[ '8s 3 
The Mcchanifm of the tempering of Glafs Drops, 
applied to that of Steel, is the the moftfimple of all 
the Hypothecs, and anfwcrsall its Properties, which 
are thele : 
i. Tempered Steel has a coarfer Grain. 2. Is is 
increafed in Bulk. 3. It is harder and brittlcr. 4. 
By annealing it becomes lefs brittle. 
Explanation. Steel made red-hot is filled and 
fwelled, and its Pores dilated, by the igneous Matter. 
In this Srate, the cold Water, into which it is thrown, 
comprefies and clofes the Parts of the Surface, while 
the imprifoned igneous Matter dilates the Pores 
within : Thus the Texrure of Steel becomes more 
compad by thele two Caufes, while its Pores are 
dilated. 
Thele large Pores conftitute the coarfe Grain of 
tempered Steel. Its Dilatation by the igneous Mat- 
ter, which could not be thoroughly condenfed by 
the Cold of the Water, caufes its augmented Bulk : 
The clofe Texture of the Subfiance that furrounds the 
Pores, and the imprifoned igneous Matter, occafion 
its Hardncfs and Brittlenefs. Its Rtcodion or An- 
nealing deprives it of this Brittlenefs, and of a Part 
of itsHardnef. : Becaufe it opens thisTexture, which 
it relaxes at the Expence of the neighbouring Pores, 
and drives the igneous Matter out of it. 
Fermentation . 
The Fermentation of Acids and Alkali’s feem, to 
tre to be another Corollary of the fame Principle. 
A a Firjl, 
