Coherence, Transition, “Flow”
Repeating, or “echoing” key words from preceding
sentences is one of the most powerful tools you have
for achieving “flow.”
The basic technique is to “echo” a key word in the
previous sentence toward the beginning of the new
sentence.
Actually, there are two kinds of sequencing methods
(“flow” methods):
 Continuous focus
 Shifting focus
Continuous focus
Used to call this “static” focus, but “static” is
pejorative:
Mars is the fourth planet from the Sun in our solar
system and is named after Mars, the Roman god of
war. Mars is also known as the "Red Planet" due to
its reddish appearance when seen from Earth. The
prefix areo-, from the Greek god of war, Ares,
refers to Mars in the same way geo- refers to
Earth. Mars has two moons, Phobos and Deimos, which
are small and oddly-shaped.
Barely stifled yawns greeted the electronics
novelty that was introduced to the public in mid1948. "A device called a transistor, which has
several applications in radio where a vacuum tube
ordinarily is employed, was demonstrated for the
first time yesterday at Bell Telephone
Laboratories," noted an obviously unimpressed New
York Times reporter on page 46 of the day's issue.
To be sure, the gadget had plusses. Not only could
the transistor amplify electric current like a
vacuum tube, it also used little power, didn't need
to warm up, and was compact—a thimble-sized
cylinder with a couple of protruding wires. But
because its main ingredient was an expensive, hardto-handle element called germanium, the transistor
seemed likely to remain a laboratory curiosity.
Shifting focus
Used to call this “dynamic,” but “dynamic” makes it
sound superior, which it’s not.
A solar cell (or a "photovoltaic" cell) is a
semiconductor device that converts photons from the
sun (solar light) into electricity. To achieve this
conversion, the device needs to fulfill only two
functions. One function involves photogeneration of
charge carriers (electrons and holes) in a lightabsorbing material. The other function involves
separation of the charge carriers to a conductive
contact that will transmit the electricity. The
result of the functions is called the photovoltaic
effect, and the field of research related to solar
cells is known as photovoltaics.
The most important part of a solar heating system
is the solar collector whose main function is to
heat water to be used in space heating. There are
various types of collectors. However, the flatplate collector is the most common and the focus of
the following discussion. A flat-plate collector
consists of a box-shaped black plate absorber
covered by one or more transparent layers of glass
or plastic with the sides and the bottom of the box
insulated. These layer of glass or plastic have an
intervening air space that produces the heattrapping effect. Water is heated as it circulates
through or below the absorber component, which is
heated by solar radiation.
Topic strings
These sequences of topics are known as topic strings:
some are continuous; others are shifting. Which to
use depends on what you are writing about.
Mars
Mars
Mars
Mars
novelty
transistor
gadget
transistor
transistor
solar collector
types
flat-plate collector
layers
heat
Transition words
In some cases, you cannot echo a preceding topic in a
natural way. When that occurs, my theory is that we
use transition words such as (but not limited to!)
“however,” “therefore,” “for example,” or “in other
words.”
Analyzing topic strings
When you have this way of analyzing coherence, you
can see why some discussions—perfectly
grammatical ones—are more difficult to follow than
necessary:
1 The development of the transistor goes back to the
nineteenth century.
2 Germanium and silicon, along with a number of other
crystalline materials, are semiconductors, so-called
because they neither conduct electricity well, like most
metals, nor block it effectively, as do insulators such as
glass or rubber.
3 Back in 1874 a German scientist named Ferdinand Braun
identified a surprising trait of these on-the-fence
substances: Current tends to flow through a semiconductor
crystal in only one direction.
4 This phenomenon, called rectification, soon proved
valuable in wireless telegraphy, the first form of radio
communication.
5 When electromagnetic radio waves traveling through the
atmosphere strike an aerial, they generate an alternating
(two-way) electric current.
6 However, earphones or a speaker must be powered by direct
(one-way) current.
7 Methods for making the conversion, or rectification, in
wireless receivers existed in the closing years of the 19th
century, but they were crude.
8 In 1899 Braun patented a superior detector consisting of
a semiconductor crystal touched by a single metal wire,
affectionately called a "cat's whisker."
9 His device was popular with radio hobbyists for decades,
but it was erratic and required much trial-and-error
adjustment.