300 
PROFESSOR J. A. EWING AND Mil. W. ROSENHAIN 
(1) Flakes of lead. 
(2) Clean iron filings. 
(3) Clean sand. 
In all three cases no growth across the weld took place, which confirms the view 
that the presence of a more fusible eutectic in an inter-crystalline boundary is essential 
to crystalline growth across that boundary. We think, therefore, that we are 
justified in regarding the results of these experiments as strong confirmation of 
the solution theory of crystalline growth in annealing. 
Index oe Plates. 
Fig. 2. A general view of an etched surface of sheet-lead, under oblique light, 
magnified 2 diameters. (Plate 3.) 
Figs. 3 and 4. Two photographs of the same area of etched sheet-lead under 
different incidence of oblique light. Magnification 40 diameters. These 
photographs illustrate the appearance of twin lam el he. (Plate 3.) 
Fig. 5. Geometrical markings on etched sheet-lead seen under oblique light and 
magnified 100 diameters. (Plate 4.) 
Fig. 0. A typical view of the structure seen in etched cast-lead under oblique light 
and magnified 12 diameters. (Plate 4.) 
Fig. 7. A typical view of the structure of freshly crushed lead seen under oblique 
light and magnified 30 diameters. (Plate 4.) 
Figs. S to 13. Series of views of a single specimen of crushed lead taken at intervals 
during six months, showing the growth of crystals at the temperature of 
the air, seen under oblique light and magnified 12 diameters. (Plates 5 
and 6.) 
Figs. 14 to 19. Series of views of a single specimen of sheet-lead showing the effect 
of continued exposure to a temperature of 200° C.. seen under oblique light 
and magnified 12 diameters. (Plates G and 7.) 
Figs. 20 to 2G. Series of views of a single specimen of freshly crushed lead showing 
the effects of continued exposure to 200 C. seen under oblique light : 
Nos. 20 to 25 magnified 12 diameters, No. 26 magnified 8 diameters. 
(Plates 8 and 9.) 
Fig. 27. An aggressive crystal developed in crushed lead by annealing, seen under 
oblique light, magnified 8 diameters. (Plate 10.) 
Figs. 29 and 30. Geometrical etched pits seen in tin-plate under vertical light and 
magnified 100 diameters. (Plates 10 and 11.) 
Figs. 28, 31 and 32. Photographs of etched tin-plate as seen by daylight at half the 
natural size. (Plates 10 and 11.) 
