Facts illustrative of the 



Second pattern measured in length - 1 MOO u^chc> 

 When cast in soft iron - - 10-975 



Contraction • 1 25 

 Equal to l-SSfJ'oth part the length of the pattern. 



The breadth of No. I. was 11 inches, that of No. II. 8|- 

 inches : the thickness in both was -473 inch. 



I shall now finish this paper with some experiments made 

 \ipon the casting of cannon shot. This operation is per- 

 formed by pouring the liquid iron into a mould which is 

 divided into two semi-spheres. The mould is possessed of 

 a joint, which preserves the sphericity of the shot. It is 

 formed by careful turning to gauges made with great care 

 and exactness. This operation exhibits very distmctly the 

 laws of shrinkage, contraction, and expansion ; and from it 

 I mean to prove the truth of what I only before a'ssumed : 

 1st, That cast iron, when fluid, is then more dense than in, 

 any other state : £?d. That immediately upon its passing 

 from the fluid to the solid state it acquires its greatest vo- 

 lume : and 3d, That when cold, and always in proportion 

 to the absence of heat, so will be the diminished diameter 

 of the shot. 



To prove that cast iron is denser in the fluid state, several 

 pieces of iron may be put into a ladle, and hot fluid iron; 

 poured upon them; they will immediately rise to the sur- 

 face, and expose a considerable portion of their bulk above 

 the surface of the liquid iron. This buoyancy diminishes ; 

 and as the pieces of metal approach more and more to the 

 state of fusion that exists in the ladle, they gradually sink, 

 till they disappear entirely under the surface j they then 

 rapidly dissolve, and forni a part of the fluid iron. 



Melted cast iron supports also lead and tin in the same 

 manner ; but these soon become dissipated in the great heat 

 of the fluid . 



If a 6-pounder shot Is placed in the bottom of a 12- 

 pounder mould, or of any size larger, and hot melted metal 

 poured in till the mould is filled, apparently a perfect shot 

 js formed ; but a few blows upon the upj>er part of the 

 sphere, around the gate or runner, detect the surface of the 

 small shot. The thickness of the iron here will not exceed 

 1-lOth of an inch, while the bottom thickness will be nearly 

 a full inch ; and if the mould exceeds in diameter that of 

 a 12-pounder, the inequality of thickness is greater. It is 

 evident from this, that six pounds of fluid iron float six 

 pounds of solid iron in the state of a sphere. That this 

 property is peruianentj may be further understood from a 



continuation 



