152 TECHNOLOGY. 
tious qualities. The above machine consists of a cylinder revolving in a 
frame; the cylinder is partially filled with potatoes and revolved until 
the friction has loosened the dirt from them; it is then filled with water, 
or a stream is kept running through it, until it flows clean from the 
machine. 
E.. The Silkworm. 
Silk is an animal production, spun by the so-called silkworm, the larva 
of the Phalena bombyx mori. The animal is furnished with a collection 
of vessels, in which is secreted, about the time of spinning, a glutinous liquid 
which hardens on exposure to the atmosphere, and forms the silk thread, 
which is usually about two thousand feet long, and is strengthened for use 
by doubling. In the raising of the silkworm the first care should be to pro- 
vide the food; many substitutes have been tried for the mulberry, but 
nothing has yet been found to take its place. 
The white mulberry, the leaves of which furnish the best food for the silk- 
worm, is indigenous in Syria, Persia, China, and southern Germany. That 
the leaves may be gathered with ease, the tree should not be permitted to 
grow very tall, but be shortened-in every season, for several years after it 
leaves the nursery. PJ. 32, jig. 31, may be cut in, as seen in fig. 80; the 
following year the branches which it has pushed (fig. 33) are headed down, 
as seen in jig. 32, and so on each succeeding year, as seen in jigs. 34, 35, 
36, and 37, until the tree receives a low bushy form, from which the leaves 
may be easily gathered. Recently the mulberry has been grown in hedges, 
from which the leaves may be gathered without trouble. The Morus mul- 
ticaulis is best adapted to this mode of culture. The rooms in which the 
worms are fed are furnished with shelves one above the other ; or more pro- 
perly removable frames made of plaited willow roots or coarse netting ( pl. 
32, figs. 16 and 17) ; they should be well ventilated, and capable of being 
darkened when required. There should also be arrangements for heating 
the apartments, that an equable temperature may be maintained, and the air 
kept constantly dry; should the air become too dry it may be corrected by 
placing vessels of water in the rooms. 
The first care of the silk-grower is to procure good egos; cocoons are 
selected of a white or yellow color; the female cocoons (pl. 32, jig. 24) 
are rounder in the middle than the male (jig. 25), which have a deeper 
depression in the centre. Equal quantities of both are selected. The 
cocoons inclose the pupa; jig. 26 is the female, jig. 27 the male. A tem- 
perature of 50° to 80° Fahrenheit is necessary to bring them out, and a 
period of two to three weeks is required; this should take place in a tole- 
rably dark room. 
Figs. 28 and 29 are the perfect insect, the former the female, the latter 
the male. Soon after hatching they are permitted to come together. After 
a few days the male dies, and the female, after laying five to six hundred 
eggs, dies also. These eggs are permitted to hatch at a time when the 
young leaves of the mulberry are tender. The eggs (jig. 18) are placed in 
boxes (jig. 15), which in eight or ten days are placed in frames covered 
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