Large Pinaceous Stems in front of the Herbarium. 53 



some as an essential cliaracteristic of tlic mineral ; but the 

 sections were amorphous, though one out of several exhibited 

 dotted vessels, — a good reason for the palaiontologist to 

 classify the trunks as of pinaceous origin. It is clearly not 

 the bark of the tree. But no trace of vegetation or stony 

 matrix remains in the stems, these being cleu^-ly examples 

 of fossilisation b}^ replacement. Curiously enough, how- 

 ever, they are not composed of the stone forming the bulk 

 of the quarries, but mostly of a ferruginous dolomite, con- 

 taining mainly salts of lime and magnesia, together with 

 a small percentage of the carbonate of the protoxide of 

 iron. All the specimens left on analysis a residuum of 

 vegetable charcoal; in the Redhall specimen it amounted 

 to 3*25 per cent., — this appears to be all that remains of 

 the original wood of the stem. The presence of the dolo- 

 mite was easily traceable in the pervading sandstones of 

 the quarries, not only in the immediate proximity of the fossil 

 stems, but also here and there, in small patches, all through 

 the beds worked. The small quartz crystals, constituting 

 when segregated more than one of our local sandstones, 

 may have had their origin in hydrothermal agencies. In- 

 deed, in the sandstones at Millerhill, and in the Caulm- 

 stone quarry at Salisbury Crags, the crystals are so 

 prominent as to suggest such an origin to a casual observer, 

 rather than being sand-grains of former sea-beaches. If 

 this hydrothermal activity were intermittent, so far as the 

 constituent salts in solution, we would then have all the 

 conditions necessary for the fossilisation of these trunks. 

 Sir Robert claims the action of such alkaline waters for 

 the subtraction of the woody tissues of these trunks ; the 

 woody charcoal and the coal is accounted by a process 

 analogous to that when woody matter is charred in close 

 vessels at a low temperature, the woody matter in this case 

 coming either from the interior of the stem or from below 

 the sandstone stratum. So far, then, the matter is dismissed 

 with some doubt as a provisional hypothesis. In a careful 

 analysis of the sedimentary rocks on Salisbury Crags, appar- 

 ently Sandstones, by external inspection, have exhibited 

 in varying degree the dolomitic constitution of the interior 

 of tlie fossil trunks.* Manj^ chemical geologists accept 



* Trmis. Ed. Geo. Sor.. vol. iii. p. 289. 



