310 
MINUTES OF PROCEEDINGS OF 
The form was not altered in the least., though the heat was raised in the 
last instance to the melting-point, as shown by the lower part of the cylinder 
beginning to melt. 
Experiment 13. A hollow zinc cylinder was heated and cooled by half¬ 
immersion fifty times. 
It was heated in a wood furnace, the degree of heat to which it was 
brought being regulated by the melting of a piece of tin which was conveyed 
at the same time with it into the furnace. Several experiments with pieces 
of tin and zinc had been previously made, by means of which it was ascer¬ 
tained that in the same temperature tin melted in two-sevenths of the time 
requisite to melt zinc; hence when the zinc cylinder and piece of tin were 
placed in the furnace together, the time occupied by the tin in reaching its 
melting-point was carefully noted, and the cylinder was left in the furnace as 
long again as the time thus observed; by this means it was brought very 
nearly to its melting-point without incurring any danger of its actually 
melting. The last five times, however, it was allowed to remain a little 
longer in the flame; and the melting upon the top was retarded the last four 
times by placing a piece of iron upon it, which conducted heat from that 
part, allowing it to remain half a minute longer in the furnace. 
The effect obtained was the same as that produced upon the brass cylinder 
(Exp. 10), or the opposite of what took place with iron; an expansion of 
Eig. 17. 
One-sixth of full size. 
•175 inch occurred upon the water-line, and of T15 inch upon the lower 
edge. 
Experiment 14. The hollow wrought-iron cylinder was heated to redness 
and cooled by half-immersion on its side , instead of on its end as in other 
experiments, twenty times. 
The effect was a very complicated one (see figs. 17,18, and 19); the dotted 
lines show the original form. 
