This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
A short time ago I found it necessary to melt some silver, and in setting up an arc light to obtain the heat I made a rheostat by winding wire around a large earthenware jar. As the jar is a non-conductor and would not burn, it served the purpose perfectly. In winding the wire, be careful to keep the coils from touching each other. - Contributed by P. D. Merrill, Chicago, Ill.