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AND 
BOSTON JOURNAL OF CHEMISTRY. 
Volume XXIV. 
BOSTON, DECEMBER, 1890. 
Number 12. 
CONTENTS. 
Familiar Science. — Two Remarkable Spiders 
An Ancient Gallo-Roman Sepulchre . . . 
Spectroscopic Measures of Stellar Motions . 
Scientific Brevities 
Practical Chemistry and the Arts. — Gly- 
cerine 
Silver 
Industrial Memoranda 
The Out-Door World. — A Retrospect and a 
Prospect 
Astronomical Society of the Pacific . . . 
A Card of Introduction 
A Brave Deed 
Reports from Chapters • . 
Chapter Addresses, New and Revised 
Observations in Natural History — Summer 
of 1890 
Editorial. — A Mediicval Cyclone .... 
The British Association at Leeds .... 
Brief Studies in Biology 
Paris Letter 
Meteorology for October, 1890 
Astronomical Phenomena for December, 
Another "Magnetic" Man .... 
(Questions and Answers 
Literary Notes 
1890 
Medicine and Pharmacy. — Koch's Consump- 
tion Cure 
Appendicitis 
Monthly Summary of Medical Progress . . 
Publishers' Column 
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192 
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Banjiliar Scieijce. 
TWO REMARKABLE SPIDERS. 
The ^ft'^'a^t'c^'P, or trap-door spiders, are 
a widely-scattered species, and are particu- 
I larly remarkable for the wonderful nests 
j which they build instead of spinning a web. 
i The Cteniza Californica, popularly known 
as the tarantula, digs a hole in the ground, 
about an inch in diameter, and from two 
i inches to a foot in depth. It is lined on the 
I inside with a fine, soft silk, spim by the 
; spider, and the mouth, which is slightly en- 
larged, is clo.sed by a cover which moves on 
a silken hinge, and fits so closely to the open- 
ing, when closed, that not even a knife-blade 
■ can be inserted between it and the sides of 
the tube. This cover is made of dirt fastened 
together with threads, and, although lined 
with the silk on the inside, is covered on the 
outside with sand, dirt, moss, etc., so that it 
exactly resembles the surrounding soil and is 
almost impossible to discover. In addition, 
the under side of the cover is provided with 
small holes, into which the spider inserts her 
claws, and by which she can hold it down so 
firmly that it is impossible to raise it without 
tearing. In these nests the spiders live, only 
coming out in search of prey. The eggs are 
laid and hatched in the nest, which serves as 
a nursery for the young spiders till they are 
old enough to go out and dig for themselves. 
Fig. I. 
The shape and construction of the.se nests 
varies greatly with different species. The 
genus Aiypus extends the silken lining of the 
tube .several inches outside the ground, where 
it rests among the stones and jMants ; other 
spiders make a second door, halfway down 
the nest ; others build the nest with a branch, 
or chamber, into which they can retreat if an 
enemy succeeds in forcing the outer entrance. 
This chamber is sometimes closed by another 
trap-door, and sometimes communicates with 
the air by a concealed opening. The Afy- 
galidce are certainly most remarkable animals, 
and their constructive skill — which exceeds 
that of many men — is hard to account for. 
The idea of "instinct" explains nothing, but 
is simply equivalent to saying that we don't 
know ; and the source of their wonderful 
knowledge must be left for future investiga- 
tors to discover. 
The Arg-yronetes, or water-spiders, are 
even more extraordinary in their habits than 
their earth-dwelling cousins. Although they 
are true air-breathing animals like other 
spiders, for' some unaccountable reason they 
prefer to live under the water among the 
fishes, where they spin a web in the shape 
of a bag, with the opening on the under side, 
just like a diving-bell, and, having filled it 
with air, they lay their eggs and bring up 
their young in their cosy subaqueous home, 
finding plenty of food in the insects which 
live among the aquatic plants. The body 
of these spiders is covered with fine hairs, 
which prevent the water from touching the 
body, and, by their total reflection of light, 
give them a silvery appearance when in the 
water — whence their name. 
The manner in which this spider fills her 
nest with air is most curious. After spinning 
the threads, the spider goes to the surface 
of the water, and, by a quick movement of 
the hind legs, catches a small bubble of air 
between them and the abdomen, with which 
she descends to the nest, into which it is 
liberated. After this process has been pa- 
tiently repeated many times, the nest becomes 
full of air, and is ready for occupancy. The 
illustration (Fig. 2) shows two of these nests 
completed, and the spiders in various posi- 
tions above and below the water. 
Fig. 2. 
It must not be supposed that these nests as 
constructed are perfectly air-tight. The small 
meshes are quite sufficient to retain the air- 
