Coal (Bituminous) 1·256
„ (Anthracite) { 1·436
{ 1·640
Charcoal ·441
Brick 1·900
Clay 1·930
Common Soil 1·984
Emery 4·000
Glass (plalte) 3·248
Ivory 1·822
Grindstone 2·143
Diamond 3·521
Gypsum 2·168
Lime 2·720
Granite 2·625
Marble 2·708
Mica 2·800
Millstone 2·484
Nitre 1·900
Porcelain 2·385
Phosphorus 1·770
Pumice Stone ·915
Salt 2·130
Sand 1·800
Slate 2·672
Sulphur 2·033