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EXPANSION OF IRON, ETC. 383
weight of iron in the mould should not be sufficient to move it. The stand K, bearing an arm J, on which the pointer I was delicately pivoted, was then adjusted so that the needle F should press against the gas carbon D, and the pointer stand at zero on the scale. The long arm of the pointer was 24 inches, and the short one 6 inches long, or as i to 4. The scale was graduated to 1-16 inch.
A, casting; B, fire brick; C, weight; D, gas carbon block; K stand; I, pointer; J, supporting arm; F, adjusting needle.
The mould was filled with very fluid hot iron in 17 secoiids; and then the following results were carefully noted:
For more than i minute after the mould was filled, pointer stood at zero.
At i minute 30 seconds after the mould was filled it moved 1-16.
At i minute 50 seconds after the mould was filled had moved %.
At 3 minutes 10 seconds after the mould was filled had moved ^.
At 5 minutes 20 seconds after ^1;? mould was filled had moved jú.
At 8 minutes 5 seconds after the mould was filled had moved 7-16.
At ii minutes 30 seconds after the mould was filled had moved 15-32.
At 12 minutes 5 seconds after the mould was filled had moved y2.
From that time the pointer stood perfectly still at yz inch until 25 minutes 15 seconds after the mould was filled, when the galvanometer showed that contact with the gas carbon was broken and contraction had begun.
I have made several other equally convincing experiments, but the length of this article forbids that they should be repeated here.
Long before these experiments were instituted the fact that iron follows essentially the same law as water in solidifying was well known and published. I need cite only two authorities: Prof. Edward Turner, in his "Elements of Chemistry, ''published in Philadelphia in 1835, by Desilver, Thomas & Co., says, page 20: "Water is not the only liquid which expands under the reduction of temperature, as the same effect has been observed in a few others which assume a highly crystalline structure in becoming solid; fused iron, antimony, zinc and bismuth arc examples of it." Prof. Thomas Graham, also, in his " Elements of Chem-. 5 o^.