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Proceedings of the Boyal Society 
4. Why hardened steel has a less sp. gr. than unhardened steel, 
and why it is so brittle % 
5. How tempering is effected ? 
6. How the passage of carbon from one condition to another can 
be accounted for ? 
7. How rehardening takes place 1 
8. How the brittleness of steel is removed by tempering 1 ? 
9. Why hardened steel instruments when used gradually lose 
their hardness h 
10. Why iron containing from 04 to 1*7 per cent, of carbon only 
presents these properties of hardening and more particularly 
of tempering that are peculiar to steel *? 
11. How damascened steel is produced 1 ? 
Steel is regarded as a normal solution of carbon in iron, and cast 
iron as a supersaturated solution, and it is shown how the difference 
between a normal and a supersaturated solution is sufficient to 
account for differences as great as these between steel and cast iron. 
Objections to this hypothesis are then discussed, particularly the 
the two strongest, viz., (1) the production of hydrocarbons when 
hardened steel or white cast iron is dissolved in acids ; and (2) the 
reversed analogy of the copper and tin alloys in favour of the 
physical theory. 
3. Some Physical Experiments bearing upon the Circulation 
of the Blood-Corpuscles. By D. J. Hamilton, M.B., 
E.B.C.S.E., F.B.S.E. 
(Abstract.) 
When the circulation of the blood is observed in the transparent 
tissues of an animal, it is noticed that the coloured corpuscles run 
in the axial part of the stream, while the colourless mostly keep in 
the peripheral still current. The coloured corpuscles move much 
faster than the colourless; they have also a gliding, while the 
colourless have a rotatory, motion. Further, if the frog’s web be 
examined in the upright position, with the microscope inclined so 
as to be horizontal with the table on which it is placed, it is 
noticed that the great majority of the leucocytes not only flow in 
