Scientific Intelligence. — Geology. 195 



Blanc in height by 1000 feet. These observations agree with 

 those which M. Gay-Lussac made at the same time. The 

 Professor of Casan thinks he may conclude from them, that it 

 is impossible to attribute the magnetic virtue of the globe to the 

 existence of a central metallic nucleus. 



12. Gigantic Jbssil Plant of Craigleith Quarry. — About 

 three years ago, the workmen in this celebrated sandstone quar- 

 ry (from which has been derived nearly all the beautiful free- 

 stone with which the New Town of Edinburgh is built) came 

 accidentally to uncover what seemed to have been the trunk of 

 a lofty tree. It now lay in a position nearly horizontal, and 

 conformable to the dip of the sandstone strata. The colour and 

 consistence of the trunk, or cast resembling a trunk, differed 

 considerably from that of the sandstone in which it was im.-. 

 bedded, and the quarriers easily traced the stem for the length 

 of thirty-six feet. At the base it was about nine feet in circum- 

 ference ; and it continued proportionally thick throughout, only 

 declining slightly in size toward the upper end. It seemed to 

 have been a single, unbranched stem ; at least no certain symp- 

 tom of ramification appeared. The internal structure seemed 

 to be uniform, or without any visible distinction of bark, wood, 

 and pith, or any trace of concentric layers. This singular spe- 

 cimen may therefore be regarded as a gigantic member of the 

 Cyperaceae, or of some other family of the Monocotyledonous 

 tribe, belonging to the earliest Flora of our world. The greater 

 part of this curious specimen was preserved for Mr Ramsay of 

 Bamton, the proprietor of the quarry ; but some fragments 

 were left, and these, fortunately, fell into the hands of the ac- 

 tive and ingenious Mr Witham of Lartington. That gentle- 

 man had thin sections cut, both transverse and longitudinal ; 

 and when these are placed under the microscope, the structure 

 of a monocotyledonous plant is distinctly shewn. Mr Witham 

 sent a fragment to M. Auguste Brongniart, who has made such 

 vegetable lemains his peculiar study ; and he also pronounced 

 the plant to have been monocotyledonous. At Mr Witham's 

 request, likewise, the substance of the stem was submitted to 

 analysis by Mr William Nicol ; and 100 parts gave 



