Intelligence and Miscellaneous Articles. 



421 



first some beds below the horizon of the Denbigh Grits at Ffriddfawr 

 which agree very well in their characters with the base of the 

 Coniston Grit, and others near agreeing with the passage-beds 

 between these Grrits and Plags. He next describes sandstones in 

 the Clywedog valley, the equivalents of the lower Grits, and, 

 lastly, at Bod Renail, flags &c, the Pale Slates, which contain Grap- 

 tolites and are thus to be identified with the Graptolitic mudstones 

 of the Lake -district. Thus he is of opinion there is a basement - 

 series here for the Silurian, corresponding in all its details with that 

 in the Lake- district. 



L. Intelligence and Miscellaneous Articles. 



ON THE ALTERATION OF THE DENSITY OF STEEL BY HARDENING 

 AND TEMPERING. BY CARL FROMME. 



"II T BAETTS* has communicated some experiments on the thermo- 

 •^-^ • electric place and the electric conductivity of hardened steel. 

 A comparison of the " thermoelectric hardness " of steel wires 

 hardened at different degrees of heating with the measurements of 

 the specific gravity made on hardened and tempered steel rods and 

 published by met showed a good accordance between the numbers 

 in the two cases. As there only a very brief survey of the results 

 obtained, so far as they appeared necessary for the establishment 

 of an opinion advanced respecting magnetic pheuomena, was given, 

 but measurements of this sort have never, to my knowledge, been 

 communicated, I hold it not superfluous to give here the more pre- 

 cise data furnished by the observations. 



Pour rods were cat from the same larger rod, each 100 millims. 

 long and 7 millims. thick. Table I. contains the specific gravities 

 of the rods, first in the state in which they were procured from the 

 maker (crude), then in the glass-hard state (hardened in cold water), 

 tempered yellow, tempered blue, and grey. 



Table I. 





Rod 1. 



Rod 2. 



Rod 3. 



Rod 4. 



Crude 



Hardened 



Tempered yellow 



,, blue 



78154 

 77420 



7-7789 

 77942 



7-8174 



78188 

 7-7565 

 7-7918 



7-8002 

 7-8227 



7-8128 

 7-7687 

 7-7962 

 7-8054 

 78192 



78200 

 77604 

 77922 

 77994 

 7-8209 



Grey 



Putting the volume of the rod in the crude state equal to 1 , we 

 get :— 



* Wied. Ann. vii. pp. 383-414 (1879). 



t NacTir. d. k. Ges. Wiss. zu Gottingen, 1876, No. 7, p. 165. 



Phil Mag. S. 5. Vol. 8. No. 50. Nov. 1879. 2 F 



