348 REPORT OF NATIONAL MUSEUM, 1904. 



thought, ""will never be regarded in this country as appropriate terms 

 Tor our rocks." He recognized the existence of contact phenomena, 

 and also that the degree of crystallization and general structural fea- 

 tures ,of an igneous rock are dependent upon conditions of cooling, 

 though he regarded pumice as being formed when the fused rock, 

 under little pressure, was brought in contact with water. The pos- 

 sibility of the cellular structure being due to expansion of vapor 

 of water in the lava itself was not recognized. The hornblende rock, 

 so extensively developed in Cumberland, Smithfield, and Johnston, he 

 regarded as of igneous origin, and suggested that its apparent strati- 

 form structure might be due to an admixture of the argillaceous slate 

 through which it was elevated. 



The eruptive nature of the Cumberland iron ore was also recognized, 

 though naturally the fact that the rock was an iron-rich peridotite 

 partially altered into serpentine, as later described by Wadsworth, 

 was overlooked. 



The origin of the drift was to him still obscure. Concerning the 

 distribution in the form of bowlders of the iron ore to the southward, 

 above mentioned, he wrote: 



There can not remain a doubt that a violent current of water has rushed over the 

 surface of the State since the elevation and consolidation of all the rocks and subse- 

 quent to the deposition of the tertiary clay, and that this current came from the 

 north. * * * Upon the surface of solid ledges, wherever they have been recently 

 uncovered of their soil, scratches are seen running north and south and the hard 

 rocks are more or less polished by the currents of water which at the diluvial epoch 

 coursed over their surfaces, carrying along the pebbles and sand which effected this 

 abrasion, leaving strise, all of which run north and south, deviating a few degrees 

 occasionally with the changes of direction given to the current by obstacles in its 

 way. 



He did not accept the theory of drifting icebergs, "nor can we 

 allow that any glaciers could have produced them by their loads of 

 sliding rocks, for in that case they should radiate from the mountains 

 instead of following a uniform course along hillsides and through 

 valleys." 



The report was accompanied by six plates of Coal-Measure fossils 

 and a geological map. 



Geological work in Delaware at the expense of the State began and 

 ended with the survey by J. C. Booth, a chemist, during 1837-38. 

 Incidentally, it may be remarked that Mr. Booth's career as a geolo- 

 gist was equally prescribed. 



Booth's Survey fe • -• "1 -• A i *. uv U- ^1 



of Delaware, A unique feature of the act establishing the survey 



was the requirement that an equal portion of the 

 appropriation should be expended in each county, regardless of exist- 

 ing conditions. The clause was presumably inserted to allay local 

 jealousies, but the absurdity of the same is, nevertheless, so great as 

 to leave no room for comment. In the report, which appeared in the 



