampling days,
the author operated the Bullet Sampler. Based
upon his approximate salary, the collection of
218 samples during 42 hours of field work
results in a total cost of $1,050 or $4.80 per
sample. For an entry level employee operating
the Bullet Sampler, the cost could easily be as
low as $2.40 per sample. Hence, the Bullet
Sampler is far more cost effective at less than
1/10 to 1/20 of the standard cost, resulting in
completing the sampling task in half the time.
In one instance, three samples were extracted
15 feet from a sewage processing facility outfall
in 16 feet of water, a task that divers would not
have been particularly happy to perform.

CONCLUSION

This paper describes sampling
rational, sampler specifications, dimensions and
construction, and sampler operation for a
surface sediment sampler costing less than $70
dollars (year 2000 expenditure levels) and a
modicum of tools for its construction. A
carrying case is an additional concem not
covered in this work (Figure 5). The case was
constructed of materials left over from
preceding wood working projects and extracted
no other costs other than design, construction,
and painting.

ACKNOWLEDGEMENTS

The author thanks Dr. William C.
Parker, Department of Geological Sciences,
Florida State University for his encouragement


that this paper be compiled and for
conversations on the topic, and to Dr.
Stephen A. Kish, Department of Geological
Sciences, Florida State University for the
photo images. The author also thanks his
FGS colleagues, Carol Armstrong, Jon Arthur,
Paulette Bond, Ken Campbell, Ron
Hoenstine, Jackie Uoyd, Guy H. Means,
Frank Rupert, Walt Schmidt, and Thomas M.
Scott, for their reviews and comments.

NOTE

The sampling device described in
this work was designed and constructed on
the author's free time extemal to any time as
a State of Florida employee. All material
costs for its construction were incurred by the
author.

REFERENCES


Apfel, E. T., 1938, Phase
sediments: Joumal of
Petrology, v. 8, p. 67-78.


sampling of
Sedimentary


Balsillie, J. H., compiler, 1995, William F.
Tanner on environmental plastic
granulometry: Florida Geological
Survey, Special Publication No. 40,
144 p.

Carpenter, F. G., and Deitz, V. R., 1950,
Methods of sieve analysis with
particular reference to bone char U.
S. National Bureau of Standards
Journal of Research, v. 45, p. 328-
346.

Daeschner, H. S., Siebert, E. E., and Peters,
E. D., 1958, Application of
electroformed precision micromesh
sieves to the determination of particle
size distribution: Symposium on
Particle Size Measurement, American
Society on Testing and Materials
Special Technical Publication No. 234,
p. 26-47.

de Vries, N., 1970, On the accuracy of bed-
material sampling: Journal of
Hydraulic Research, v. 8, p. 523-534.






Emmerling, M., and Tanner, W. F., 1974, Wentworth, C. K., 1926, On mechanical
Splitting error in replicating sand size analysis of sediments: University of
analysis: Program Abstracts, Geological Iowa Studies in Natural History, v. 2,
Society of America, v. 6, p. 352. 52 p.

Jenke, N. C., 1973, Sieve load equations and
estimates of sample size: Journal of
Sedimentary Research, v. 43, p. 518-
520.

Jopling, A. V., 1964, Interpreting the concept of
the sedimentation unit: Journal of
Sedimentary Petrology, v. 34, p. 165-
172.

McManus, D. A., 1965, A study of maximum
load for small diameter screens:
Journal of Sedimentary Research, v. 35,
p. 792-796.

Otto, G. H., 1938, The sedimentation unit and
its use in field sampling: Journal of
Geology, v. 46, p. 569-82.

Sanford, R. B., and Swift, D. J. P., 1971,
Comparison of sieving and settling
techniques for size analysis, using a
Benthos rapid sand analyzer:
Sedimentotogy, v. 17, p. 257-264.

Sengupta, S., and Veenstra, H. J., 1968, On
sieving and settling techniques for sand
analysis: Sedimentology, v. 11, p. 83-
98.

Shergold, L. Z., 1980, The effect of sieve
loading on the results of sieve analysis
of natural sands: Journal of
Sedimentary Research, v. 65, p. 245-
249.

Socci, A., and Tanner, W. F., 1980, Little known
but important papers on grain-size
analysis: Sedimentology, v. 27, p. 231-
232.

Swineford, A., and Swineford, F., 1946, A
comparison of three sieve shakers:
Journal of Sedimentary Petrology, v. 16,
p. 3-13.