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.
front of the condenser of the lantern. A touch of the 
finger will heat the bulb sufficient to cause the drop to 
rise in the tube, and it may be made to descend by 
simply blowing upon the bulb, or by dropping a little 
water or ether upon it. 
Many of the pieces of apparatus for illustrating the 
expansion of metals by heat are so small that they may 
be readily projected. Thus Gravesand’s Ring, Pyrom¬ 
eters, etc. The latter may have a small bit of mirror 
fastened to the end of the index, and the light so 
arranged that as the index rises, the beam will move 
upward. A rise in temperature of only a few degrees 
can be then shown, and the alcohol flame may be dis¬ 
pensed with ; the warmth of the hand or a little hot 
water answering the purpose. 
The condensation of liquid in the form of vapor into 
minute globules and in the production of a shower of 
rain may be very well illustrated and projected for 
class purposes in the following manner : — 
Place about an ounce of Canada balsam in a Flor¬ 
ence flask and make it boil. At the top of the flask 
clouds of globules of turpentine will be seen hovering 
about, altering in shape very much like sky clouds, and 
the globules are large enough to be visible by the naked 
eye. If a cold glass rod be gradually introduced into 
the flask these clouds may be made to descend in 
showers. Lawson Tait in Nature. 
Another: Take a flask of one or two litres capacity ; 
rinse it out with distilled water, and attach to the neck 
a cork and glass tube of about twenty or thirty centi¬ 
metres length. Place the glass tube in the mouth and 


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