Bauhaus-Universität Weimar

The Book of the Lantern. Being a Practical Guide to the Working of the Optical (or Magic) Lantern. With Full and Precise Directions for Making and Coloring Lantern Pictures.
Hepworth, T. C.
is connected with its own terminal ; these two latter ter¬ 
minals in the cut being lettered bb, and signifying that 
they should be joined up to the battery employed. The 
other two, which are lettered gg, are fastened to the 
terminals on the galvanometer slides. 
In practice it is best for the current reverser to be placed 
on the lecturer’s desk, at some distance from the lantern, 
while the galvanometer slide is joined up by means of tem¬ 
porary wire connexions. The lecturer then has the power 
of reversing the current by touching with his finger either 
of the two treadles, and he can demonstrate in the most 
perfect manner how the different letters in the tele¬ 
graphic alphabet are made up of movements of the needle 
to the right or left, as the case may be. He can also point 
out that the “ dots ” and “ dashes ” of the Morse system 
correspond with these right and left hand movements of 
the magnetic needle. 
In the old days of the Polytechnic Institution in Regent 
Street, which was the resort of so many delighted schoolboys 
and girls, there were several experiments performed with the 
lantern which, so far as I know, have not been repeated 
elsewhere. One of the most curious was the movements of 
the legs of a frog. This is rather a difficult experiment to 
perform, but when well done, is highly effective on the 
At the Polytechnic the frog’s legs covered the large 
screen, and were thus magnified to about 26 feet. The legs 
were hung to a special form of slide, and the nerves and 
muscles of the dead frog were touched with metallic wires, 
when they immediately kicked out in the most startling


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