48 



Prof. J. Prestwich. 



Table of Thermal Conductivities of Rocks, compiled from the Tables 

 of Professors Herschel and Lebour. 



Nature of root. 



Crystalline 

 and Volcanic - 

 rocks. 



Schistose | 

 rocks and -\ 

 Slates. i 



Sandstones. 



Limestones, 

 Oolites, &c. 



Argillaceous 

 strata. 



Mineral 



Granite (mean of five 

 varieties) . 



Porphyry (Germany) 



Porphyritic trachyte 



Basalt (Loch Katrine) 



Trap (Calton Hill) . . 



Serpentine 



Gneiss (Germany) . . 



Mica schist (Scotland) 



Slates (three varieties) . 

 „ (across cleavage) 



Clay-slate (two varieties 



Quartzite 



Ganister sandstone 



Craig] eith „ 



Hard sandstones . . 



Micaceous flagstone 

 (along cleavage). 



Micaceous flagstone 

 (across cleavage). 



Soft red sandstone .... 



New red sandstone . . . . 

 „ „ wet. 



Firestone (Upper Green- 

 sand) . 



Quartzose sand 



„ „ wet 



Statuary marble 



Devonian „ 



Carboniferous limestone 



Magnesian 



Oolite (Ancaster) 



Lias (building stone) . . 



Chalk 



Coal-measure shale .... 



Clay (sun-dried) 



„ (the same wet and 

 soft). 



White quartz 



Alabaster 



Rock salt 



Coal (Newcastle) 



Cannel coal 



Absolute 

 thermal con 

 ductivity, 

 7c. 



0-00584 



00513 

 00590 

 00560 

 00352 

 00515 

 00514 

 00520 

 00561 

 00395 

 00327 

 00954 

 00630 

 00947 

 00672 

 00690 



00492 



00397 

 00250 

 00600 

 00240 



00105 

 00820 

 00530 

 00645 

 00550 

 00522 

 00370 

 00360 

 00220 

 00235 

 00250 

 00350 



00957 

 00360 

 01280 

 00068 

 00120 



Absolute 

 tbermal 

 resistance. 

 r. 



172' 



203' 



252 



Average. 



7c. 



-00562 



-00475 



-00531 



-00734 



0-00323 



-00172 



-00561 



-00242 



178 



221 



190 



139 



252 



180 



411 



Or dividing this series into groups corresponding with the nature of 

 the rocks in the several Tables of underground temperatures, the 

 results are as under : — 



