Phil. Mag. Ser. 6, Vol. 7, Pl. I. 
Fie. 6. 
Dattenberg bars No.1 (2nd & 3rd heatings) ; No. 2 (Ist heating.) 
eG Gouge 4 6 8 400 2 4 6 § 500 2 4 6 8$ 6002 4 6 8 702 4 6 8 800 
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