Bauhaus-Universität Weimar

The Art of Projecting. A Manual of Experimentation in Physics, Chemistry, and Natural History with the Porte Lumière and Magic Lantern
Dolbear, A. E.
working in front of the lens, the same as with the 
porte lumière. • 
The following is a list of apparatus and of experi¬ 
ments which are suitable for such projection : Equil¬ 
ibrium of the same liquid in several communicating 
vessels; equilibrium of different liquids in communi¬ 
cating vessels ; cartesian diver ; the hydrometer ; cap¬ 
illarity ; diffusion of gases ; Torricelli’s experiment ; 
Mariotte’s law ; the manometer ; SprengePs air pump ; 
fountain in vacuo ; the siphon ; the pyrometer ; the in¬ 
fluence of pressure upon the boiling point ; M. Des- 
pretz’s experiment on the conductivity of solids ; con¬ 
vection ; the thermo-pile ; umbra and penumbra ; action 
of magnets ; attraction and repulsion from electrical ex¬ 
citation. Natural history specimens, such as birds, rats, 
mice, squirrels, frogs, toads, live fishes, if in a tank with 
transparent sides ; leaves of trees, ferns, etc. ; well-de¬ 
fined crystals, such as quartz, feldspar, mica, pyrite ; 
diagrams on glass of machinery, as the steam engine— 
these diagrams can be drawn a foot square or more ; 
silhouettes, etc., etc., are all available with this method. 
There is an advantage in this plan, when it is at all 
applicable, that will 'commend itself to every one, 
namely, it is available at any point between the focus 
and the screen, hence it will only be necessary to place 
the object in the path of the rays to the screen at such 
a point as will be convenient and will make the shadow 
sufficiently large. The instructor can stand by the ob¬ 
ject, and with a pointer like a pencil call attention to 
any particular part. And again, the field is so large 
that several objects can be in it at a time, if need be, 
for comparison, such for instance as leaves of several 
species of oaks or maples, or a range of capillary tubes 
of various diameters.


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