18
2. A similar piece of paper from an illustrated
magazine
Use your microscope at the lowest
magnification and use the preparation of the
daily paper. The letters seen are broken out,
because the newspaper is printed on raw,
inferior paper. Letters of the magazines appear
smoother and more complete. The picture of
the daily paper consists of many small points,
which appear somewhat dirty. The pixels
(raster points) of the magazine appear sharply.
8.2. Textile fibres
Objects and accessories:
1. Threads of different textiles: Cotton, line,
wool, silk, Celanese, nylon etc..
2. Two needles
Each thread is put on a glass slide and frayed
with the help of the two needles. The threads
are dampened and covered with a cover
glass. The microscope is adjusted to a low
magnification. Cotton staples are of vegetable
origin and look under the microscope like a
flat, turned volume. The fibres are thicker and
rounder at the edges than in the centre. Cotton
staples consist primary of long, collapsed
tubes. Linen fibres are also vegetable origin;
they are round and run in straight lines direction.
The fibres shine like silk and exhibit countless
swelling at the fibre pipe. Silk is animal origin
and consists of solid fibres of smaller diameter
contrary to the hollow vegetable fibres. Each
fibre is smooth and even moderate and has the
appearance of a small glass rod. Wool fibres
are also animal origin; the surface consists of
overlapping cases, which appear broken and
wavy. If it is possible, compare wool fibres of
different weaving mills. Consider thereby the
different appearance of the fibres. Experts
can determine from it the country of origin of
wool. Celanese is like already the name says,
artificially manufactured by a long chemical
process. All fibres show hard, dark lines on
the smooth, shining surface. The fibres ripple
themselves/crinkle after drying in the same
condition. Observe the thing in common and
differences.
8.3. Salt water prawns
Accessories:
1. Prawn eggs (Fig 2, 25d)
2. Sea salt (Fig 2, 25c)
3. Prawn breeding plant (Fig 2, 23)
4. Yeast (Fig 2, 25a)
CAREFUL!
Eggs and prawns are not t for
human consumption.
8.3.1 The lifecycle of the saltwater prawn
The saltwater prawn or artimia salina to
scientists has an unusual and interesting
lifecycle. The female‘s eggs are hatched
without any male shrimp having to fertilise
them. The resultant baby prawns are all female.
Under unusual circumstances such as when a
swamp is drained the eggs may produce male
prawns. These males fertilise the female‘s
eggs, resulting in a specific type of eggs. These
are called winter eggs and have a thick shell
as protection. They’re pretty rugged and can
survive the swamp or lake drying out causing
the death of the entire prawn population for up
to a decade in a form of hibernation. The eggs
hatch once the right ambient conditions again
obtain. The eggs supplied (Fig 2, 25d) are of
this type.
8.3.2. Hatching of the salt water prawn
To hatch the prawn it is essential to first have a
saline solution suited to the prawn‘s needs. Fill
half a litre of rain- or fresh-water in a container.
Let it stand for about thirty hours. As water
evaporates over time it‘s a good idea to have
a second container of such water left standing
for thirty-six hours. Once it‘s stood for this
length of time pour half of the sea salt supplied
into one of the containers (Fig 2, 25c) and stir
until it has dissolved. Then pour some of it into
the prawn breeding plant (Fig 2, 23). Add a few
eggs and close the lid. Put it somewhere with
plenty of light but not in the direct sun. The
temperature should be approximately 25° C.
The prawns will hatch in two or three days at
this temperature. Should any water evaporate
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